Document:

<PAGE>   1
                                                                   Exhibit 10.10

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                             BUSINESS LOAN AGREEMENT

<TABLE>
<CAPTION>
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PRINCIPAL            LOAN DATE       MATURITY       LOAN NO     CALL    COLLATERAL  ACCOUNT   OFFICER  INITIALS
<S>                  <C>            <C>           <C>           <C>     <C>         <C>       <C>      <C>
$5,000,000.00        11-30-1998     11-30-1999    3400069949     10                 111721      274
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</TABLE>
References in the shaded area are for Lender's use only and do not limit the
applicability of this document to any particular loan or item.
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BORROWER:  BIOSOURCE TECHNOLOGIES, INC.           LENDER: SIERRAWEST BANK
           (TIN:  77-0154648)                             CENTRAL PACIFIC REGION
           3333 VACA VALLEY PARKWAY, SUITE 1000           1100 TEXAS ST.
           VACAVILLE, CA  95688-9412                      FAIRFIELD, CA  94533
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THIS BUSINESS LOAN AGREEMENT BETWEEN BIOSOURCE TECHNOLOGIES, INC. ("BORROWER")
AND SIERRAWEST BANK ("LENDER") IS MADE AND EXECUTED ON THE FOLLOWING TERMS AND
CONDITIONS. BORROWER HAS RECEIVED PRIOR COMMERCIAL LOANS FROM LENDER OR HAS
APPLIED TO LENDER FOR A COMMERCIAL LOAN OR LOANS AND OTHER FINANCIAL
ACCOMMODATIONS, INCLUDING THOSE WHICH MAY BE DESCRIBED ON ANY EXHIBIT OR
SCHEDULE ATTACHED TO THIS AGREEMENT. ALL SUCH LOANS AND FINANCIAL
ACCOMMODATIONS, TOGETHER WITH ALL FUTURE LOANS AND FINANCIAL ACCOMMODATIONS FROM
LENDER TO BORROWER, ARE REFERRED TO IN THIS AGREEMENT INDIVIDUALLY AS THE "LOAN"
AND COLLECTIVELY AS THE "LOANS." BORROWER UNDERSTANDS AND AGREES THAT: (a) IN
GRANTING, RENEWING, OR EXTENDING ANY LOAN, LENDER IS RELYING UPON BORROWER'S
REPRESENTATIONS, WARRANTIES, AND AGREEMENTS, AS SET FORTH IN THIS AGREEMENT; (b)
THE GRANTING, RENEWING, OR EXTENDING OF ANY LOAN BY LENDER AT ALL TIMES SHALL BE
SUBJECT TO LENDER'S SOLE JUDGMENT AND DISCRETION; AND (c) ALL SUCH LOANS SHALL
BE AND SHALL REMAIN SUBJECT TO THE FOLLOWING TERMS AND CONDITIONS OF THIS
AGREEMENT.

TERM. This Agreement shall be effective as of November 24, 1998, and shall
continue thereafter until all Indebtedness of Borrower to Lender has been
performed in full and the parties terminate this Agreement in writing.

DEFINITIONS. The following words shall have the following meanings when used in
this Agreement. Terms not otherwise defined in this Agreement shall have the
meanings attributed to such terms in the Uniform Commercial Code. All references
to dollar amounts shall mean amounts in lawful money of the United States of
America.

    AGREEMENT. The word "Agreement" means this Business Loan Agreement, as this
    Business Loan Agreement may be amended or modified from time to time,
    together with all exhibits and schedules attached to this Business Loan
    Agreement from time to time.

    BORROWER. The word "Borrower" means BIOSOURCE TECHNOLOGIES, INC.. The word
    "Borrower" also includes, as applicable, all subsidiaries and affiliates of
    Borrower as provided below in the paragraph titled "Subsidiaries and
    Affiliates."

    COLLATERAL. The word "Collateral" means and includes without limitation all
    property and assets granted as collateral security for a Loan, whether real
    or personal property, whether granted directly or indirectly, whether
    granted now or in the future, and whether granted in the form of a security
    interest, mortgage, deed of trust, assignment, pledge, chattel mortgage,
    chattel trust, factor's lien, equipment trust, conditional sale, trust
    receipt, lien, charge, lien or title retention contract, lease or
    consignment intended as a security device, or any other security or lien
    interest whatsoever, whether created by law, contract, or otherwise.

    ERISA. The word "ERISA" means the Employee Retirement Income Security Act of
    1974, as amended.

    EVENT OF DEFAULT. The words "Event of Default" mean and include without
    limitation any of the Events of Default set forth below in the section
    titled "EVENTS OF DEFAULT."

    GRANTOR. The word "Grantor" means and includes without limitation each and
    all of the persons or entities granting a Security Interest in any
    Collateral for the Indebtedness, including without limitation all Borrowers
    granting such a Security Interest.

    GUARANTOR. The word "Guarantor" means and includes without limitation each
    and all of the guarantors, sureties, and accommodation parties in connection
    with any Indebtedness.

    INDEBTEDNESS. The word "Indebtedness" means and includes without limitation
    all Loans, together with all other obligations, debts and liabilities of
    Borrower to Lender, or any one or more of them, as well as all claims by
    Lender against Borrower, or any one or more of them; whether now or
    hereafter existing, voluntary or involuntary, due or not due, absolute or
    contingent, liquidated or unliquidated; whether Borrower may be liable
    individually or jointly with others; whether Borrower may be obligated as a
    guarantor, surety, or otherwise; whether recovery upon such Indebtedness may
    be or hereafter may become barred by any statute of limitations; and whether
    such Indebtedness may be or hereafter may become otherwise unenforceable.

    LENDER. The word "Lender" means SierraWest Bank, its successors and assigns.

    LOAN. The word "Loan" or "Loans" means and includes without limitation any
    and all commercial loans and financial accommodations from Lender to
    Borrower, whether now or hereafter existing, and however evidenced,
    including without limitation those loans and financial accommodations
    described herein or described on any exhibit or schedule attached to this
    Agreement from time to time.

    NOTE. The word "Note" means and includes without limitation Borrower's
    promissory note or notes, if any, evidencing Borrower's Loan obligations in
    favor of Lender, as well as any substitute, replacement or refinancing note
    or notes therefor.

    PERMITTED LIENS. The words "Permitted Liens" mean: (a) liens and security
    interests securing Indebtedness owed by Borrower to Lender; (b) liens for
    taxes, assessments, or similar charges either not yet due or being contested
    in good faith; (c) liens of materialmen, mechanics, warehousemen, or
    carriers, or other like liens arising in the ordinary course of business and
    securing obligations which are not yet delinquent; (d) purchase money liens
    or purchase money security interests upon or in any property acquired or
    held by Borrower in the ordinary course of business to secure indebtedness
    outstanding on the date of this Agreement or permitted to be incurred under
    the paragraph of this Agreement titled "Indebtedness and Liens"; (e) liens
    and security interests which, as of the date of this Agreement, have been
    disclosed to and approved by the Lender in writing; and (f) those liens and
    security interests which in the aggregate constitute an immaterial and
    insignificant monetary amount with respect to the net value of Borrower's
    assets.

    RELATED DOCUMENTS. The words "Related Documents" mean and include without
    limitation all promissory notes, credit agreements, loan agreements,
    environmental agreements, guaranties, security agreements, mortgages, deeds
    of trust, and all other instruments, agreements and documents, whether now
    or hereafter existing, executed in connection with the Indebtedness.

<PAGE>   2

11-30-1998                   BUSINESS LOAN AGREEMENT
LOAN NO. 3400069949               (Continued)                             PAGE 2
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    SECURITY AGREEMENT. The words "Security Agreement" mean and include without
    limitation any agreements, promises, covenants, arrangements, understandings
    or other agreements, whether created by law, contract, or otherwise,
    evidencing, governing, representing, or creating a Security Interest.

    SECURITY INTEREST. The words "Security Interest" mean and include without
    limitation any type of collateral security, whether in the form of a lien,
    charge, mortgage, deed of trust, assignment, pledge, chattel mortgage,
    chattel trust, factor's lien, equipment trust, conditional sale, trust
    receipt, lien or title retention contract, lease or consignment intended as
    a security device, or any other security or lien interest whatsoever,
    whether created by law, contract, or otherwise.

CONDITIONS PRECEDENT TO EACH ADVANCE. Lender's obligation to make the initial
Loan Advance and each subsequent Loan Advance under this Agreement shall be
subject to the fulfillment to Lender's satisfaction of all of the conditions set
forth in this Agreement and in the Related Documents.

    LOAN DOCUMENTS. Borrower shall provide to Lender in form satisfactory to
    Lender the following documents for the Loan: (a) the Note, (b) Security
    Agreements granting to Lender security interests in the Collateral, (c)
    Financing Statements perfecting Lender's Security Interests; (d) evidence of
    insurance as required below; and (e) any other documents required under this
    Agreement or by Lender or its counsel.

    BORROWER'S AUTHORIZATION. Borrower shall have provided in form and substance
    satisfactory to Lender properly certified resolutions, duly authorizing the
    execution and delivery of this Agreement, the Note and the Related
    Documents, and such other authorizations and other documents and instruments
    as Lender or its counsel, in their sole discretion, may require.

    PAYMENT OF FEES AND EXPENSES. Borrower shall have paid to Lender all fees,
    charges, and other expenses which are then due and payable as specified in
    this Agreement or any Related Document.

    REPRESENTATIONS AND WARRANTIES. The representations and warranties set forth
    in this Agreement, in the Related Documents, and in any document or
    certificate delivered to Lender under this Agreement are true and correct.

    NO EVENT OF DEFAULT. There shall not exist at the time of any advance a
    condition which would constitute an Event of Default under this Agreement.

REPRESENTATIONS AND WARRANTIES. Borrower represents and warrants to Lender, as
of the date of this Agreement, as of the date of each disbursement of Loan
proceeds, as of the date of any renewal, extension or modification of any Loan,
and at all times any Indebtedness exists:

    ORGANIZATION. Borrower is a corporation which is duly organized, validly
    existing, and in good standing under the laws of the State of California and
    is validly existing and in good standing in all states in which Borrower is
    doing business. Borrower has the full power and authority to own its
    properties and to transact the businesses in which it is presently engaged
    or presently proposes to engage. Borrower also is duly qualified as a
    foreign corporation and is in good standing in all states in which the
    failure to so qualify would have a material adverse effect on its businesses
    or financial condition.

    AUTHORIZATION. The execution, delivery, and performance of this Agreement
    and all Related Documents by Borrower, to the extent to be executed,
    delivered or performed by Borrower, have been duly authorized by all
    necessary action by Borrower; do not require the consent or approval of any
    other person, regulatory authority or governmental body; and do not conflict
    with, result in a violation of, or constitute a default under (a) any
    provision of its articles of incorporation or organization, or bylaws, or
    any agreement or other instrument binding upon Borrower or (b) any law,
    governmental regulation, court decree, or order applicable to Borrower.

    FINANCIAL INFORMATION. Each financial statement of Borrower supplied to
    Lender truly and completely disclosed Borrower's financial condition as of
    the date of the statement, and there has been no material adverse change in
    Borrower's financial condition subsequent to the date of the most recent
    financial statement supplied to Lender. Borrower has no material contingent
    obligations except as disclosed in such financial statements.

    LEGAL EFFECT. This Agreement constitutes, and any instrument or agreement
    required hereunder to be given by Borrower when delivered will constitute,
    legal, valid and binding obligations of Borrower enforceable against
    Borrower in accordance with their respective terms.

    PROPERTIES. Except as contemplated by this Agreement or as previously
    disclosed in Borrower's financial statements or in writing to Lender and as
    accepted by Lender, and except for property tax liens for taxes not
    presently due and payable, Borrower owns and has good title to all of
    Borrower's properties free and clear of all Security Interests, and has not
    executed any security documents or financing statements relating to such
    properties. All of Borrower's properties are titled in Borrower's legal
    name, and Borrower has not used, or filed a financing statement under, any
    other name for at least the last five (5) years.

    LITIGATION AND CLAIMS. No litigation, claim, investigation, administrative
    proceeding or similar action (including those for unpaid taxes) against
    Borrower is pending or threatened, `and no other event has occurred which
    may materially adversely affect Borrower's financial condition or
    properties, other than litigation, claims, or other events, if any, that
    have been disclosed to and acknowledged by Lender in writing.

    TAXES. To the best of Borrower's knowledge, all tax returns and reports of
    Borrower that are or were required to be filed, have been filed, and all
    taxes, assessments and other governmental charges have been paid in full,
    except those presently being or to be contested by Borrower in good faith in
    the ordinary course of business and for which adequate reserves have been
    provided.

    LIEN PRIORITY. Unless otherwise previously disclosed to Lender in writing,
    Borrower has not entered into or granted any Security Agreements, or
    permitted the filing or attachment of any Security Interests on or affecting
    any of the Collateral directly or indirectly securing repayment of
    Borrower's Loan and Note, that would be prior or that may in any way be
    superior to Lender's Security Interests and rights in and to such
    Collateral.

    BINDING EFFECT. This Agreement, the Note, all Security Agreements directly
    or indirectly securing repayment of Borrower's Loan and Note and all of the
    Related Documents are binding upon Borrower as well as upon Borrower's
    successors, representatives and assigns, and are legally enforceable in
    accordance with their respective terms.

    COMMERCIAL PURPOSES. Borrower intends to use the Loan proceeds solely for
    business or commercial related purposes.

    EMPLOYEE BENEFIT PLANS. Each employee benefit plan as to which Borrower may
    have any liability complies in all material respects with all applicable
    requirements of law and regulations, and (i) no Reportable Event nor
    Prohibited Transaction (as defined in ERISA) has occurred with respect to
    any such plan, (ii) Borrower has not withdrawn from any such plan or
    initiated steps to do so, (iii) no steps have been taken to terminate any
    such plan, and (iv) there are no unfunded liabilities other than those
    previously disclosed to Lender in writing.

<PAGE>   3
11-30-1998                   BUSINESS LOAN AGREEMENT
LOAN NO. 3400069949               (Continued)                             PAGE 3
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    LOCATION OF BORROWER'S OFFICES AND RECORDS. Borrower's place of business, or
    Borrower's Chief executive office, if Borrower has more than one place of
    business, is located at 3333 VACA VALLEY PARKWAY, SUITE 1000, VACAVILLE, CA
    95688-9412. Unless Borrower has designated otherwise in writing this
    location is also the office or offices where Borrower keeps its records
    concerning the Collateral.

    INFORMATION. All information heretofore or contemporaneously herewith
    furnished by Borrower to Lender for the purposes of or in connection with
    this Agreement or any transaction contemplated hereby is, and all
    information hereafter furnished by or on behalf of Borrower to Lender will
    be, true and accurate in every material respect on the date as of which such
    information is dated or certified; and none of such information is or will
    be incomplete by omitting to state any material fact necessary to make such
    information not misleading.

    SURVIVAL OF REPRESENTATIONS AND WARRANTIES. Borrower understands and agrees
    that Lender, without independent investigation, is relying upon the above
    representations and warranties in extending Loan Advances to Borrower.
    Borrower further agrees that the foregoing representations and warranties
    shall be continuing in nature and shall remain in full force and effect
    until such time as Borrower's Indebtedness shall be paid in full, or until
    this Agreement shall be terminated in the manner provided above, whichever
    is the last to occur.

AFFIRMATIVE COVENANTS, Borrower covenants and agrees with Lender that, while
this Agreement is in effect, Borrower will:

    LITIGATION. Promptly inform Lender in writing of (a) all material adverse
    changes in Borrower's financial condition, and (b) all existing and all
    threatened litigation, claims, investigations, administrative proceedings or
    similar actions affecting Borrower or any Guarantor which could materially
    affect the financial condition of Borrower or the financial condition of any
    Guarantor.

    FINANCIAL RECORDS. Maintain its books and records in accordance with
    generally accepted accounting principles, applied on a consistent basis, and
    permit Lender to examine and audit Borrower's books and records at all
    reasonable times.

    ADDITIONAL INFORMATION. Furnish such additional information and statements,
    lists of assets and liabilities, agings of receivables and payables,
    inventory schedules, budgets, forecasts, tax returns, and other reports with
    respect to Borrower's financial condition and business operations as Lender
    may request from time to time.

    INSURANCE. Maintain fire and other risk insurance, public liability
    insurance, and such other insurance as Lender may require with respect to
    Borrower's properties and operations, in form, amounts, coverages and with
    insurance companies reasonably acceptable to Lender. Borrower, upon request
    of Lender, will deliver to Lender from time to time the policies or
    certificates of insurance in form satisfactory to Lender, including
    stipulations that coverages will not be cancelled or diminished without at
    least ten (10) days' prior written notice to Lender. Each insurance policy
    also shall include an endorsement providing that coverage in favor of Lender
    will not be impaired in any way by any act, omission or default of Borrower
    or any other person. In connection with all policies covering assets in
    which Lender holds or is offered a security interest for the Loans, Borrower
    will provide Lender with such loss payable or other endorsements as Lender
    may require.

    INSURANCE REPORTS. Furnish to Lender, upon request of Lender, reports on
    each existing insurance policy showing such information as Lender may
    reasonably request, including without limitation the following: (a) the name
    of the insurer; (b) the risks insured; (c) the amount of the policy; (d) the
    properties insured; (e) the then current property values on the basis of
    which insurance has been obtained, and the manner of determining those
    values; and (f) the expiration date of the policy. In addition, upon request
    of Lender (however not more often than annually), Borrower will have an
    independent appraiser satisfactory to Lender determine, as applicable, the
    actual cash value or replacement cost of any Collateral. The cost of such
    appraisal shall be paid by Borrower.

    OTHER AGREEMENTS. Comply with all terms and conditions of all other
    agreements, whether now or hereafter existing, between Borrower and any
    other party and notify Lender immediately in writing of any default in
    connection with any other such agreements.

    LOAN PROCEEDS. Use all Loan proceeds solely for Borrower's business
    operations, unless specifically consented to the contrary by Lender in
    writing.

    TAXES, CHARGES AND LIENS. Pay and discharge when due all of its indebtedness
    and obligations, including without limitation all assessments, taxes,
    governmental charges, levies and liens, of every kind and nature, imposed
    upon Borrower or its properties, income, or profits, prior to the date on
    which penalties would attach, and all lawful claims that, if unpaid, might
    become a lien or charge upon any of Borrower's properties, income, or
    profits. Provided however, Borrower will not be required to pay and
    discharge any such assessment, tax, charge, levy, lien or claim so long as
    (a) the legality of the same shall be contested in good faith by appropriate
    proceedings, and (b) Borrower shall have established on its books adequate
    reserves with respect to such contested assessment, tax, charge, levy, lien,
    or claim in accordance with generally accepted accounting practices.
    Borrower, upon demand of Lender, will furnish to Lender evidence of payment
    of the assessments, taxes, charges, levies, liens and claims and will
    authorize the appropriate governmental official to deliver to Lender at any
    time a written statement of any assessments, taxes, charges, levies, liens
    and claims against Borrower's properties, income, or profits.

    PERFORMANCE. Perform and comply with all terms, conditions, and provisions
    set forth in this Agreement and in the Related Documents in a timely manner,
    and promptly notify Lender if Borrower learns of the occurrence of any event
    which constitutes an Event of Default under this Agreement or under any of
    the Related Documents.

    OPERATIONS. Maintain executive and management personnel with substantially
    the same qualifications and experience as the present executive and
    management personnel; provide written notice to Lender of any change in
    executive and management personnel; conduct its business affairs in a
    reasonable and prudent manner and in compliance with all applicable federal,
    state and municipal laws, ordinances, rules and regulations respecting its
    properties, charters, businesses and operations, including without
    limitation, compliance with the Americans With Disabilities Act and with all
    minimum funding standards and other requirements of ERISA and other laws
    applicable to Borrower's employee benefit plans.

    INSPECTION. Permit employees or agents of Lender at any reasonable time to
    inspect any and all Collateral for the Loan or Loans and Borrower's other
    properties and to examine or audit Borrower's books, accounts, and records
    and to make copies and memoranda of Borrower's books, accounts, and records.
    If Borrower now or at any time hereafter maintains any records (including
    without limitation computer generated records and computer software programs
    for the generation of such records) in the possession of a third party,
    Borrower, upon request of Lender, shall notify such party to permit Lender
    free access to such records at all reasonable times and to provide Lender
    with copies of any records it may request, all at Borrower's expense.

    COMPLIANCE CERTIFICATE. Unless waived in writing by Lender, provide Lender
    at least annually and at the time of each disbursement of Loan proceeds with
    a certificate executed by Borrower's chief financial officer, or other
    officer or person acceptable to Lender, certifying that the representations
    and warranties set forth in this Agreement are true and correct as of the
    date of the certificate and further certifying that, as of the date of the
    certificate, no Event of Default exists under this Agreement.

<PAGE>   4

11-30-1998                   BUSINESS LOAN AGREEMENT
LOAN NO. 3400069949               (Continued)                             PAGE 4
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    ENVIRONMENTAL COMPLIANCE AND REPORTS. Borrower shall comply in all respects
    with all covenants, terms, conditions and provisions set forth in the
    Environmental Indemnity Certificate and Agreement executed in connection
    with the Loan.

    ADDITIONAL ASSURANCES. Make, execute and deliver to Lender such promissory
    notes, mortgages, deeds of trust, security agreements, financing statements,
    instruments, documents and other agreements as Lender or its attorneys may
    reasonably request to evidence and secure the Loans and to perfect all
    Security Interests.

NEGATIVE COVENANTS. Borrower covenants and agrees with Lender that while this
Agreement is in effect, Borrower shall not, without the prior written consent of
Lender:

    INDEBTEDNESS AND LIENS. (a) Except for trade debt incurred in the normal
    course of business and indebtedness to Lender contemplated by this
    Agreement, create, incur or assume indebtedness for borrowed money,
    including capital leases, (b) except as allowed as a Permitted Lien, sell,
    transfer, mortgage, assign, pledge, lease, grant a security interest in, or
    encumber any of Borrower's assets, or (c) sell with recourse any of
    Borrower's accounts, except to Lender.

    CONTINUITY OF OPERATIONS. (a) Engage in any business activities
    substantially different than those in which Borrower is presently engaged,
    (b) cease operations, liquidate, merge, transfer, acquire or consolidate
    with any other entity, change ownership, change its name, dissolve or
    transfer or sell Collateral out of the ordinary course of business, (c) pay
    any dividends on Borrower's stock (other than dividends payable in its
    stock), provided, however that notwithstanding the foregoing, but only so
    long as no Event of Default has occurred and is continuing or would result
    from the payment of dividends, if Borrower is a "Subchapter S Corporation"
    (as defined in the Internal Revenue Code of 1986, as amended), Borrower may
    pay cash dividends on its stock to its shareholders from time to time in
    amounts necessary to enable the shareholders to pay income taxes and make
    estimated income tax payments to satisfy their liabilities under federal and
    state law which arise solely from their status as Shareholders of a
    Subchapter S Corporation because of their ownership of shares of stock of
    Borrower, or (d) purchase or retire any of Borrower's outstanding shares or
    alter or amend Borrower's capital structure.

    LOANS, Acquisitions and Guaranties. (a) Loan, invest in or advance money or
    assets, (b) purchase, create or acquire any interest in any other enterprise
    or entity, or (c) incur any obligation as surety or guarantor other than in
    the ordinary course of business.

CESSATION OF ADVANCES. If Lender has made any commitment to make any Loan to
Borrower, whether under this Agreement or under any other agreement, Lender
shall have no obligation to make Loan Advances or to disburse Loan proceeds if:
(a) Borrower or any Guarantor is in default under the terms of this Agreement or
any of the Related Documents or any other agreement that Borrower or any
Guarantor has with Lender; (b) Borrower or any Guarantor becomes insolvent,
files a petition in bankruptcy or similar proceedings, or is adjudged a
bankrupt; (c) there occurs a material adverse change in Borrower's financial
condition, in the financial condition of any Guarantor, or in the value of any
Collateral securing any Loan; (d) any Guarantor seeks, claims or otherwise
attempts to limit, modify or revoke such Guarantor's guaranty of the Loan or any
other loan with Lender; or (e) Lender in good faith deems itself insecure, even
though no Event of Default shall have occurred.

FINANCIAL COVENANTS.

1. ANNUALLY AUDITED FINANCIAL STATEMENTS WITHIN 90 DAYS OF FISCAL YEAR END. 2.
QUARTERLY INTERNAL FINANCIAL STATEMENTS WITHIN 45 DAYS OF EACH PERIOD.

3. BORROWER TO PROVIDE MONTHLY INVOICES, OPERATING BUDGET AND CAPITAL PURCHASES
BUDGET WITHIN 30 DAYS OF EACH PERIOD.

4. BORROWER TO PROVIDE BANK WITH ANY PERTINENT REVISIONS TO DOW CHEMICAL
COLLABORATION AND LICENSE AGREEMENT.

5. BORROWER TO MAINTAIN CERTIFICATE OF DEPOSIT #2132399 AS PROVIDED FOR IN THE
ASSIGNMENT OF DEPOSIT ACCOUNT AND THE CREDIT APPROVAL REPORT ATTACHED THERETO.

DISBURSEMENT OF FUNDS. DISBURSEMENT OF FUNDS WITH WRITTEN REQUEST BY AUTHORIZED
SIGNERS AND PRESENTATION OF INVOICES SUPPORTING THE DOLLAR AMOUNT OF THE
REQUEST. DISBURSEMENTS WILL BE PAID TO VENDORS DIRECTLY.

PAYMENT TERMS.

BORROWER WILL PAY THIS LOAN IN ACCORDANCE WITH THE FOLLOWING PAYMENT SCHEDULE:
INTEREST ONLY PAYMENTS WILL BE REQUIRED MONTHLY BEGINNING JANUARY 1, 1999. THERE
IS TO BE FOUR ADVANCE PERIODS DURING THE TERM OF THIS NOTE. THE FIRST BEGINNING
ON THIS DATE AND ENDING FEBRUARY 28, 1999. THE SECOND BEGINNING MARCH 1, 1999
AND ENDING MAY 31, 1999. THE THIRD BEGINNING JUNE 1, 1999 AND ENDING AUGUST 31,
1999. THE FOURTH AND FINAL ADVANCE PERIOD BEGINNING SEPTEMBER 1, 1999 AND ENDING
NOVEMBER 30,1999. THE OUTSTANDING BALANCE ON THE LAST DAY OF EACH ADVANCE PERIOD
WILL BE PAID IN FULL BY A NEW NOTE ADVANCE FROM A SEPARATE TERM LOAN TO BE
PROVIDED BY SIERRAWEST BANK THAT WILL AMORTIZE SAID PRINCIPAL BALANCE IN FULL BY
OCTOBER 1, 2001.

HAZARDOUS SUBSTANCES. The terms "hazardous waste hazardous substance,"
"disposal", "release," and "threatened release," as used in this Agreement,
shall have the same meanings as set forth in the "CERCLA," "SARA," the Hazardous
Materials Transportation Act, 40 U.S.C. Section 1801, et seq., the Resource
Conservation and Recovery Act, 42 U.S.C. Section 6901, et seq., Chapters 6.5
through 7.7 of Division 20 of the California Health and Safety Code, Section
25100, et seq., or other applicable state or Federal laws, rules, or regulations
adopted pursuant to any of the foregoing. Except as disclosed to and
acknowledged by Lender in writing, Borrower represents and warrants that : (a)
During the period of Borrower's ownership of the properties, there has been no
unauthorized use, generation, manufacture, storage, treatment, disposal, release
or threatened release of any hazardous waste or substance by any person on,
under, about or from any of the properties. (b) Borrower has no knowledge of, or
reason to believe that there has been (i) an unauthorized use, generation,
manufacture, storage, treatment, disposal, release, or threatened release of any
hazardous waste or substance on, under, about or from the properties by any
prior owners or occupants of any of the properties, or (ii) any actual or
threatened litigation or claims of any kind by any person relating to such
matters. (c) Neither Borrower nor any tenant, contractor, agent or other
authorized user of any of the properties shall, in an unauthorized manner, use,
generate, manufacture, store, treat, dispose of, or release any hazardous waste
or substance on, under, about or from any of the properties; and any such
activity shall be conducted in compliance with all applicable federal, state,
and local laws, regulations, and ordinances, including without limitation those
laws, regulations and ordinances described above. As allowed by applicable law
and upon reasonable prior notice lender may enter upon the premises of Borrower
to inspect the properties for compliance with this section of the agreement. Any
inspections or test made by Lender shall be at Borrower's expense and for
Lender's purposes only and shall not be construed to create any responsibility
or liability on the part of Lender to Borrower or to any other person. The
representations and warranties contained herein are based on Borrower's due
diligence in investigating the properties for hazardous waste and hazardous
substances. Borrower hereby (a) releases and waives any future claims against
Lender for indemnity or contribution in the event Borrower becomes liable for
cleanup or other costs under any such laws, and (b)

<PAGE>   5

11-30-1998                   BUSINESS LOAN AGREEMENT
LOAN NO. 3400069949               (Continued)                             PAGE 5
--------------------------------------------------------------------------------

agrees to indemnify and hold harmless Lender against any and all claims, losses,
liabilities, damages, penalties, and expenses which Lender may directly or
indirectly sustain or suffer resulting from a breach of this section of the
Agreement or as a consequence of any unauthorized use, generation, manufacture,
storage, disposal, release or threatened release of a hazardous waste or
substance on the properties. The provisions of this section of the Agreement,
including the obligation to indemnify, shall survive the payment of the
indebtedness and the termination or expiration of this Agreement and shall not
be affected by Lender's acquisition of any interest in any of the properties,
whether by foreclosure or otherwise..

RIGHT OF SETOFF. Borrower grants to Lender a contractual security interest in,
and hereby assigns, conveys, delivers, pledges, and transfers to Lender all
Borrower's right, title and interest in and to, Borrower's accounts with Lender
(whether checking, savings, or some other account), including without limitation
all accounts held jointly with someone else and all accounts Borrower may open
in the future, excluding however all IRA and Keogh accounts, and all trust
accounts for which the grant of a security interest would be prohibited by law.
Borrower authorizes Lender, to the extent permitted by applicable law, to charge
or setoff all sums owing on the Indebtedness against any and all such accounts.

EVENTS OF DEFAULT. Each of the following shall constitute an Event of Default
under this Agreement:

    DEFAULT ON INDEBTEDNESS. Failure of Borrower to make any payment when due on
    the Loans.

    OTHER DEFAULTS. Failure of Borrower or any Grantor to comply with or to
    perform when due any other term, obligation, covenant or condition contained
    in this Agreement or in any of the Related Documents, or failure of Borrower
    to comply with or to perform any other term, obligation, covenant or
    condition contained in any other agreement between Lender and Borrower.

    ENVIRONMENTAL DEFAULT. Failure of any party to comply with or perform when
    due any term, obligation, covenant or condition contained in any
    environmental agreement executed in connection with any Loan.

    DEFAULT IN FAVOR OF THIRD PARTIES. Should Borrower or any Grantor default
    under any loan, extension of credit, security agreement, purchase or sales
    agreement, or any other agreement, in favor of any other creditor or person
    that may materially affect any of Borrower's property or Borrower's or any
    Grantor's ability to repay the Loans or perform their respective obligations
    under this Agreement or any of the Related Documents.

    FALSE STATEMENTS. Any warranty, representation or statement made or
    furnished to Lender by or on behalf of Borrower or any Grantor under this
    Agreement or the Related Documents is false or misleading in any material
    respect at the time made or furnished, or becomes false or misleading at any
    time thereafter.

    DEFECTIVE COLLATERALIZATION. This Agreement or any of the Related Documents
    ceases to be in full force and effect (including failure of any Security
    Agreement to create a valid and perfected Security Interest) at any time and
    for any reason.

    INSOLVENCY. The dissolution or termination of Borrower's existence as a
    going business, the insolvency of Borrower, the appointment of a receiver
    for any part of Borrower's property, any assignment for the benefit of
    creditors, any type of creditor workout, or the commencement of any
    proceeding under any bankruptcy or insolvency laws by or against Borrower.

    CREDITOR OR FORFEITURE PROCEEDINGS. Commencement of foreclosure or
    forfeiture proceedings, whether by judicial proceeding, self-help,
    repossession or any other method, by any creditor of Borrower, any creditor
    of any Grantor against any collateral securing the Indebtedness, or by any
    governmental agency. This includes a garnishment, attachment, or levy on or
    of any of Borrower's deposit accounts with Lender. However, this Event of
    Default shall not apply if there is a good faith dispute by Borrower or
    Grantor, as the case may be, as to the validity or reasonableness of the
    claim which is the basis of the creditor or forfeiture proceeding, and if
    Borrower or Grantor gives Lender written notice of the creditor or
    forfeiture proceeding and furnishes reserves or a surety bond for the
    creditor or forfeiture proceeding satisfactory to Lender.

    EVENTS AFFECTING GUARANTOR. Any of the preceding events occurs with respect
    to any Guarantor of any of the Indebtedness or any Guarantor dies or becomes
    incompetent, or revokes or disputes the validity of, or liability under, any
    Guaranty of the Indebtedness. Lender, at its option, may, but shall not be
    required to, permit the Guarantor's estate to assume unconditionally the
    obligations arising under the guaranty in a manner satisfactory to Lender,
    and, in doing so, cure the Event of Default.

    CHANGE IN OWNERSHIP. Any change in ownership of twenty-five percent (25%) or
    more of the common stock of Borrower.

    ADVERSE CHANGE. A material adverse change occurs in Borrower's financial
    condition, or Lender believes the prospect of payment or performance of the
    Indebtedness is impaired.

    INSECURITY. Lender, in good faith, deems itself insecure.

    RIGHT TO CURE. If any default, other than a Default on Indebtedness, is
    curable and if Borrower or Grantor, as the case may be, has not been given a
    notice of a similar default within the preceding twelve (12) months, it may
    be cured (and no Event of Default will have occurred) if Borrower or
    Grantor, as the case may be, after receiving written notice from Lender
    demanding cure of such default: (a) cures the default within fifteen (15)
    days; or (b) if the cure requires more than fifteen (15) days, immediately
    initiates steps which Lender deems in Lender's sole discretion to be
    sufficient to cure the default and thereafter continues and completes all
    reasonable and necessary steps sufficient to produce compliance as soon as
    reasonably practical.

EFFECT OF AN EVENT OF DEFAULT. If any Event of Default shall occur, except where
otherwise provided in this Agreement or the Related Documents, all commitments
and obligations of Lender under this Agreement or the Related Documents or any
other agreement immediately will terminate (including any obligation to make
Loan Advances or disbursements), and, at Lender's option, all Indebtedness
immediately will become due and payable, all without notice of any kind to
Borrower, except that in the case of an Event of Default of the type described
in the "Insolvency" subsection above, such acceleration shall be automatic and
not optional. In addition, Lender shall have all the rights and remedies
provided in the Related Documents or available at law, in equity, or otherwise.
Except as may be prohibited by applicable law, all of Lender's rights and
remedies shall be cumulative and may be exercised singularly or concurrently.
Election by Lender to pursue any remedy shall not exclude pursuit of any other
remedy, and an election to make expenditures or to take action to perform an
obligation of Borrower or of any Grantor shall not affect Lender's right to
declare a default and to exercise its rights and remedies.

MISCELLANEOUS PROVISIONS. The following miscellaneous provisions are a part of
this Agreement:

    AMENDMENTS. This Agreement, together with any Related Documents, constitutes
    the entire understanding and agreement of the parties as to the matters set
    forth in this Agreement. No alteration of or amendment to this Agreement
    shall be effective unless given in writing and signed by the party or
    parties sought to be charged or bound by the alteration or amendment.

<PAGE>   6

11-30-1998                   BUSINESS LOAN AGREEMENT
LOAN NO. 3400069949               (Continued)                             PAGE 6
--------------------------------------------------------------------------------

    APPLICABLE LAW. This Agreement has been delivered to Lender and accepted by
    Lender In the State of California. If there Is a lawsuit, Borrower agrees
    upon Lender's request to submit to the jurisdiction of the courts of NEVADA
    County, the State of California. This Agreement shall be governed by and
    construed In accordance with the laws of the State of California.

    CAPTION HEADINGS. Caption headings in this Agreement are for convenience
    purposes only and are not to be used to interpret or define the provisions
    of this Agreement.

    MULTIPLE PARTIES; CORPORATE AUTHORITY. All obligations of Borrower under
    this Agreement shall be joint and several, and all references to Borrower
    shall mean each and every Borrower. This means that each of the persons
    signing below is responsible for all obligations in this Agreement.

    CONSENT TO LOAN PARTICIPATION. Borrower agrees and consents to Lender's sale
    or transfer, whether now or later, of one or more participation interests in
    the Loans to one or more purchasers, whether related or unrelated to Lender.
    Lender may provide, without any limitation whatsoever, to any one or more
    purchasers, or potential purchasers, any information or knowledge Lender may
    have about Borrower or about any other matter relating to the Loan, and
    Borrower hereby waives any rights to privacy it may have with respect to
    such matters. Borrower additionally waives any and all notices of sale of
    participation interests, as well as all notices of any repurchase of such
    participation interests. Borrower also agrees that the purchasers of any
    such participation interests will be considered as the absolute owners of
    such interests in the Loans and will have all the rights granted under the
    participation agreement or agreements governing the sale of such
    participation interests. Borrower further waives all rights of offset or
    counterclaim that it may have now or later against Lender or against any
    purchaser of such a participation interest and unconditionally agrees that
    either Lender or such purchaser may enforce Borrower's obligation under the
    Loans irrespective of the failure or insolvency of any holder of any
    interest in the Loans. Borrower further agrees that the purchaser of any
    such participation interests may enforce its interests irrespective of any
    personal claims or defenses that Borrower may have against Lender.

    COSTS AND EXPENSES. Borrower agrees to pay upon demand all of Lender's
    expenses, including without limitation attorneys' fees, incurred in
    connection with the preparation, execution, enforcement, modification and
    collection of this Agreement or in connection with the Loans made pursuant
    to this Agreement. Lender may pay someone else to help collect the Loans and
    to enforce this Agreement, and Borrower will pay that amount. This includes,
    subject to any limits under applicable law, Lender's attorneys' fees and
    Lender's legal expenses, whether or not there is a lawsuit, including
    attorneys' fees for bankruptcy proceedings (including efforts to modify or
    vacate any automatic stay or injunction), appeals, and any anticipated
    post-judgment collection services. Borrower also will pay any court costs,
    in addition to all other sums provided by law.

    NOTICES. All notices required to be given under this Agreement shall be
    given in writing, may be sent by telefacsimile (unless otherwise required by
    law), and shall be effective when actually delivered or when deposited with
    a nationally recognized overnight courier or deposited in the United States
    mail, first class, postage prepaid, addressed to the party to whom the
    notice is to be given at the address shown above. Any party may change its
    address for notices under this Agreement by giving formal written notice to
    the other parties, specifying that the purpose of the notice is to change
    the party's address. To the extent permitted by applicable law, it there is
    more than one Borrower, notice to any Borrower will constitute notice to all
    Borrowers. For notice purposes, Borrower will keep Lender informed at all
    times of Borrower's current address(es).

    SEVERABILITY. If a court of competent jurisdiction finds any provision of
    this Agreement to be invalid or unenforceable as to any person or
    circumstance, such finding shall not render that provision invalid or
    unenforceable as to any other persons or circumstances. If feasible, any
    such offending provision shall be deemed to be modified to be within the
    limits of enforceability or validity; however, if the offending provision
    cannot be so modified, it shall be stricken and all other provisions of this
    Agreement in all other respects shall remain valid and enforceable.

    SUBSIDIARIES AND AFFILIATES OF BORROWER. To the extent the context of any
    provisions of this Agreement makes it appropriate, including without
    limitation any representation, warranty or covenant, the word "Borrower" as
    used herein shall include all subsidiaries and affiliates of Borrower.
    Notwithstanding the foregoing however, under no circumstances shall this
    Agreement be construed to require Lender to make any Loan or other financial
    accommodation to any subsidiary or affiliate of Borrower.

    SUCCESSORS AND ASSIGNS. All covenants and agreements contained by or on
    behalf of Borrower shall bind its successors and assigns and shall inure to
    the benefit of Lender, its successors and assigns. Borrower shall not,
    however, have the right to assign its rights under this Agreement or any
    interest therein, without the prior written consent of Lender.

    SURVIVAL. All warranties, representations, and covenants made by Borrower in
    this Agreement or in any certificate or other instrument delivered by
    Borrower to Lender under this Agreement shall be considered to have been
    relied upon by Lender and will survive the making of the Loan and delivery
    to Lender of the Related Documents, regardless of any investigation made by
    Lender or on Lender's behalf.

    TIME IS OF THE ESSENCE. Time is of the essence in the performance of this
    Agreement.

    WAIVER. Lender shall not be deemed to have waived any rights under this
    Agreement unless such waiver is given in writing and signed by Lender. No
    delay or omission on the part of Lender in exercising any right shall
    operate as a waiver of such right or any other right. A waiver by Lender of
    a provision of this Agreement shall not prejudice or constitute a waiver of
    Lender's right otherwise to demand strict compliance with that provision or
    any other provision of this Agreement. No prior waiver by Lender, nor any
    course of dealing between Lender and Borrower, or between Lender and any
    Grantor, shall constitute a waiver of any of Lender's rights or of any
    obligations of Borrower or of any Grantor as to any future transactions.
    Whenever the consent of Lender is required under this Agreement, the
    granting of such consent by Lender in any instance shall not constitute
    continuing consent in subsequent instances where such consent is required,
    and in all cases such consent may be granted or withheld in the sole
    discretion of Lender.

<PAGE>   7

11-30-1998                   BUSINESS LOAN AGREEMENT
LOAN NO. 3400069949               (Continued)                             PAGE 7
--------------------------------------------------------------------------------

BORROWER ACKNOWLEDGES HAVING READ ALL THE PROVISIONS OF THIS BUSINESS LOAN
AGREEMENT, AND BORROWER AGREES TO ITS TERMS. THIS AGREEMENT IS DATED AS OF
NOVEMBER 30,1998.

BORROWER:

BIOSOURCE TECHNOLOGIES, INC.

By: /s/ Robert L. Erwin                        By: /s/ Michael D. Centron
   --------------------------------------         ------------------------------
   ROBERT L. ERWIN, CHAIRMAN OF THE  BOARD        MICHAEL D. CENTRON, TREASURER

LENDER:

SIERRAWEST BANK

By:
   ------------------------------------
   Authorized Officer

--------------------------------------------------------------------------------

<PAGE>   8

                                 PROMISSORY NOTE
<TABLE>
<CAPTION>
--------------------------------------------------------------------------------------------------------------
    PRINCIPAL        LOAN DATE       MATURITY       LOAN NO     CALL    COLLATERAL  ACCOUNT   OFFICER  INITIALS
<S>                  <C>            <C>           <C>           <C>     <C>         <C>       <C>      <C>
  $5,000,000.00      11-30-1998     11-30-1999    3400069949     10                 111721      274
--------------------------------------------------------------------------------------------------------------
</TABLE>
References in the shaded area are for Lender's use only and do not limit the
applicability of this document to any particular loan or item.
--------------------------------------------------------------------------------

BORROWER:  BIOSOURCE TECHNOLOGIES, INC.           LENDER: SIERRAWEST BANK
           (TIN:  77-0154648)                             CENTRAL PACIFIC REGION
           3333 VACA VALLEY PARKWAY, SUITE 1000           1100 TEXAS ST.
           VACAVILLE, CA  95688-9412                      FAIRFIELD, CA  94533

--------------------------------------------------------------------------------

<TABLE>
<S>                                <C>                     <C>
PRINCIPAL AMOUNT: $5,000,000.00    INITIAL RATE: 7.750%    DATE OF NOTE: NOVEMBER 30, 1998
</TABLE>

PROMISE TO PAY. BIOSOURCE TECHNOLOGIES, INC. ("Borrower") promises to pay to
SierraWest Bank ("Lender"), or order, In lawful money of the United States of
America, the principal amount of Five Million & 00/100 Dollars ($5,000,000.00)
or so much as may be outstanding, together with Interest on the unpaid
outstanding principal balance of each advance. Interest shall be calculated from
the date of each advance until repayment of each advance.

PAYMENT. Borrower will pay this loan in accordance with the following payment
schedule:

        BORROWER WILL PAY THIS LOAN IN ACCORDANCE WITH THE FOLLOWING PAYMENT
        SCHEDULE; INTEREST ONLY PAYMENTS WILL BE REQUIRED MONTHLY BEGINNING
        JANUARY 1, 1999. THERE IS TO BE FOUR ADVANCE PERIODS DURING THE TERM OF
        THIS NOTE. THE FIRST BEGINNING ON THIS DATE AND ENDING FEBRUARY 28,
        1999. THE SECOND BEGINNING MARCH 1, 1999 AND ENDING MAY 31, 1999. THE
        THIRD BEGINNING JUNE 1, 1999 AND ENDING AUGUST 31,1999. THE FOURTH AND
        FINAL ADVANCE PERIOD BEGINNING SEPTEMBER 1, 1999 AND ENDING NOVEMBER
        30,1999. THE OUTSTANDING BALANCE ON THE LAST DAY OF EACH ADVANCE PERIOD
        WILL BE PAID IN FULL BY A NEW NOTE ADVANCE FROM A SEPARATE TERM LOAN TO
        BE PROVIDED BY SIERRAWEST BANK THAT WILL AMORTIZE SAID PRINCIPAL BALANCE
        IN FULL BY OCTOBER 1, 2001

The annual interest rate for this Note is computed on a 365/360 basis; that is,
by applying the ratio of the annual interest rate over a year of 360 days,
multiplied by the outstanding principal balance, multiplied by the actual number
of days the principal balance is outstanding. Borrower will pay Lender at
Lender's address shown above or at such other place as Lender may designate in
writing. Unless otherwise agreed or required by applicable law, payments will be
applied first to accrued unpaid interest, then to principal, and any remaining
amount to any unpaid collection costs and late charges.

VARIABLE INTEREST RATE. The interest rate on this Note is subject to change from
time to time based on changes in an independent index which is the Prime rate as
published in the western edition of the Wall Street Journal (the "Index"). The
Index is not necessarily the lowest rate charged by Lender on its loans. If the
Index becomes unavailable during the term of this loan, Lender may designate a
substitute index after notice to Borrower. Lender will tell Borrower the current
Index rate upon Borrower's request. Borrower understands that Lender may make
loans based on other rates as well. The interest rate change will not occur more
often than each day. The Index currently Is 7.750%. The Interest rate to be
applied to the unpaid principal balance of this Note will be at a rate equal to
the Index, resulting In an Initial rate of 7.760%. NOTICE: Under no
circumstances will the interest rate on this Note be more than the maximum rate
allowed by applicable law.

PREPAYMENT. Borrower agrees that all loan fees and other prepaid finance charges
are earned fully as of the date of the loan and will not be subject to refund
upon early payment (whether voluntary or as a result of default), except as
otherwise required by law. Except for the foregoing, Borrower may pay without
penalty all or a portion of the amount owed earlier than it is due. Early
payments will not, unless agreed to by Lender in writing, relieve Borrower of
Borrower's obligation to continue to make payments of accrued unpaid interest.
Rather, they will reduce the principal balance due.

LATE CHARGE. If a payment is 10 days or more late, Borrower will be charged
5.000% of the regularly scheduled payment or $15.00, whichever is greater.

DEFAULT. Borrower will be in default if any of the following happens: (a)
Borrower fails to make any payment when due. (b) Borrower breaks any contained
in this Note or any agreement related to this Note, or in any other agreement or
loan Borrower has with Lender. (c) Borrower defaults under any loan, extension
of credit, security agreement, purchase or sales agreement, or any other
agreement, in favor of any other creditor or person that may materially affect
any of Borrower's property or Borrower's ability to repay this Note or perform
Borrower's obligations under this Note or any of the Related Documents. (d) Any
representation or statement made or furnished to Lender by Borrower or on
Borrower's behalf is false or misleading in any material respect either now or
at the time made or furnished. (e) Borrower becomes insolvent, a receiver is
appointed for any part of Borrower's property, Borrower makes an assignment for
the benefit of creditors, or any proceeding is commenced either by Borrower or
against Borrower under any bankruptcy or insolvency laws. (f) Any creditor tries
to take any of Borrower's property on or in which Lender has a lien or security
interest. This includes a garnishment of any of Borrower's accounts with Lender.
(g) Any guarantor dies or any of the other events described in this default
section occurs with respect to any guarantor of this Note. (h) A material
adverse change occurs in Borrower's financial condition, or Lender believes the
prospect of payment or performance of the Indebtedness is impaired. (i) Lender
in good faith deems itself insecure.

If any default, other than a default in payment, is curable and if Borrower has
not been given a notice of a breach of the same provision of this Note within
the preceding twelve (12) months, it may be cured (and no event of default will
have occurred) if Borrower, after receiving written notice from Lender demanding
cure of such default: (a) cures the default within fifteen (15) days; or (b) if
the cure requires more than fifteen (15) days, immediately initiates steps which
Lender deems in Lender's sole discretion to be sufficient to cure the default
and thereafter continues and completes all reasonable and necessary steps
sufficient to produce compliance as soon as reasonably practical.

LENDER'S RIGHTS. Upon default, Lender may declare the entire unpaid principal
balance on this Note and all accrued unpaid interest immediately due, without
notice, and then Borrower will pay that amount. Upon Borrower's failure to pay
all amounts declared due pursuant to this section, including failure to pay upon
final maturity, Lender, at its option, may also, if permitted under applicable
law, increase the variable interest rate on this Note to 5.000 percentage points
over the Index. Lender may hire or pay someone else to help collect this Note if
Borrower does not pay. Borrower also will pay Lender that amount. This includes,
subject to any limits under applicable law, Lender's attorneys' fees and
Lender's legal expenses whether or not there is a lawsuit, including attorneys'
fees and legal expenses for bankruptcy proceedings (including efforts to modify
or vacate any automatic stay or injunction), appeals, and any anticipated
post-judgment collection services. Borrower also will pay any court costs, in
addition to all other sums provided

<PAGE>   9

11-30-1998                      PROMISSORY NOTE
LOAN NO. 3400069949               (CONTINUED)                             PAGE 2
--------------------------------------------------------------------------------

by law. This Note has been delivered to Lender and accepted by Lender In the
State of California. If there Is a lawsuit, Borrower agrees upon Lender's
request to submit to the jurisdiction of the courts of NEVADA County, the State
of California. This Note shall be governed by and construed in accordance with
the laws of the State of California.

RIGHT OF SETOFF. Borrower grants to Lender a contractual security interest in,
and hereby assigns, conveys, delivers, pledges, and transfers to Lender all
Borrower's right, title and interest in and to, Borrower's accounts with Lender
(whether checking, savings, or some other account), including without limitation
all accounts hold jointly with someone else and all accounts Borrower may open
in the future, excluding however all IRA and Keogh accounts, and all trust
accounts for which the grant of a security interest would be prohibited by law.
Borrower authorizes Lender, to the extent permitted by applicable law, to charge
or setoff all sums owing on this Note against any and all such accounts.

LINE OF CREDIT. This Note evidences a straight line of credit. Once the total
amount of principal has been advanced, Borrower is not entitled to further loan
advances. Advances under this Note may be requested orally by Borrower or by an
authorized person. All oral requests shall be confirmed in writing on the day of
the request. All communications, instructions, or directions by telephone or
otherwise to Lender are to be directed to Lender's office shown above. The
following party or parties are authorized to request advances under the line of
credit until Lender receives from Borrower at Lender's address shown above
written notice of revocation of their authority: ROBERT L. ERWIN, PRESIDENT;
MICHAEL D. CENTRON, TREASURER; and JOHN S. RAKITAN, SECRETARY. Borrower agrees
to be liable for all sums either: (a) advanced in accordance with the
instructions of an authorized person or (b) credited to any of Borrower's
accounts with Lender. The unpaid principal balance owing on this Note at any
time may be evidenced by endorsements on this Note or by Lender's internal
records, including daily computer print-outs. Lender will have no obligation to
advance funds under this Note if: (a) Borrower or any guarantor is in default
under the terms of this Note or any agreement that Borrower or any guarantor has
with Lender, including any agreement made in connection with the signing of this
Note; (b) Borrower or any guarantor ceases doing business or is insolvent; (c)
any guarantor seeks, claims or otherwise attempts to limit, modify or revoke
such guarantor's guarantee of this Note or any other loan with Lender; (d)
Borrower has applied funds provided pursuant to this Note for purposes other
than those authorized by Lender; or (e) Lender in good faith deems itself
insecure under this Note or any other agreement between Lender and Borrower.

DISBURSEMENT OF FUNDS. DISBURSEMENT OF FUNDS WITH WRITTEN REQUEST BY AUTHORIZED
SIGNERS AND PRESENTATION OF INVOICES SUPPORTING THE DOLLAR AMOUNT OF THE
REQUEST. DISBURSEMENTS WILL BE PAID TO VENDORS DIRECTLY.

GENERAL PROVISIONS. Lender may delay or forgo enforcing any of its rights or
remedies under this Note without losing them. Borrower and any other person who
signs, guarantees or endorses this Note, to the extent allowed by law, waive any
applicable statute of limitations, presentment, demand for payment, protest and
notice of dishonor. Upon any change in the terms of this Note, and unless
otherwise expressly stated in writing, no party who signs this Note, whether as
maker, guarantor, accommodation maker or endorser, shall be released from
liability. All such parties agree that Lender may renew or extend (repeatedly
and for any length of time) this loan, or release any party or guarantor or
collateral; or impair, fail to realize upon or perfect Lender's security
interest in the collateral; and take any other action deemed necessary by Lender
without the consent of or notice to anyone. All such parties also agree that
Lender may modify this loan without the consent of or notice to anyone other
than the party with whom the modification is made.

PRIOR TO SIGNING THIS NOTE, BORROWER READ AND UNDERSTOOD ALL THE PROVISIONS OF
THIS NOTE, INCLUDING THE VARIABLE INTEREST RATE PROVISIONS. BORROWER AGREES TO
THE TERMS OF THE NOTE AND ACKNOWLEDGES RECEIPT OF A COMPLETED COPY OF THE NOTE.

BORROWER:

BIOSOURCE TECHNOLOGIES, INC.

By: /s/ Robert L. Erwin                     By: /s/  Michael D. Centron
   -------------------------------------       ---------------------------------
   ROBERT L. ERWIN, CHAIRMAN OF THE  BOARD     MICHAEL D. CENTRON, TREASURER

--------------------------------------------------------------------------------

<PAGE>   10

                         CORPORATE RESOLUTION TO BORROW

<TABLE>
<CAPTION>
--------------------------------------------------------------------------------------------------------------
    PRINCIPAL        LOAN DATE       MATURITY       LOAN NO     CALL    COLLATERAL  ACCOUNT   OFFICER  INITIALS
<S>                  <C>            <C>           <C>           <C>     <C>         <C>       <C>      <C>
  $5,000,000.00      11-30-1998     11-30-1999    3400069949     10                 111721      274
--------------------------------------------------------------------------------------------------------------
</TABLE>

References in the shaded area are for Lender's use only and do not limit the
applicability of this document to any particular loan or item.

--------------------------------------------------------------------------------

BORROWER: BIOSOURCE TECHNOLOGIES, INC.          LENDER:  SIERRAWEST BANK
          (TIN:  77-0154648)                             CENTRAL PACIFIC REGION
          3333 VACA VALLEY PARKWAY, SUITE 1000           1100 TEXAS ST.
          VACAVILLE, CA  95688-9412                      FAIRFIELD, CA  94533
--------------------------------------------------------------------------------

I, the undersigned Secretary or Assistant Secretary of BIOSOURCE TECHNOLOGIES,
INC. (the "Corporation"), HEREBY CERTIFY that the Corporation is organized and
existing under and by virtue of the laws of the State of California as a
corporation for profit, with its principal office at 3333 VACA VALLEY PARKWAY,
SUITE 1000, VACAVILLE, CA 95688-9412, and is duly authorized to transact
business in the State of California.

I FURTHER CERTIFY that at a meeting of the Directors of the Corporation, duly
called and held on , at which a quorum was present and voting, or by other duly
authorized corporate action in lieu of a meeting, the following resolutions were
adopted:

BE IT RESOLVED, that any two (2) of the following named officers, employees, or
agents of this Corporation, whose actual signatures are shown below:

<TABLE>
<CAPTION>
          NAMES                           POSITIONS                      ACTUAL SIGNATURES
          -----                           ---------                      -----------------
<S>                                  <C>                                 <C>
    Robert L. Erwin                  Chairman of the Board               Robert L. Erwin

    Michael D. Centron               Treasurer                           Michael D. Centron

    John S. Rakitan                  Secretary                           John S. Rakitan
</TABLE>

acting for and on behalf of the Corporation and as its act and deed be, and they
hereby are, authorized and empowered:

    BORROW MONEY. To borrow from time to time from SierraWest Bank ("Lender"),
    on such terms as may be agreed upon between the Corporation and Lender, such
    sum or sums of money as in their judgment should be borrowed; however, not
    exceeding at any one time the principal amount of Five Million & 00/100
    Dollars ($5,000,000.00), in addition to such sum or sums of money as may be
    currently borrowed by the Corporation from Lender.

    EXECUTE NOTES. To execute and deliver to Lender the promissory note or
    notes, or other evidence of credit accommodations of the Corporation, on
    Lender's forms, at such rates of interest and on such terms as may be agreed
    upon, evidencing the sums of money so borrowed or any indebtedness of the
    Corporation to Lender, and also to execute and deliver to Lender one or more
    renewals, extensions, modifications, refinancings, consolidations, or
    substitutions for one or more of the notes, any portion of the notes, or any
    other evidence of credit accommodations.

    GRANT SECURITY. To mortgage, pledge, transfer, endorse, hypothecate, or
    otherwise encumber and deliver to Lender, as security for the payment of any
    loans or credit accommodations so obtained, any promissory notes so executed
    (including any amendments to or modifications, renewals, and extensions of
    such promissory notes), or any other or further indebtedness of the
    Corporation to Lender at any time owing, however the same may be evidenced,
    any property now or hereafter belonging to the Corporation or in which the
    Corporation now or hereafter may have an interest, including without
    limitation all real property and all personal property (tangible or
    intangible) of the Corporation. Such property may be mortgaged, pledged,
    transferred, endorsed, hypothecated, or encumbered at the time such loans
    are obtained or such indebtedness is incurred, or at any other time or
    times, and may be either in addition to or in lieu of any property
    theretofore mortgaged, pledged, transferred, endorsed, hypothecated, or
    encumbered.

    EXECUTE SECURITY DOCUMENTS. To execute and deliver to Lender the forms of
    mortgage, deed of trust, pledge agreement, hypothecation agreement, and
    other security agreements and financing statements which may be required by
    Lender and which shall evidence the terms and conditions under and pursuant
    to which such liens and encumbrances, or any of them, are given; and also to
    execute and deliver to Lender any other written instruments, any chattel
    paper, or any other collateral, of any kind or nature, which Lender may deem
    necessary or proper in connection with or pertaining to the giving of the
    liens and encumbrances. Notwithstanding the foregoing, any one of the above
    authorized persons may execute, deliver, or record financing statements.

    NEGOTIATE ITEMS. To draw, endorse, and discount with Lender all drafts,
    trade acceptances, promissory notes, or other evidences of indebtedness
    payable to or belonging to the Corporation in which the Corporation may have
    an interest, and either to receive cash for the same or to cause such
    proceeds to be credited to the account of the Corporation with Lender, or to
    cause such other disposition of the proceeds derived therefrom as they may
    deem advisable.

    FURTHER ACTS. In the case of lines of credit, to designate additional or
    alternate individuals as being authorized to request advances thereunder,
    and in all cases, to do and perform such other acts and things, to pay any
    and all fees and costs, and to execute and deliver such other documents and
    agreements as they may in their discretion deem reasonably necessary or
    proper in order to carry into effect the provisions of these Resolutions.
    The following person or persons currently are authorized to request advances
    and authorize payments under the line of credit until Lender receives
    written notice of revocation of their authority: ROBERT L. ERWIN, PRESIDENT;
    MICHAEL D. CENTRON, TREASURER; and JOHN S. RAKITAN, SECRETARY.

BE IT FURTHER RESOLVED, that any and all acts authorized pursuant to these
Resolutions and performed prior to the passage of these Resolutions are hereby
ratified and approved, that these Resolutions shall remain in full force and
effect and Lender may rely on these Resolutions until written notice of their
revocation shall have been delivered to and received by Lender. Any such notice
shall not affect any of the Corporation's agreements or commitments in effect at
the time notice is given.

BE IT FURTHER RESOLVED, that the Corporation will notify Lender in writing at
Lender's address shown above (or such other addresses as Lender may designate
from time to time) prior to any (a) change in the name of the Corporation, (b)
change in the assumed business name(s) of the

<PAGE>   11

Corporation, (c) change in the management of the Corporation,, (d) change in the
authorized signer(s), (e) conversion of the Corporation to a new or
different type of business entity, or (f) change in any other aspect of the
Corporation that directly or indirectly relates to any agreements between the
Corporation and Lender. No change in the name of the Corporation will take
effect until after Lender has been notified.

I FURTHER CERTIFY that the officers, employees, and agents named above are duly
elected, appointed, or employed by or for the Corporation, as the case may be,
and occupy the positions set opposite their respective names; that the foregoing
Resolutions now stand of record on the books of the Corporation; and that the
Resolutions are in full force and effect and have not been modified or revoked
in any manner whatsoever. The Corporation has no corporate seal, and therefore,
no seal is affixed to this certificate.

IN TESTIMONY WHEREOF, I have hereunto set my hand on November 30, 1998 and
attest that the signatures set opposite the names listed above are their genuine
signatures.

                                        CERTIFIED TO AND ATTESTED BY:

                                        John S. Ratikan
                                        ----------------------------------------

                                        x
                                        ----------------------------------------

NOTE: In case the Secretary or other certifying officer is designated by the
foregoing resolutions as one of the signing officers, it is advisable to have
this certificate signed by a second Officer or Director of the Corporation.

<PAGE>   12

                     DISBURSEMENT REQUEST AND AUTHORIZATION

<TABLE>
<CAPTION>
--------------------------------------------------------------------------------------------------------------
    PRINCIPAL        LOAN DATE       MATURITY       LOAN NO     CALL    COLLATERAL  ACCOUNT   OFFICER  INITIALS
<S>                  <C>            <C>           <C>           <C>     <C>         <C>       <C>      <C>
  $5,000,000.00      11-30-1998     11-30-1999    3400069949     10                 111721      274
--------------------------------------------------------------------------------------------------------------
</TABLE>

References in the shaded area are for Lender's use only and do not limit the
applicability of this document to any particular loan or item.
--------------------------------------------------------------------------------

BORROWER: BIOSOURCE TECHNOLOGIES, INC.           LENDER:  SIERRAWEST BANK
          (TIN:  77-0154648)                              CENTRAL PACIFIC REGION
          3333 VACA VALLEY PARKWAY, SUITE 1000            1100 TEXAS ST.
          VACAVILLE, CA  95688-9412                       FAIRFIELD, CA  94533
--------------------------------------------------------------------------------

LOAN TYPE. This is a Variable Rate (at Prime rate as published in the western
edition of the Wall Street Journal, making an initial rate of 7.750%),
Non-Revolving Line of Credit Loan to a Corporation for $5,000,000.00 due on
November 30, 1999.

PRIMARY PURPOSE OF LOAN. The primary purpose of this loan is for:

        [ ]    Personal, Family, or Household Purposes or Personal Investment.

        [X]    Business (including Real Estate Investment).

SPECIFIC PURPOSE. The specific purpose of this loan is: BUSINESS NON-REVOLVING
LINE OF CREDIT.

DISBURSEMENT INSTRUCTIONS. Borrower understands that no loan proceeds will be
disbursed until all of Lender's conditions for making the loan have been
satisfied. Please disburse the loan proceeds of $5,000,000.00 as follows:

<TABLE>
<S>                                                                 <C>
        Undisbursed Funds:                                          $4,975,000.00
        Total Financed Prepaid Finance Charges:                        $25,000.00
            $25,000.00 Points                                       -------------
        Note Principal:                                             $5,000,000.00
</TABLE>

FINANCIAL CONDITION. BY SIGNING THIS AUTHORIZATION, BORROWER REPRESENTS AND
WARRANTS TO LENDER THAT THE INFORMATION PROVIDED ABOVE IS TRUE AND CORRECT AND
THAT THERE HAS BEEN NO MATERIAL ADVERSE CHANGE IN BORROWER'S FINANCIAL CONDITION
AS DISCLOSED IN BORROWER'S MOST RECENT FINANCIAL STATEMENT TO LENDER. THIS
AUTHORIZATION IS DATED NOVEMBER 30,1998.

BORROWER:

BIOSOURCE TECHNOLOGIES, INC.

By: /s/ Robert L. Erwin                        By: /s/ Michael D. Centron
   -------------------------------------          ------------------------------
   ROBERT L. ERWIN, CHAIRMAN OF THE  BOARD        MICHAEL D. CENTRON, TREASURER

--------------------------------------------------------------------------------

<PAGE>   13

--------------------------------------------------------------------------------
                         AGREEMENT TO PROVIDE INSURANCE
<TABLE>
<CAPTION>
--------------------------------------------------------------------------------------------------------------
    PRINCIPAL        LOAN DATE       MATURITY       LOAN NO     CALL    COLLATERAL  ACCOUNT   OFFICER  INITIALS
<S>                  <C>            <C>           <C>           <C>     <C>         <C>       <C>      <C>
  $5,000,000.00      11-30-1998     11-30-1999    3400069949     10                 111721      274
--------------------------------------------------------------------------------------------------------------
</TABLE>

References in the shaded area are for Lender's use only and do not limit the
applicability of this document to any particular loan or item.

--------------------------------------------------------------------------------

BORROWER:  BIOSOURCE TECHNOLOGIES, INC.           LENDER: SIERRAWEST BANK
           (TIN:  77-0154648)                             CENTRAL PACIFIC REGION
           3333 VACA VALLEY PARKWAY, SUITE 1000           1100 TEXAS ST.
           VACAVILLE, CA  95688-9412                      FAIRFIELD, CA  94533
--------------------------------------------------------------------------------

INSURANCE REQUIREMENTS. BIOSOURCE TECHNOLOGIES, INC. ("Grantor") understands
that insurance coverage is required in connection with the extending of a loan
or the providing of other financial accommodations to Grantor by Lender. These
requirements are set forth in the security documents. The following minimum
insurance coverages must be provided on the following described collateral (the
"Collateral"):

<TABLE>
<S>            <C>
COLLATERAL:    ALL EQUIPMENT, CHATTEL PAPER, PERSONAL PROPERTY, ACCOUNTS RECEIVABLE, CONTRACT
               RIGHTS AND INTANGIBLES, NOW OR HEREAFTER ACQUIRED, BUT NOT INCLUDING ANY
               PATENTS, COPY RIGHTS OR TRADEMARKS OR SIMILAR INTELLECTUAL PROPERTY.
               TYPE. All risks, including fire, theft and liability.
               AMOUNT. $5,000,000.00.
               BASIS. Replacement value.
               Endorsements. Lender's loss payable clause with stipulation that coverage will
               not be cancelled or diminished without a minimum of ten (10) days' prior
               written notice to Lender.
               DEDUCTIBLES. $1,000.00.
</TABLE>

INSURANCE COMPANY. Grantor may obtain insurance from any insurance company
Grantor may choose that is reasonably acceptable to Lender. Grantor understands
that credit may not be denied solely because insurance was not purchased through
Lender.

INSURANCE MAILING ADDRESS. All documents and other materials relating to
insurance for this loan should be mailed, delivered or directed to the following
address:

               SierraWest Bank, Attention: S. Powell
               P. 0. Box 61000
               10181 Truckee Tahoe Airport Rd.
               Truckee, CA 96160
               (530) 582-3864

FAILURE TO PROVIDE INSURANCE. Grantor agrees to deliver to Lender, ten (10) days
from the date of this Agreement, evidence of the required insurance as provided
above, with an effective date of November 30, 1998, or earlier.

AUTHORIZATION. For purposes of insurance coverage on the Collateral, Grantor
authorizes Lender to provide to any person (including any insurance agent or
company) all information Lender deems appropriate, whether regarding the
Collateral, the loan or other financial accommodations, or both.

GRANTOR ACKNOWLEDGES HAVING READ ALL THE PROVISIONS OF THIS AGREEMENT TO PROVIDE
INSURANCE AND AGREES TO ITS TERMS. THIS AGREEMENT IS DATED NOVEMBER 30,1998.

GRANTOR:

BIOSOURCE TECHNOLOGIES, INC.

By: /s/ Robert L. Erwin                    By: /s/ Michael D. Centron
   -------------------------------------      ----------------------------------
   ROBERT L. ERWIN, CHAIRMAN OF THE  BOARD    MICHAEL D. CENTRON, TREASURER

--------------------------------------------------------------------------------
                               FOR LENDER USE ONLY
                              INSURANCE VERIFICATION            PHONE:
DATE:
     ---------------------------------------------------------------------------
AGENT'S NAME
             -------------------------------------------------------------------
INSURANCE COMPANY:
                  --------------------------------------------------------------
POLICY NUMBER:
              ------------------------------------------------------------------
EFFECTIVE DATES:
                ----------------------------------------------------------------
COMMENTS:
         -----------------------------------------------------------------------

--------------------------------------------------------------------------------

<PAGE>   14

                               COLLATERAL RECEIPT

<TABLE>
<CAPTION>
--------------------------------------------------------------------------------------------------------------
    PRINCIPAL        LOAN DATE       MATURITY       LOAN NO     CALL    COLLATERAL  ACCOUNT   OFFICER  INITIALS
<S>                  <C>            <C>           <C>           <C>     <C>         <C>       <C>      <C>
  $5,000,000.00      11-30-1998     11-30-1999    3400069949     10                 111721      274
--------------------------------------------------------------------------------------------------------------
</TABLE>

References in the shaded area are for Lender's use only and do not limit the
applicability of this document to any particular loan or item.

--------------------------------------------------------------------------------

BORROWER: BIOSOURCE TECHNOLOGIES, INC.           LENDER: SIERRAWEST BANK
          (TIN:  77-0154648)                             CENTRAL PACIFIC REGION
          3333 VACA VALLEY PARKWAY, SUITE 1000           1100 TEXAS ST.
          VACAVILLE, CA  95688-9412                      FAIRFIELD, CA  94533
--------------------------------------------------------------------------------

<TABLE>
<CAPTION>
------------------------------------- ------------------------------------ ------------------------------------
<S>                                   <C>                                  <C>
     DESCRIPTION OF COLLATERAL            Custody Control Signatures                  Date Released
------------------------------------- ------------------------------------ ------------------------------------

CERTIFICATE OF DEPOSIT #2132399 IN
APPROXIMATE AMOUNT OF $939,300.00
------------------------------------- ------------------------------------ ------------------------------------
</TABLE>

<TABLE>
<S>                                   <C>                                     <C>
----------------------------------    ------------------------------------    --------------------------------
Initial Delivery                      RETURN RECEIPT ACKNOWLEDGEMENT:         INSTRUCTIONS FOR RETURNING
Acknowledgements:                                                             COLLATERAL AND DISPOSITION OF
                                      GRANTOR ACKNOWLEDGES THE RECEIPT        COUPONS:_______________________
Grantor:________________________      OF ALL COLLATERAL, INCLUDING ALL        _______________________________
       (Grantor's Signature)          UNMATURED COUPONS, IF ANY.              _______________________________

SierraWest Bank                       X________________________________
By:_____________________________
       (Authorized Officer)
----------------------------------    ------------------------------------    --------------------------------
</TABLE>

--------------------------------------------------------------------------------

<PAGE>   15

                 ADDENDUM TO CAR DATED 10-15-98, APPROVED BY DLC
                     10-21-98, BIOSOURCE TECHNOLOGIES, INC.

The DLC approved the Biosource Technologies Inc. request Subject to those
conditions set forth in the attached CAR Plus the following:

Biosource Technologies, Inc. is to provide cash collateral in the form of a
Certificate of Deposit, to be renewed quarterly, In an amount equal to 30% of
tile Outstanding projected balance at the end of each quarter. The total
equipment purchase price is estimated at $5,571,201 per the attached schedule.
Inasmuch as there will be a moving target over the term of this loan, and that
$570,201 of the $5,571,201 was already purchased by Biosource through September
30, 1998, the amounts of the required collateral through the remaining term of
the loan is roughly Calculated as follows:

<TABLE>
<S>                  <C>             <C>                     <C>                <C>             <C>
    Oct. `98         Nov. `98        Dec. `98                   Jan. `99        Feb. `99        Mar. `99
        $400,000      $1,905,000      $3,131,000                 $4,154,000      $4,243,861      $4,516,722
Less principal payments:                                             86,139          85,139          85,139
Balance after principle payments:
                                                                  4,068,861       4,158,722       4,431,538
                                      X. 30                                                      X. 30
                                      -----                                                      -----
1st Qtr                                 $939,300             2nd Qtr                             $1,329,461

   April `99         May `99         Jun `99                    Jul `99         Aug `99         Sep `99
      $4,489,538      $4,413,598      $4,317,658                 $4,213,718       4,101,773        ********
         133,940         133,940         133,940                    141,940         141,940         141,940
       4,355,598       4,279,658       4,183,718                  4,071,778       3,959,838       3,817,898
                                      X. 30                                                      X. 30
                                      -----                                                      -----
3rd Qtr                               $1,255,115             4th Qtr                             $1,145,369

    Oct `99          Nov `99         Dec `99                    Jan `00         Feb `00         Mar "00
         *******         *******         *******                    *******         *******         *******
         147,220          14,220          14,220                    150,316         150,316         150,316
       3,670,678       3,523,458       3,367,238                  3,225,922       3,075,606       2,925,290
                                      X .30                                                      X. 30
                                      -----                                                      -----
5th Qtr.                              $1,012,871             6th Qtr.                              $877,587

    Apr `00          May `00         Jun `00                    Jul `00         Aug `00         Sep `00
         *******         *******         *******                    *******         *******         *******
         163,081         163,081         163,081                    166,588         166,588         166,588
       2,762,209       2,599,128       2,436,047                  2,269,459        2,102,71       1,936,283
                                      X. 30                                                      X. 30
                                      -----                                                      -----
7th Qtr                                 $730,814             8th Qtr                               $580,885

    Oct `00          Nov `00         Dec `00                    Jan `01         Feb `01         Mar `01
         *******         *******         *******                    *******         *******         *******
         170,235         170,235         170,235                    174,081         174,081         174,081
       1,766,048       1,595,813       1,425,578                  1,251,497       1,077,416         903,335
                                      X. 30                                                      X. 30
                                      -----                                                      -----
9th Qtr                                 $427,673             10th Qtr                              $271,000

    Apr `01          May `01         Jun `01                    Jul `01         Aug `01         Sep `01
         *******         *******         *******                    *******         *******         *******
         178,274         178,274         178,274                    183,644         184,869         *******
         725,061         546,787         368,513                    184,869         *******
                                      X. 30
11th Qtr                                $110,554
</TABLE>

The DLC also made the loan approval conditional on the review of the
Collaboration and License Agreement between The Dow Chemical Company, Dow
AgroSciences LLC, and Biosource Technologies, Inc. by the Bank's Counsel. At the
time Batik's Counsel meets with John Rakitan, Counsel for Blosource
Technologies, Inc., it is recommended that said Counsel review the issues of
loan documentation and the assignment of tile contract payments as well.

<PAGE>   16

FINANCING STATEMENT -FOLLOW INSTRUCTIONS CAREFULLY

THIS FINANCING STATEMENT IS PRESENTED FOR FILING PURSUANT TO THE UNIFORM
COMMERCIAL CODE AND WILL REMAIN EFFECTIVE, WITH CERTAIN EXCEPTIONS, FOR 5 YEARS
FROM DATE OF FILING.

<TABLE>
----------------------------------------------     ------------------------------------
<S>                                                <C>
A. NAME & TEL # OF CONTACT AT FILER (optional)     B. FILING OFFICE ACCT. # (optional)
----------------------------------------------     ------------------------------------
</TABLE>

C. RETURN COPY TO: (Name and Mailing Address
           -----------------------------------
           SIERRA WEST BANK
           1100 TEXAS ST
           FAIRFIELD, CA  94533
           -----------------------------------

<TABLE>
<S>                                            <C>                  <C>                          <C>
D. OPTIONAL DESIGNATION (IF APPLICABLE):       [ ] LESSOR/LESSEE    [ ] CONSIGNOR/CONSIGNEE      [ ] NON-UCC FILING
</TABLE>
--------------------------------------------------------------------------------

1. DEBTOR'S EXACT LEGAL NAME - insert only one debtor name (1a or 1b)

<TABLE>
<S>               <C>                           <C>                   <C>                     <C>
----------------- ---------------------------------------------------------------------------------------------
       OR         1a. ENTITY'S NAME
                  BIOSOURCE TECHNOLOGIES, INC.
----------------- ---------------------------------------------------------------------------------------------
----------------- ----------------------------- --------------------- ------------------------------- ---------
                  1b. INDIVIDUAL'S LAST NAME    FIRST NAME            MIDDLE NAME                     SUFFIX
----------------- ----------------------------- --------------------- ------------------------------- ---------
----------------------------------------------- --------------------- -------- -------------- -----------------
1c. MAILING ADDRESS                             CITY                  STATE    COUNTRY        POSTAL CODE
3333 VACA VALLEY PARKWAY, SUITE 1000            VACAVILLE             CA                      95688-9412
----------------------------------------------- --------------------- -------- -------------- -----------------
------------------ ------------- -------------- --------------------- ----------------------- -----------------
                                                                                               NONE
Id. S.S. OR TAX      OPTIONAL    1e. TYPE OF    1f. ENTITY'S STATE    1g. ENTITY'S
I.D. #             ADD'NL INFO   ENTITY         OR COUNTRY OF         ORGANIZATIONAL I.D.
77-0154648          RE ENTITY                   ORGANIZATION          #, IF ANY
                      DEBTOR
------------------ ------------- -------------- --------------------- ----------------------- -----------------
</TABLE>

2. ADDITIONAL DEBTOR'S EXACT FULL LEGAL NAME - insert only one debtor name (2a
or 2b)

<TABLE>
<S>               <C>                           <C>                   <C>                     <C>
----------------- ---------------------------------------------------------------------------------------------
       OR         2a. ENTITY'S NAME

----------------- ---------------------------------------------------------------------------------------------
----------------- ----------------------------- --------------------- ------------------------------- ---------
                  2b. INDIVIDUAL'S LAST NAME    FIRST NAME            MIDDLE NAME                     SUFFIX
----------------- ----------------------------- --------------------- ------------------------------- ---------
----------------------------------------------- --------------------- -------- -------------- -----------------
2c. MAILING ADDRESS                             CITY                  STATE    COUNTRY        POSTAL CODE

----------------------------------------------- --------------------- -------- -------------- -----------------
------------------ ------------- -------------- --------------------- ----------------------- -----------------
Id. S.S. OR TAX                                                                                NONE
I.D. #               OPTIONAL    2e. TYPE OF    2f. ENTITY'S STATE    2g. ENTITY'S
77-0154648         ADD'NL INFO   ENTITY         OR COUNTRY OF         ORGANIZATIONAL I.D.
                    RE ENTITY                   ORGANIZATION          #, IF ANY
                      DEBTOR
------------------ ------------- -------------- --------------------- ----------------------- -----------------
</TABLE>

3. SECURED PARTY'S (ORIGINAL S/P or ITS TOTAL ASSIGNEE) EXACT FULL LEGAL NAME -
insert only one secured party name (3a or 3b)

<TABLE>
<S>               <C>                           <C>                   <C>                     <C>
----------------- ---------------------------------------------------------------------------------------------
       OR         3a. ENTITY'S NAME
                  SIERRAWEST BANK
----------------- ---------------------------------------------------------------------------------------------
----------------- ----------------------------- --------------------- ------------------------------- ---------
                  3b. INDIVIDUAL'S LAST NAME    FIRST NAME            MIDDLE NAME                     SUFFIX
----------------- ----------------------------- --------------------- ------------------------------- ---------
----------------------------------------------- --------------------- -------- -------------- -----------------
3c. MAILING ADDRESS                             CITY                  STATE    COUNTRY        POSTAL CODE
1100 TEXAS ST                                   FAIRFIELD             CA                      94533
----------------------------------------------- --------------------- -------- -------------- -----------------
------------------ ------------- -------------- --------------------- ----------------------- -----------------
                                                                                               NONE
Id. S.S. OR TAX      OPTIONAL    3e. TYPE OF    3f. ENTITY'S STATE    3g. ENTITY'S
I.D. #             ADD'NL INFO   ENTITY         OR COUNTRY OF         ORGANIZATIONAL I.D.
77-0154648          RE ENTITY                   ORGANIZATION          #, IF ANY
                      DEBTOR
------------------ ------------- -------------- --------------------- ----------------------- -----------------
</TABLE>

<PAGE>   17

4. This FINANCING STATEMENT covers the following types or items of property:

ALL EQUIPMENT, CHATTEL PAPER, PERSONAL PROPERTY, ACCOUNTS RECEIVABLE, CONTRACT
RIGHTS AND INTANGIBLES, NOW OR HEREINAFTER ACQUIRED, BUT NOT INCLUDING ANY
PATENTS, COPY RIGHTS OR TRADEMARKS OR SIMILAR INTELLECTUAL PROPERTY; whether any
of the foregoing is owned now or acquired later; all accessions, additions,
replacements, and substitutions relating to any of the foregoing; all records of
any kind relating to any of the foregoing; all proceeds relating to any of the
foregoing (including insurance, general intangibles and accounts proceeds).

<TABLE>
<S>                                                                 <C>
------------------------------------------------------------------- --------------------------------------------
CHECK BOX      This FINANCING STATEMENT is signed by the Secured    7. If filed in Florida (check one)
               Party instead of the Debtor to perfect a security
   (if         interest (a) in collateral already subject to a
applicable)    security interest in another jurisdiction when it    --------------------------------------------
               was brought into this state, or when the debtor's    [ ]   Documentary          Documentary
               location was changed to this state, or (b) in              stamp tax paid       stamp tax not
               accordance with other statutory provisions                                      applicable
               (additional data may be required).
------------------------------------------------------------------- --------------------------------------------

</TABLE>

<TABLE>
<S>                                                       <C>
--------------------------------------------------------  ------------------------------------------------------------
6. REQUIRED SIGNATURE(S)                                  8.[ ] This FINANCING STATEMENT is to be filed (for
                                                                record) (or recorded) in the REAL ESTATE
       -------------------------------------------------        RECORDS
       ROBERT L. ERWIN, CHAIRMAN OF THE  BOARD                  Attach Addendum               (if applicable)

--------------------------------------------------------  ------------------------------------------------------------
                                                          9. Check to REQUEST SEARCH CERTIFICATE(S) on
                                                          Debtor(s)
       MICHAEL D. CENTRON, TREASURER                      (ADDITIONAL FEE)

                                                          (optional) [ ]   All Debtors [ ]  Debtor 1 [ ]  Debtor 2

                                                          ------------------------------------------------------------

</TABLE>

<PAGE>   18

                          ASSIGNMENT OF DEPOSIT ACCOUNT

<TABLE>
<S>                 <C>            <C>            <C>          <C>     <C>         <C>       <C>      <C>
---------------------------------------------------------------------------------------------------------------
    PRINCIPAL       LOAN DATE      MATURITY       LOAN NO      CALL    COLLATERAL  ACCOUNT   OFFICER  INITIALS
  $5,000,000.00     11-30-1998     11-30-2001     3400069949     10                 111721      274

---------------------------------------------------------------------------------------------------------------
References in the shaded area are for Lender's use only and do not limit the applicability of this document to
any particular loan or item.
---------------------------------------------------------------------------------------------------------------
</TABLE>

<TABLE>
<S>             <C>                                              <C>        <C>
BORROWER:       BIOSOURCE TECHNOLOGIES, INC.                     LENDER:    SIERRAWEST BANK
                (TIN:  77-0154648)                                          CENTRAL PACIFIC REGION
                3333 VACA VALLEY PARKWAY, SUITE 1000                        1100 TEXAS ST.
                VACAVILLE, CA  95688-9412                                   FAIRFIELD, CA  94533
---------------------------------------------------------------------------------------------------------------
</TABLE>

THIS ASSIGNMENT OF DEPOSIT ACCOUNT IS ENTERED INTO BETWEEN BIOSOURCE
TECHNOLOGIES, INC. (REFERRED TO BELOW AS "GRANTOR"); AND SIERRAWEST BANK
(REFERRED TO BELOW AS "LENDER").

ASSIGNMENT. For valuable consideration, Grantor assigns and grants to Lender a
security interest in the Collateral, including without limitation the deposit
accounts described below, to secure the Indebtedness and agrees that Lender
shall have the rights stated in this Agreement with respect to the Collateral,
in addition to all other rights which Lender may have by law.

DEFINITIONS. The following words shall have the following meanings when used in
this Agreement. Terms not otherwise defined in this Agreement shall have the
meanings attributed to such terms in the Uniform Commercial Code. All references
to dollar amounts shall mean amounts in lawful money of the United States of
America.

       ACCOUNT. The word "Account" means the deposit account described below in
       the definition for "Collateral."

       AGREEMENT. The word "Agreement" means this Assignment of Deposit Account,
       as this Assignment of Deposit Account may be amended or modified from
       time to time, together with all exhibits and schedules attached to this
       Assignment of Deposit Account from time to time.

       COLLATERAL. The word "Collateral" means the following described deposit
       account:

              CERTIFICATE OF DEPOSIT #2132399 ISSUED BY LENDER IN AN AMOUNT NOT
              LESS THAN $939,300.00

       together with (a) all interest, whether now accrued or hereafter
       accruing; (b) all additional deposits hereafter made to the Account; (c)
       any and all proceeds from the Account; and (d) all renewals, replacements
       and substitutions for any of the foregoing.

       In addition, the word "Collateral" includes all property of Grantor
       (however owned if owned by more than one person), in the possession of
       Lender (or in the possession of a third party subject to the control of
       Lender), whether existing now or later and whether tangible or intangible
       in character, including without limitation each and all of the following:

              (a) All property to which Lender acquires title or documents of
              title.

              (b) All property assigned to Lender.

              (c) All promissory notes, bills of exchange, stock certificates,
              bonds, savings passbooks, time certificates of deposit, Insurance
              policies, and all other Instruments and evidences of an
              obligation.

              (d) All records relating to any of the property described In this
              Collateral section, whether In the form of writing, microfilm,
              microfiche, or electronic media.

       EVENT OF DEFAULT. The words "Event of Default" mean and include without
       limitation any of the Events of Default set forth below in the section
       titled "Events of Default."

       GRANTOR. The word "Grantor" means BIOSOURCE TECHNOLOGIES, INC., its
       successors and assigns

       GUARANTOR. The word "Guarantor" means and includes without limitation
       each and all of the guarantors, sureties, and accommodation parties in
       connection with the Indebtedness.

       INDEBTEDNESS. The word "Indebtedness" means the indebtedness evidenced by
       the Note, including all principal and interest, together with all other
       indebtedness and costs and expenses for which Grantor is responsible
       under this Agreement or under any of the Related Documents.

       LENDER. The word "Lender" means SierraWest Bank, its successors and
       assigns.

       NOTE. The word "Note" means the note or credit agreement dated November
       30, 1998, in the principal amount of $5,000,000.00 from BIOSOURCE
       TECHNOLOGIES, INC. to Lender, together with all renewals of, extensions
       of, modifications of, refinancings of, consolidations of and
       substitutions for the note or credit agreement.

       RELATED DOCUMENTS. The words "Related Documents" mean and include without
       limitation all promissory notes, credit agreements, loan agreements,
       environmental agreements, guaranties, security agreements, mortgages,
       deeds of trust, and all other instruments, agreements and documents,
       whether now or hereafter existing, executed in connection with the
       Indebtedness.

GRANTOR'S REPRESENTATIONS AND WARRANTIES WITH RESPECT TO THE COLLATERAL. With
respect to the Collateral, Grantor represents and warrants to Lender that:

       OWNERSHIP. Grantor is the lawful owner of the Collateral free and clear
       of all loans, liens, encumbrances, and claims except as disclosed to and
       accepted by Lender in writing.

       RIGHT TO GRANT SECURITY INTEREST. Grantor has the full right, power, and
       authority to enter into this Agreement and to assign the Collateral to
       Lender.

<PAGE>   19

11-30-1998               ASSIGNMENT OF DEPOSIT ACCOUNT
LOAN NO. 3400069949               (CONTINUED)                             PAGE 2

--------------------------------------------------------------------------------

       NO FURTHER TRANSFER. Grantor will not sell, assign, encumber, or
       otherwise dispose of any of Grantor's rights in the Collateral except as
       provided in this Agreement.

       NO DEFAULTS. There are no defaults relating to the Collateral, and there
       are no offsets or counterclaims to the same. Grantor will strictly and
       promptly do everything required of Grantor under the terms, conditions,
       promises, and agreements contained in or relating to the Collateral.

       PROCEEDS. Any and all replacement or renewal certificates, instruments,
       or other benefits or proceeds related to the Collateral that are received
       by Grantor shall be held by Grantor in trust for Lender and immediately
       shall be delivered by Grantor to Lender to be held as part of the
       Collateral.

LENDER'S RIGHTS AND OBLIGATIONS WITH RESPECT TO THE COLLATERAL. While this
Agreement is in effect, Lender may retain the rights to possession of the
Collateral, together with any and all evidence of the Collateral, such as
certificates or passbooks. This Agreement will remain in effect until (a) there
no longer is any Indebtedness owing to Lender; (b) all other obligations secured
by this Agreement have been fulfilled; and (c) Grantor, in writing, has
requested from Lender a release of this Agreement.

EXPENDITURES BY LENDER. If not discharged or paid when due, Lender may (but
shall not be obligated to) discharge or pay any amounts required to be
discharged or paid by Grantor under this Agreement, including without limitation
all taxes, liens, security interests, encumbrances, and other claims, at any
time levied or placed on the Collateral. Lender also may (but shall not be
obligated to) pay all costs for insuring, maintaining and preserving the
Collateral. All such expenditures incurred or paid by Lender for such purposes
will then bear interest at the rate charged under the Note from the date
incurred or paid by Lender to the date of repayment by Grantor. All such
expenses shall become a part of the Indebtedness and, at Lender's option, will
(a) be payable on demand, (b) be added to the balance of the Note and be
apportioned among and be payable with any installment payments to become due
during either (i) the term of any applicable insurance policy or (ii) the
remaining term of the Note, or (c) be treated as a balloon payment which will be
due and payable at the Note's maturity. This Agreement also will secure payment
of these amounts. Such right shall be in addition to all other rights and
remedies to which Lender may be entitled upon the occurrence of an Event of
Default.

LIMITATIONS ON OBLIGATIONS OF LENDER. Lender shall use ordinary reasonable care
in the physical preservation and custody of any certificate or passbook for the
Collateral but shall have no other obligation to protect the Collateral or its
value. In particular, but without limitation, Lender shall have no
responsibility (a) for the collection or protection of any income on the
Collateral, (b) for the preservation of rights against issuers of the Collateral
or against third persons; (c) for ascertaining any maturates, conversions,
exchanges, offers, tenders, or similar matters relating to the Collateral; nor
(d) for informing the Grantor about any of the above, whether or not Lender has
or is deemed to have knowledge of such matters.

EVENTS OF DEFAULT. Each of the following shall constitute an Event of Default
under this Agreement:

       DEFAULT ON INDEBTEDNESS. Failure of Grantor to make any payment when due
       on the Indebtedness.

       OTHER DEFAULTS. Failure of Grantor to comply with or to perform any other
       term, obligation, covenant or condition contained in this Agreement or in
       any of the Related Documents or In any other agreement between Lender and
       Grantor.

       DEFAULT IN FAVOR OF THIRD PARTIES. Should Borrower or any Grantor default
       under any loan, extension of credit, security agreement, purchase or
       sales agreement, or any other agreement, in favor of any other creditor
       or person that may materially affect any of Borrower's property or
       Borrower's or any Grantor's ability to repay the Loans or perform their
       respective obligations under this Agreement or any of the Related
       Documents.

       FALSE STATEMENTS. Any warranty, representation or statement made or
       furnished to Lender by or on behalf of Grantor under this Agreement, the
       Name or the Related Documents is false or misleading in any material
       respect, either now or at the time made or furnished.

       DEFECTIVE COLLATERALIZATION. This Agreement or any of the Related
       Documents ceases to be in full force and effect (including failure of any
       collateral documents to create a valid and perfected security interest or
       lien) at any time and for any reason.

       INSOLVENCY. The dissolution or termination of Grantor's existence as a
       going business, the insolvency of Grantor, the appointment of a receiver
       for any part of Grantor's property, any assignment for the benefit of
       creditors, any type of creditor workout, or the commencement of any
       proceeding under any bankruptcy or insolvency laws by or against Grantor.

       CREDITOR OR FORFEITURE PROCEEDINGS. Commencement of foreclosure or
       forfeiture proceedings, whether by judicial proceeding, self-help,
       repossession or any other method, by any creditor of Grantor or by any
       governmental agency against the Collateral or any other collateral
       securing the Indebtedness. This includes a garnishment of any of
       Grantor's deposit accounts with Lender. However, this Event of Default
       shall not apply if there is a good faith dispute by Grantor as to the
       validity or reasonableness of the claim which is the basis of the
       creditor or forfeiture proceeding and if Grantor gives Lender written
       notice of the creditor or forfeiture proceeding and deposits with Lender
       monies or a surety bond for the creditor or forfeiture proceeding, in an
       amount determined by Lender, in its sole discretion, as being an adequate
       reserve or bond for the dispute.

       EVENTS AFFECTING GUARANTOR. Any of the preceding events occurs with
       respect to any Guarantor of any of the Indebtedness or such Guarantor
       dies or becomes incompetent.

       ADVERSE CHANGE. A material adverse change occurs in Grantor's financial
       condition, or Lender believes the prospect of payment or performance of
       the Indebtedness is impaired.

       RIGHT TO CURE. If any default, other than a Default on Indebtedness, is
       curable and if Grantor has not been given a prior notice of 'I breach of
       the same provision of this Agreement, it may be cured (and no Event of
       Default will have occurred) if Grantor, after Lender sends written notice
       demanding cure of such default, (a) Cures the default within fifteen (15)
       days; or (b), if the cure requires more than fifteen (15) days,
       immediately initiates steps which Lender deems in Lender's sole
       discretion to be sufficient to cure the default and thereafter continues
       and completes all reasonable and necessary steps sufficient to produce
       compliance as soon as reasonably practical.

RIGHTS AND REMEDIES ON DEFAULT. Upon the occurrence of an Event of Default, or
at any time thereafter, Lender may exercise any one or more of the following
rights and remedies, in addition to any rights or remedies that may be available
at law, in equity, or otherwise:

       ACCELERATE INDEBTEDNESS. Lender may declare all Indebtedness of Grantor
       to Lender immediately due and payable, without notice of any kind to
       Grantor.

       APPLICATION OF ACCOUNT PROCEEDS. Lender may obtain all funds in the
       Account from the issuer of the Account and apply them to the Indebtedness
       in the same manner as if the Account had been issued by Lender. If the
       Account is subject to an early withdrawal penalty, that penalty shall be
       deducted from the Account before its application to the Indebtedness,
       whether the Account is with Lender or some other institution. Any excess
       funds remaining after application of the Account proceeds to the
       Indebtedness will be paid to Grantor as the interests of Grantor may
       appear.

<PAGE>   20

11-30-1998               ASSIGNMENT OF DEPOSIT ACCOUNT
LOAN NO. 3400069949               (CONTINUED)                             PAGE 3

--------------------------------------------------------------------------------

       Grantor agrees, to the extent permitted by law, to pay any deficiency
       after application of the proceeds of the Account to the Indebtedness.
       Lender also shall have all the rights of a secured party under the
       California Uniform Commercial Code, even if the Account is not otherwise
       subject to such Code concerning security interests, and the parties to
       this Agreement agree that the provisions of the Code giving rights to a
       secured party shall nonetheless be a part of this Agreement.

       COLLECT THE COLLATERAL. Lender may collect any of the Collateral and, at
       Lender's option and to the extent permitted by applicable law, may retain
       possession of the Collateral while suing on the Indebtedness.

       SELL THE COLLATERAL. Lender may sell the Collateral, at Lender's
       discretion, as a unit or in parcels, at one or more public or private
       sales. Unless the Collateral is perishable or threatens to decline
       speedily in value, Lender shall give or mail to Grantor, or any of them,
       notice at least ten (10) days in advance of the time and place of public
       sale, or of the date after which private sale may be made. Grantor agrees
       that any requirement of reasonable notice is satisfied if Lender mails
       notice by ordinary mail addressed to Grantor, or any of them, at the last
       address Grantor has given Lender in writing. If public sale is held,
       there shall be sufficient compliance with all requirements of notice to
       the public by a single publication in any newspaper of general
       circulation in the county where the Collateral is located, setting forth
       the time and place of sale and a brief description of the property to be
       sold. Lender may be a purchaser at any public sale.

       REGISTER SECURITIES. Lender may register any securities included in the
       Collateral in Lender's name and exercise any rights normally incident to
       the ownership of securities.

       SELL SECURITIES. Lender may sell any securities included in the
       Collateral in a manner consistent with applicable federal and state
       securities laws, notwithstanding any other provision of this or any other
       agreement. If, because of restrictions under such laws, Lender is or
       believes it is unable to sell the securities in an open market
       transaction, Grantor agrees that (a) Lender shall have no obligation to
       delay sale until the securities can be registered, (b) Lender may make a
       private sale to a single person or restricted group of persons, even
       though such sale may result in a price that is less favorable than might
       be obtained in an open market transaction, and (c) such a sale shall be
       considered commercially reasonable. If any securities held as Collateral
       are "restricted securities" as defined in the Rules of the Securities and
       Exchange Commission (such as Regulation D or Rule 144) or state
       securities departments under state "Blue Sky" laws, or if Grantor, or any
       of them (if more than one), is an affiliate of the issuer of the
       securities, Grantor agrees that Grantor will neither sell nor dispose of
       any securities of such issuer without obtaining Lender's prior written
       consent.

       TRANSFER TITLE. Lender may effect transfer of title upon sale of all or
       part of the Collateral. For this purpose, Grantor irrevocably appoints
       Lender as its attorney-in-fact to execute endorsements, assignments and
       instruments in the name of Grantor and each of them (if more than one) as
       shall be necessary or reasonable.

       APPLICATION OF PROCEEDS. Lender may apply any cash which is part of the
       Collateral, or which is received from the collection or sale of the
       Collateral, to (a) reimbursement of any expenses, including any costs of
       any securities registration, commissions incurred in connection with a
       sale, attorney fees as provided below and court costs, whether or not
       there is a lawsuit and including any fees on appeal, incurred by Lender
       in connection with the collection and sale of such Collateral, and (b) to
       the payment of the Indebtedness of Grantor to Lender, with any excess
       funds to be paid to Grantor as the interests of Grantor may appear.

       OTHER RIGHTS AND REMEDIES. Lender shall have and may exercise any or all
       of the rights and remedies of a secured creditor under the provisions of
       the California Uniform Commercial Code, at law, in equity, or otherwise.

       DEFICIENCY JUDGMENT. If permitted by applicable law, Lender may obtain a
       judgment for any deficiency remaining in the Indebtedness due to Lender
       after application of all amounts received from the exercise of the rights
       provided in this section.

       CUMULATIVE REMEDIES. All of Lender's rights and remedies, whether
       evidenced by this Agreement or by any other writing, shall be cumulative
       and may be exercised singularly or concurrently. Election by Lender to
       pursue any remedy shall not exclude pursuit of any other remedy, and an
       election to make expenditures or to take action to perform an obligation
       of Grantor under this Agreement, after Grantor's failure to perform,
       shall not affect Lender's right to declare a default and to exercise its
       remedies.

MISCELLANEOUS PROVISIONS. The following miscellaneous provisions are a part of
this Agreement:

       AMENDMENTS. This Agreement, together with any Related Documents,
       constitutes the entire understanding and agreement of the parties as to
       the matters set forth in this Agreement. No alteration of or amendment to
       this Agreement shall be effective unless given in writing and signed by
       the party or parties sought to be charged or bound by the alteration or
       amendment.

       APPLICABLE LAW. This Agreement has been delivered to Lender and accepted
       by Lender in the State of California. If there is a lawsuit, Grantor
       agrees upon Lender's request to submit to the jurisdiction of the courts
       of NEVADA County, State of California. This Agreement shall be governed
       by and construed in accordance with the laws of the State of California.

       ATTORNEYS' FEES; EXPENSES. Grantor agrees to pay upon demand all of
       Lender's costs and expenses, including attorneys' fees and Lender's legal
       expenses, incurred in connection with the enforcement of this Agreement.
       Lender may pay someone else to help enforce this Agreement, and Grantor
       shall pay the costs and expenses of such enforcement. Costs and expenses
       include Lender's attorneys' fees and legal expenses whether or not there
       is a lawsuit, including attorneys' fees and legal expenses for bankruptcy
       proceedings (and including efforts to modify or vacate any automatic stay
       or injunction), appeals, and any anticipated post-judgment collection
       services. Grantor also shall pay all court costs and such additional fees
       as may be directed by the court.

       MULTIPLE PARTIES; CORPORATE AUTHORITY. All obligations of Grantor under
       this Agreement shall be joint and several, and all references to Grantor
       shall mean each and every Grantor. This means that each of the persons
       signing below is responsible for all obligations in this Agreement.

       NOTICES. All notices required to be given under this Agreement shall be
       given in writing, may be sent by telefacsimile (unless otherwise required
       by law), and shall be effective when actually delivered or when deposited
       with a nationally recognized overnight courier or deposited in the United
       States mail, first class, postage prepaid, addressed to the party to whom
       the notice is to be given at the address shown above. Any party may
       change its address for notices under this Agreement by giving formal
       written notice to the other parties, specifying that the purpose of the
       notice is to change the party's address. To the extent permitted by
       applicable law, if there is more than one Grantor, notice to any Grantor
       will constitute notice to all Grantors. For notice purposes, Grantor will
       keep Lender informed at all times of Grantor's current address(es).

       POWER OF ATTORNEY. Grantor hereby appoints Lender as its true and lawful
       attorney-in-fact, irrevocably, with full power of substitution to do the
       following: (a) to demand, collect, receive, receipt for, sue and recover
       all sums of money or other property which may now or hereafter become
       due, owing or payable from the Collateral; (b) to execute, sign and
       endorse any and all claims, instruments, receipts, checks, drafts or
       warrants issued in

<PAGE>   21

11-30-1998               ASSIGNMENT OF DEPOSIT ACCOUNT
LOAN NO. 3400069949               (CONTINUED)                             PAGE 4

--------------------------------------------------------------------------------

       payment for the Collateral; (c) to settle or compromise any and all
       claims arising under the Collateral, and, in the place and stead of
       Grantor, to execute and deliver its release and settlement for the claim;
       and (d) to file any claim or claims or to take any action or institute or
       take part in any proceedings, either in its own name or in the name of
       Grantor, or otherwise, which in the discretion of Lender may seem to be
       necessary or advisable. This power is given as security for the
       Indebtedness, and the authority hereby conferred is and shall be
       irrevocable and shall remain in full force and effect until renounced by
       Lender.

       SEVERABILITY. If a court of competent jurisdiction finds any provision of
       this Agreement to be invalid or unenforceable as to any person or
       circumstance, such finding shall not render that provision invalid or
       unenforceable as to any other persons or circumstances. If feasible, any
       such offending provision shall be deemed to be modified to be within the
       limits of enforceability or validity; however, if the offending provision
       cannot be so modified, it shall be stricken and all other provisions of
       this Agreement in all other respects shall remain valid and enforceable.

       SUCCESSOR INTERESTS. Subject to the limitations set forth above on
       transfer of the Collateral, this Agreement shall be binding upon and
       inure to the benefit of the parties, their successors and assigns.

       WAIVER. Lender shall not be deemed to have waived any rights under this
       Agreement unless such waiver is given in writing and signed by Lender. No
       delay or omission on the part of Lender in exercising any right shall
       operate as a waiver of such right or any other right. A waiver by Lender
       of a provision of this Agreement shall not prejudice or constitute a
       waiver of Lender's right otherwise to demand strict compliance with that
       provision or any other provision of this Agreement. No prior waiver by
       Lender, nor any course of dealing between Lender and Grantor, shall
       constitute a waiver of any of Lender's rights or of any of Grantor's
       obligations as to any future transactions. Whenever the consent of Lender
       is required under this Agreement, the granting of such consent by Lender
       in any instance shall not constitute continuing consent to subsequent
       instances where such consent is required and in all cases such consent
       may be granted or withheld in the sole discretion of Lender.

COLLATERAL. CERTIFICATE OF DEPOSIT # 2132399 IS TO BE MAINTAINED THROUGHOUT THE
COURSE OF THIS LOAN AND ALL SUBSEQUENT TERM LOANS THAT WILL REPAY THIS LOAN. THE
BALANCE OF THE CERTIFICATE OF DEPOSIT MAY VARY ACCORDING TO THE ADDENDUM TO THE
CREDIT APPROVAL REPORT ATTACHED.

GRANTOR ACKNOWLEDGES HAVING READ ALL THE PROVISIONS OF THIS ASSIGNMENT OF
DEPOSIT ACCOUNT AND AGREES TO ITS TERMS. THIS AGREEMENT IS DATED NOVEMBER
30,1998.

GRANTOR:

BIOSOURCE TECHNOLOGIES, INC.

By:  Robert L. Erwin                         By: Michael D. Centron
   ---------------------------------------      --------------------------------
     ROBERT L. ERWIN, CHAIRMAN OF THE BOARD      MICHAEL D. CENTRON, TREASURER.

--------------------------------------------------------------------------------

<PAGE>   22

                                 PROMISSORY NOTE

<TABLE>
<S>                <C>              <C>            <C>          <C>     <C>        <C>        <C>      <C>
---------------------------------------------------------------------------------------------------------------
    PRINCIPAL         LOAN DATE       MATURITY       LOAN NO     CALL   COLLATERAL  ACCOUNT   OFFICER  INITIALS
  $1,900,424.00      03-01-1999      10-01-2001    3400369949     10                111721      791
---------------------------------------------------------------------------------------------------------------
References in the shaded area are for Lender's use only and do not limit the applicability of this document to
any particular loan or item.
---------------------------------------------------------------------------------------------------------------
</TABLE>

BORROWER: BIOSOURCE TECHNOLOGIES, INC.           LENDER: SIERRAWEST BANK
          (TIN: 77-0154648)                              CENTRAL PACIFIC REGION
          3333 VACA VALLEY PARKWAY, SUITE 1000           1100 TEXAS ST
          VACAVILLE, CA 95688-9412                       FAIRFIELD, CA 94533
--------------------------------------------------------------------------------

<TABLE>
<S>                                     <C>                           <C>
PRINCIPAL AMOUNT: $1,900.424.00         INITIAL RATE: 7.750%          DATE OF NOTE: MARCH 1, 1999
</TABLE>

PROMISE TO PAY. BIOSOURCE TECHNOLOGIES, INC. ("Borrower") promises to pay to
SierraWest Bank ("Lender"), or order, In lawful money of the United States of
America, the principal amount of One Million Nine Hundred Thousand Four Hundred
Twenty Four & 00/100 Dollars ($1,900,424.00), together with Interest on the
unpaid principal balance from March 1, 1999, until paid In full.

PAYMENT. SUBJECT TO ANY PAYMENT CHANGES RESULTING FROM CHANGES IN THE INDEX,
BORROWER WILL PAY THIS LOAN IN 30 PAYMENTS OF $67,959.40 EACH PAYMENT AND AN
IRREGULAR LAST PAYMENT ESTIMATED AT $67,959.31. BORROWER'S FIRST PAYMENT IS DUE
APRIL 1, 1999, AND ALL SUBSEQUENT PAYMENTS ARE DUE ON THE SAME DAY OF EACH MONTH
AFTER THAT. BORROWER'S FINAL PAYMENT WILL BE DUE ON OCTOBER 1, 2001, AND WILL BE
FOR ALL PRINCIPAL AND ALL ACCRUED INTEREST NOT YET PAID. PAYMENTS INCLUDE
PRINCIPAL AND INTEREST. The annual interest rate for this Note is computed on a
365/360 basis; that is, by applying the ratio of the annual interest rate over a
year of 360 days, multiplied by the outstanding principal balance, multiplied by
the actual number of days the principal balance is outstanding. Borrower will
pay Lender at Lender's address shown above or at such other place as Lender may
designate in writing. Unless otherwise agreed or required by applicable law,
payments will be applied first to accrued unpaid interest, then to principal,
and any remaining amount to any unpaid collection costs and late charges.

VARIABLE INTEREST RATE. The interest rate on this Note is subject to change from
time to time based on changes in an independent index which is the Prime rate as
published in the western edition of the Wall Street Journal (the "Index"). The
Index is not necessarily the lowest rate charged by Lender on its loans. If the
Index becomes unavailable during the term of this loan, Lender may designate a
substitute index after notice to Borrower. Lender will tell Borrower the current
Index rate upon Borrower's request. Borrower understands that Lender may make
loans based on other rates as well. The interest rate change will not occur more
often than each DAY. THE INDEX CURRENTLY IS 7.750%. THE INTEREST RATE TO BE
APPLIED TO THE UNPAID PRINCIPAL BALANCE OF THIS NOTE WILL BE AT A RATE EQUAL TO
THE INDEX, RESULTING IN AN INITIAL RATE OF 7.750%. NOTICE: Under no
circumstances will the interest rate on this Note be more than the maximum rate
allowed by applicable law. Whenever increases occur in the interest rate,
Lender, at its option, may do one or more of the following: (a) increase
Borrower's payments to ensure Borrower's loan will pay off by its original final
maturity date, (b) increase Borrower's payments to cover accruing interest, (c)
increase the number of Borrower's payments, and (d) continue Borrower's payments
at the same amount and increase Borrower's final payment.

PREPAYMENT. Borrower may pay without penalty all or a portion of the amount owed
earlier than it is due. Early payments will not, unless agreed to by Lender in
writing, relieve Borrower of Borrower's obligation to continue to make payments
under the payment schedule. Rather, they will reduce the principal balance due
and may result in Borrower making fewer payments.

LATE CHARGE. If a payment is 10 DAYS OR MORE LATE, Borrower will be charged
5.000% of the regularly scheduled payment or $15.00, whichever is greater.

DEFAULT. Borrower will be in default if any of the following happens: (a)
Borrower fails to make any payment when due. (b) Borrower breaks any promise
Borrower has made to Lender, or Borrower fails to comply with or to perform when
due any other term, obligation, covenant, or condition contained in this Note or
any agreement related to this Note, or in any other agreement or loan Borrower
has with Lender. (c) Borrower defaults under any loan, extension of credit,
security agreement, purchase or sales agreement, or any other agreement, in
favor of any other creditor or person that may materially affect any of
Borrower's property or Borrower's ability to repay this Note or perform
Borrower's obligations under this Note or any of the Related Documents. (d) Any
representation or statement made or furnished to Lender by Borrower or on
Borrower's behalf is false or misleading in any material respect either now or
at the time made or furnished. (e) Borrower becomes insolvent, a receiver is
appointed for any part of Borrower's property, Borrower makes an assignment for
the benefit of creditors, or any proceeding is commenced either by Borrower or
against Borrower under any bankruptcy or insolvency laws. (f) Any creditor tries
to take any of Borrower's property on or in which Lender has a lien or security
interest. This includes a garnishment of any of Borrower's accounts with Lender.
(g) Any guarantor dies or any of the other events described in this default
section occurs with respect to any guarantor of this Note. (h) A material
adverse change occurs in Borrower's financial condition, or Lender believes the
prospect of payment or performance of the Indebtedness is impaired. (i) Lender
in good faith deems itself insecure.

If any default, other than a default in payment, is curable and if Borrower has
not been given a notice of a breach of the same provision of this Note within
the preceding twelve (12) months, it may be cured (and no event of default will
have occurred) if Borrower, after receiving written notice from Lender demanding
cure of such default: (a) cures the default within fifteen (15) days; or (b) if
the cure requires more than fifteen (15) days, immediately initiates steps which
Lender deems in Lender's sole discretion to be sufficient to cure the default
and thereafter continues and completes all reasonable and necessary steps
sufficient to produce compliance as soon as reasonably practical.

LENDER'S RIGHTS. Upon default, Lender may declare the entire unpaid principal
balance on this Note and all accrued unpaid interest immediately due, without
notice, and then Borrower will pay that amount. Upon Borrower's failure to pay
all amounts declared due pursuant to this section, including failure to pay upon
final maturity, Lender, at its option, may also, if permitted under applicable
law, increase the variable interest rate on this Note to 5.000 percentage points
over the Index. Lender may hire or pay someone else to help collect this Note if
Borrower does not pay. Borrower also will pay Lender that amount. This includes,
subject to any limits under applicable law, Lender's attorneys' fees and
Lender's legal expenses whether or not there is a lawsuit, including attorneys'
fees and legal expenses for bankruptcy proceedings (including efforts to modify
or vacate any automatic stay or injunction), appeals, and any anticipated
post-judgment collection services. Borrower also will pay any court costs, in
addition to all other sums provided by law. THIS NOTE HAS BEEN DELIVERED TO
LENDER AND ACCEPTED BY LENDER IN THE STATE OF CALIFORNIA. IF THERE IS A LAWSUIT,
BORROWER AGREES UPON

<PAGE>   23
03-01-1999                       PROMISSORY NOTE
LOAN NO. 3400169949                (CONTINUED)                            PAGE 3
--------------------------------------------------------------------------------

LENDER'S REQUEST TO SUBMIT TO THE JURISDICTION OF THE COURTS OF NEVADA COUNTY,
THE STATE OF CALIFORNIA. THIS NOTE SHALL BE GOVERNED BY AND CONSTRUED IN
ACCORDANCE WITH THE LAWS OF THE STATE OF CALIFORNIA.

RIGHT OF SETOFF. Borrower grants to Lender a contractual security interest in,
and hereby assigns, conveys, delivers, pledges, and transfers to Lender all
Borrower's right, title and interest in and to, Borrower's accounts with Lender
(whether checking, savings, or some other account), including without limitation
all accounts held jointly with someone also and all accounts Borrower may open
In the future, excluding however all IRA and Keogh accounts, and all trust
accounts for which the grant of a security interest would be prohibited by law.
Borrower authorizes Lender, to the extent permitted by applicable law, to charge
or setoff all sums owing on this Note against any and all such accounts.

DISBURSEMENT OF FUNDS. DISBURSEMENT OF FUNDS WITH WRITTEN REQUEST BY AUTHORIZED
SIGNERS AND PRESENTATION OF INVOICES SUPPORTING THE DOLLAR AMOUNT OF THE
REQUEST. DISBURSEMENTS WILL BE PAID TO VENDORS DIRECTLY.

GENERAL PROVISIONS. Lender may delay or forgo enforcing any of its rights or
remedies under this Note without losing them. Borrower and any other person who
signs, guarantees or endorses this Note, to the extent allowed by law, waive any
applicable statute of limitations, presentment, demand for payment, protest and
notice of dishonor. Upon any change in the terms of this Note, and unless
otherwise expressly stated in writing, no party who signs this Note, whether as
maker, guarantor, accommodation maker or endorser, shall be released from
liability. All such parties agree that Lender may renew or extend (repeatedly
and for any length of time) this loan, or release any party or guarantor or
collateral; or impair, fail to realize upon or perfect Lender's security
interest in the collateral; and take any other action deemed necessary by Lender
without the consent of or notice to anyone. All such parties also agree that
Lender may modify this loan without the consent of or notice to anyone other
than the party with whom the modification is made.

PRIOR TO SIGNING THIS NOTE, BORROWER READ AND UNDERSTOOD ALL THE PROVISIONS OF
THIS NOTE, INCLUDING THE VARIABLE INTEREST RATE PROVISIONS. BORROWER AGREES TO
THE TERMS OF THE NOTE AND ACKNOWLEDGES RECEIPT OF A COMPLETED COPY OF THE NOTE.

BORROWER:

BIOSOURCE TECHNOLOGIES, INC.

By: Robert L. Erwin                         By: Michael D. Centron
    ---------------------------------           --------------------------------
    ROBERT L. ERWIN, CHAIRMAN OF THE BOARD.     MICHAEL D. CENTRON, TREASURER

<PAGE>   24
                          ASSIGNMENT OF DEPOSIT ACCOUNT

<TABLE>
<S>                <C>            <C>            <C>           <C>      <C>        <C>         <C>      <C>
---------------------------------------------------------------------------------------------------------------
   PRINCIPAL         LOAN DATE       MATURITY       LOAN NO      CALL   COLLATERAL  ACCOUNT    OFFICER  INITIALS
 $1,900,424.00       03-01-1999     10-01-2001     3400169949     10                 111721      791
---------------------------------------------------------------------------------------------------------------
References in the shaded area are for Lender's use only and do not limit the applicability of this document to
any particular loan or item.
---------------------------------------------------------------------------------------------------------------
</TABLE>

BORROWER: BIOSOURCE TECHNOLOGIES, INC.           LENDER: SIERRAWEST BANK
          (TIN:  77-0154648)                             CENTRAL PACIFIC REGION
          3333 VACA VALLEY PARKWAY, SUITE 1000           1100 TEXAS ST.
          VACAVILLE, CA  95688-9412                      FAIRFIELD, CA  94533
--------------------------------------------------------------------------------

THIS ASSIGNMENT OF DEPOSIT ACCOUNT IS ENTERED INTO BETWEEN BIOSOURCE
TECHNOLOGIES, INC. (REFERRED TO BELOW AS "GRANTOR"); AND SIERRAWEST BANK
(REFERRED TO BELOW AS "LENDER").

ASSIGNMENT. For valuable consideration, Grantor assigns and grants to Lender a
security interest in the Collateral, including without limitation the deposit
accounts described below, to secure the Indebtedness and agrees that Lender
shall have the rights stated in this Agreement with respect to the Collateral,
in addition to all other rights which Lender may have by law.

DEFINITIONS. The following words shall have the following meanings when used in
this Agreement. Terms not otherwise defined in this Agreement shall have the
meanings attributed to such terms in the Uniform Commercial Code. All references
to dollar amounts shall mean amounts in lawful money of the United States of
America.

       ACCOUNT. The word "Account" means the deposit account described below in
       the definition for "Collateral."

       AGREEMENT. The word "Agreement" means this Assignment of Deposit Account,
       as this Assignment of Deposit Account may be amended or modified from
       time to time, together with all exhibits and schedules attached to this
       Assignment of Deposit Account from time to time.

       COLLATERAL. The word "Collateral" means the following described deposit
       account:

               CERTIFICATE OF DEPOSIT #213239 ISSUED BY LENDER IN
                      AN AMOUNT NOT LESS THAN $1,240,000.00

       together with (a) all interest, whether now accrued or hereafter
       accruing; (b) all additional deposits hereafter made to the Account; (c)
       any and all proceeds from the Account; and (d) all renewals, replacements
       and substitutions for any of the foregoing.

       In addition, the word "Collateral" includes all property of Grantor
       (however owned if owned by more than one person), in the possession of
       Lender (or in the possession of a third party subject to the control of
       Lender), whether existing now or later and whether tangible or intangible
       in character, including without limitation each and all of the following:

              (a) All property to which Lender acquires title or documents of
              title.

              (b) All property assigned to Lender.

              (c) All promissory notes, bills of exchange, stock certificates,
              bonds, savings passbooks, time certificates of deposit, insurance
              policies, and all other Instruments and evidences of an
              obligation.

              (d) All records relating to any of the property described In this
              Collateral section, whether In the form of writing, microfilm,
              microfiche, or electronic media.

       EVENT OF DEFAULT, The words "Event of Default" mean and include without
       limitation any of the Events of Default set forth below in the section
       titled "Events of Default."

       GRANTOR. The word "Grantor" means BIOSOURCE TECHNOLOGIES, INC., its
       successors and assigns

       GUARANTOR. The word "Guarantor" means and includes without limitation
       each and all of the guarantors, sureties, and accommodation parties in
       connection with the Indebtedness.

       INDEBTEDNESS. The word "Indebtedness" means the indebtedness evidenced by
       the Note, including all principal and interest, together with all other
       indebtedness and costs and expenses for which Grantor is responsible
       under this Agreement or under any of the Related Documents. In addition,
       the word "Indebtedness" includes all other obligations, debts and
       liabilities, plus interest thereon, of Grantor, or any one or more of
       them, to Lender, as well as all claims by Lender against Grantor, or any
       one or more of them, whether existing now or later; whether they are
       voluntary or involuntary, due or not due, direct or indirect, absolute or
       contingent, liquidated or unliquidated; whether Grantor may be liable
       individually or jointly with others; whether Grantor may be obligated as
       guarantor, surety, accommodation party or otherwise; whether recovery
       upon such indebtedness may be or hereafter may become barred by any
       statute of limitations; and whether such indebtedness may be or hereafter
       may become otherwise unenforceable.

       LENDER. The word "Lender" means SierraWest Bank, its successors and
       assigns.

       NOTE. The word "Note" means the note or credit agreement dated March 1,
       1999, in the principal amount of $1,900,424.00 from BIOSOURCE
       TECHNOLOGIES, INC. to Lender, together with all renewals of, extensions
       of, modifications of, refinancings of, consolidations of and
       substitutions for the note or credit agreement.

       RELATED DOCUMENTS. The words "Related Documents" mean and include without
       limitation all promissory notes, credit agreements, loan agreements,
       environmental agreements, guaranties, security agreements, mortgages,
       deeds of trust, and all other instruments, agreements and documents,
       whether now or hereafter existing, executed in connection with the
       Indebtedness.

GRANTOR'S REPRESENTATIONS AND WARRANTIES WITH RESPECT TO THE COLLATERAL. With
respect to the Collateral, Grantor represents and warrants to Lender that:

<PAGE>   25

03-01-1999                 ASSIGNMENT OF DEPOSIT ACCOUNT
LOAN NO. 3400169949                (CONTINUED)                            PAGE 3
--------------------------------------------------------------------------------

OWNERSHIP. Grantor is the lawful owner of the Collateral free and clear of all
loans, liens, encumbrances, and claims except as disclosed to and accepted by
Lender in writing.

RIGHT TO GRANT SECURITY INTEREST. Grantor has the full right, power, and
authority to enter into this Agreement and to assign the Collateral to Lender.

NO FURTHER TRANSFER. Grantor will not sell, assign, encumber, or otherwise
dispose of any of Grantor's rights in the Collateral except as provided in this
Agreement.

NO DEFAULTS. There are no defaults relating to the Collateral, and there are no
offsets or counterclaims to the same. Grantor will strictly and promptly do
everything required of Grantor under the terms, conditions, promises, and
agreements contained in or relating to the Collateral.

PROCEEDS. Any and all replacement or renewal certificates, instruments, or other
benefits or proceeds related to the Collateral that are received by Grantor
shall be held by Grantor in trust for Lender and immediately shall be delivered
by Grantor to Lender to be held as part of the Collateral.

LENDER'S RIGHTS AND OBLIGATIONS WITH RESPECT TO THE COLLATERAL. While this
Agreement is in effect, Lender may retain the rights to possession of the
Collateral, together with any and all evidence of the Collateral, such as
certificates or passbooks. This Agreement will remain in effect until (a) there
no longer is any Indebtedness owing to Lender; (b) all other obligations secured
by this Agreement have been fulfilled; and (c) Grantor, in writing, has
requested from Lender a release of this Agreement.

EXPENDITURES BY LENDER. If not discharged or paid when due, Lender may (but
shall not be obligated to) discharge or pay any amounts required to be
discharged or paid by Grantor under this Agreement, including without limitation
all taxes, liens, security interests, encumbrances, and other claims, at any
time levied or placed on the Collateral. Lender also may (but shall not be
obligated to) pay all costs for insuring, maintaining and preserving the
Collateral. All such expenditures incurred or paid by Lender for such purposes
will then bear interest at the rate charged under the Note from the date
incurred or paid by Lender to the date of repayment by Grantor. All such
expenses shall become a part of the Indebtedness and, at Lender's option, will
(a) be payable on demand, (b) be added to the balance of the Note and be
apportioned among and be payable with any installment payments to become due
during either (i) the term of any applicable insurance policy or (ii) the
remaining term of the Note, or (c) be treated as a balloon payment which will be
due and payable at the Note's maturity. This Agreement also will secure payment
of these amounts. Such right shall be in addition to all other rights and
remedies to which Lender may be entitled upon the occurrence of an Event of
Default.

LIMITATIONS ON OBLIGATIONS OF LENDER. Lender shall use ordinary reasonable care
in the physical preservation and custody of any certificate or passbook for the
Collateral but shall have no other obligation to protect the Collateral or its
value. In particular, but without limitation, Lender shall have no
responsibility (a) for the collection or protection of any income on the
Collateral, (b) for the preservation of rights against issuers of the Collateral
or against third persons; (c) for ascertaining any maturities, conversions,
exchanges, offers, tenders, or similar matters relating to the Collateral; nor
(d) for informing the Grantor about any of the above, whether or not Lender has
or is deemed to have knowledge of such matters.

EVENTS OF DEFAULT. Each of the following shall constitute an Event of Default
under this Agreement:

       DEFAULT ON INDEBTEDNESS. Failure of Grantor to make any payment when due
       on the Indebtedness.

       ENVIRONMENTAL DEFAULT. Failure of any party to comply with or perform
       when due any term, obligation, covenant or condition contained in any
       environmental agreement executed in connection with any Loan.

       OTHER DEFAULTS. Failure of Grantor to comply with or to perform any other
       term, obligation, covenant or condition contained in this Agreement or in
       any of the Related Documents or in any other agreement between Lender and
       Grantor.

       DEFAULT IN FAVOR OF THIRD PARTIES, Should Borrower or any Grantor default
       under any loan, extension of credit, security agreement, purchase or
       sales agreement, or any other agreement, in favor of any other creditor
       or person that may materially affect any of Borrower's property or
       Borrower's or any Grantor's ability to repay the Loans or perform their
       respective obligations under this Agreement or any of the Related
       Documents,

       FALSE STATEMENTS. Any warranty, representation or statement made or
       furnished to Lender by or on behalf of Grantor under this Agreement, the
       Note or the Related Documents is false or misleading in any material
       respect, either now or at the time made or furnished.

       DEFECTIVE COLLATERALIZATION. This Agreement or any of the Related
       Documents ceases to be in full force and effect (including failure of any
       collateral documents to create a valid and perfected security interest or
       lien) at any time and for any reason.

       INSOLVENCY. The dissolution or termination of Grantor's existence as a
       going business, the insolvency of Grantor, the appointment of a receiver
       for any part of Grantor's property, any assignment for the benefit of
       creditors, any type of creditor workout, or the commencement of any
       proceeding under any bankruptcy or insolvency laws by or against Grantor.

       CREDITOR OR FORFEITURE PROCEEDINGS. Commencement of foreclosure or
       forfeiture proceedings, whether by judicial proceeding, self-help,
       repossession or any other method, by any creditor of Grantor or by any
       governmental agency against the Collateral or any other collateral
       securing the Indebtedness. This includes a garnishment of any of
       Grantor's deposit accounts with Lender. However, this Event of Default
       shall not apply if there is a good faith dispute by Grantor as to the
       validity or reasonableness of the claim which is the basis of the
       creditor or forfeiture proceeding and if Grantor gives Lender written
       notice of the creditor or forfeiture proceeding and deposits with Lender
       monies or a surety bond for the creditor or forfeiture proceeding, in an
       amount determined by Lender, in its sole discretion, as being an adequate
       reserve or bond for the dispute.

       EVENTS AFFECTING GUARANTOR. Any of the preceding events occurs with
       respect to any Guarantor of any of the Indebtedness or such Guarantor
       dies or becomes incompetent.

       ADVERSE CHANGE. A material adverse change occurs in Grantor's financial
       condition, or Lender believes the prospect of payment or performance of
       the Indebtedness is impaired.

       RIGHT TO CURE. If any default, other than a Default on Indebtedness, is
       curable and if Grantor has not been given a prior notice of a breach of
       the same provision of this Agreement, it may be cured (and no Event of
       Default will have occurred) if Grantor, after Lender sends written notice
       demanding cure of such default, (a) cures the default within fifteen (15)
       days; or (b), if the cure requires more than fifteen (15) days,
       immediately initiates steps which Lender deems in Lender's sole
       discretion to be sufficient to cure the default and thereafter continues
       and completes all reasonable and necessary steps sufficient to produce
       compliance as soon as reasonably practical.

<PAGE>   26
03-01-1999                 ASSIGNMENT OF DEPOSIT ACCOUNT
LOAN NO. 3400169949                (CONTINUED)                            PAGE 4
--------------------------------------------------------------------------------

RIGHTS AND REMEDIES ON DEFAULT. Upon the occurrence of an Event of Default, or
at any time thereafter, Lender may exercise any one or more of the following
rights and remedies, in addition to any rights or remedies that may be available
at law, in equity, or otherwise:

       ACCELERATE INDEBTEDNESS. Lender may declare all Indebtedness of Grantor
       to Lender immediately due and payable, without notice of any kind to
       Grantor.

       APPLICATION OF ACCOUNT PROCEEDS. Lender may obtain all funds in the
       Account from the issuer of the Account and apply them to the Indebtedness
       in the same manner as if the Account had been issued by Lender. If the
       Account is subject to an early withdrawal penalty, that penalty shall be
       deducted from the Account before its application to the Indebtedness,
       whether the Account is with Lender or some other institution. Any excess
       funds remaining after application of the Account proceeds to the
       Indebtedness will be paid to Grantor as the interests of Grantor may
       appear. Grantor agrees, to the extent permitted by law, to pay any
       deficiency after application of the proceeds of the Account to the
       Indebtedness. Lender also shall have all the rights of a secured party
       under the California Uniform Commercial Code, even if the Account is not
       otherwise subject to such Code concerning security interests, and the
       parties to this Agreement agree that the provisions of the Code giving
       rights to a secured party shall nonetheless be a part of this Agreement,

       COLLECT THE COLLATERAL. Lender may collect any of the Collateral and, at
       Lender's option and to the extent permitted by applicable law, may retain
       possession of the Collateral while suing on the Indebtedness.

       SELL THE COLLATERAL. Lender may sell the Collateral, at Lender's
       discretion, as a unit or in parcels, at one or more public or private
       sales. Unless the Collateral is perishable or threatens to decline
       speedily in value, Lender shall give or mail to Grantor, or any of them,
       notice at least ten (10) days in advance of the time and place of public
       sale, or of the date after which private sale may be made. Grantor agrees
       that any requirement of reasonable notice is satisfied if Lender mails
       notice by ordinary mail addressed to Grantor, or any of them, at the last
       address Grantor has given Lender in writing. If public sale is held,
       there shall be sufficient compliance with all requirements of notice to
       the public by a single publication in any newspaper of general
       circulation in the county where the Collateral is located, setting forth
       the time and place of sale and a brief description of the property to be
       sold. Lender may be a purchaser at any public sale.

       REGISTER SECURITIES. Lender may register any securities included in the
       Collateral in Lender's name and exercise any rights normally incident to
       the ownership of securities.

       SELL SECURITIES. Lender may sell any securities included in the
       Collateral in a manner consistent with applicable federal and state
       securities laws, notwithstanding any other provision of this or any other
       agreement. If, because of restrictions under such laws, Lender is or
       believes it is unable to sell the securities in an open market
       transaction, Grantor agrees that (a) Lender shall have no obligation to
       delay sale until the securities can be registered, (b) Lender may make a
       private sale to a single person or restricted group of persons, even
       though such sale may result in a price that is less favorable than might
       be obtained in an open market transaction, and (c) such a sale shall be
       considered commercially reasonable. If any securities held as Collateral
       are "restricted securities" as defined in the Rules of the Securities and
       Exchange Commission (such as Regulation D or Rule 144) or state
       securities departments under state "Blue Sky" laws, or if Grantor, or any
       of them (if more than one), is an affiliate of the issuer of the
       securities, Grantor agrees that Grantor will neither sell nor dispose of
       any securities of such issuer without obtaining Lender's prior written
       consent.

       TRANSFER TITLE. Lender may effect transfer of title upon sale of all or
       part of the Collateral. For this purpose, Grantor irrevocably appoints
       Lender as its attorney- in-fact to execute endorsements, assignments and
       instruments in the name of Grantor and each of them (if more than one) as
       shall be necessary or reasonable.

       APPLICATION OF PROCEEDS. Lender may apply any cash which is part of the
       Collateral, or which is received from the collection or sale of the
       Collateral, to (a) reimbursement of any expenses, including any costs of
       any securities registration, commissions incurred in connection with a
       sale, attorney fees as provided below and court costs, whether or not
       there is a lawsuit and including any fees on appeal, incurred by Lender
       in connection with the collection and sale of such Collateral, and (b) to
       the payment of the indebtedness of Grantor to Lender, with any excess
       funds to be paid to Grantor as the interests of Grantor may appear.

       OTHER RIGHTS AND REMEDIES. Lender shall have and may exercise any or all
       of the rights and remedies of a secured creditor under the provisions of
       the California Uniform Commercial Code, at law, in equity, or otherwise.

       DEFICIENCY JUDGMENT. If permitted by applicable law, Lender may obtain a
       judgment for any deficiency remaining in the Indebtedness due to Lender
       after application of all amounts received from the exercise of the rights
       provided in this section.

       CUMULATIVE REMEDIES. All of Lender's rights and remedies, whether
       evidenced by this Agreement or by any other writing, shall be cumulative
       and may be exercised singularly or concurrently. Election by Lender to
       pursue any remedy shall not exclude pursuit of any other remedy, and an
       election to make expenditures or to take action to perform an obligation
       of Grantor under this Agreement, after Grantor's failure to perform,
       shall not affect Lender's right to declare a default and to exercise its
       remedies.

MISCELLANEOUS PROVISIONS. The following miscellaneous provisions are a part of
this Agreement:

       AMENDMENTS. This Agreement, together with any Related Documents,
       constitutes the entire understanding and agreement of the parties as to
       the matters set forth in this Agreement. No alteration of or amendment to
       this Agreement shall be effective unless given in writing and signed by
       the party or parties sought to be charged or bound by the alteration or
       amendment.

       APPLICABLE LAW. This Agreement has been delivered to Lender and accepted
       by Lender in the State of California. If there is a lawsuit, Grantor
       agrees upon Lender's request to submit to the jurisdiction of the courts
       of NEVADA County, State of California. This Agreement shall be governed
       by and construed in accordance with the laws of the State of California.

       ATTORNEYS' FEES; EXPENSES. Grantor agrees to pay upon demand all of
       Lender's costs and expenses, including attorneys' fees and Lender's legal
       expenses, incurred in connection with the enforcement of this Agreement.
       Lender may pay someone else to help enforce this Agreement, and Grantor
       shall pay the costs and expenses of such enforcement. Costs and expenses
       include Lender's attorneys' fees and legal expenses whether or not there
       is a lawsuit, including attorneys' fees and legal expenses for bankruptcy
       proceedings (and including efforts to modify or vacate any automatic stay
       or injunction), appeals, and any anticipated post-judgment collection
       services. Grantor also shall pay all court costs and such additional fees
       as may be directed by the court.

<PAGE>   27

03-01-1999                 ASSIGNMENT OF DEPOSIT ACCOUNT
LOAN NO. 3400169949                (CONTINUED)                            PAGE 5
--------------------------------------------------------------------------------

       MULTIPLE PARTIES; CORPORATE AUTHORITY. All obligations of Grantor under
       this Agreement shall be joint and several, and all references to Grantor
       shall mean each and every Grantor. This means that each of the persons
       signing below is responsible for all obligations in this Agreement.

       NOTICES. All notices required to be given under this Agreement shall be
       given in writing, may be sent by telefacsimile (unless otherwise required
       by law), and shall be effective when actually delivered or when deposited
       with a nationally recognized overnight courier or deposited in the United
       States mail, first class, postage prepaid, addressed to the party to whom
       the notice is to be given at the address shown above. Any party may
       change its address for notices under this Agreement by giving formal
       written notice to the other parties, specifying that the purpose of the
       notice is to change the party's address. To the extent permitted by
       applicable law, if there is more than one Grantor, notice to any Grantor
       will constitute notice to all Grantors. For notice purposes, Grantor will
       keep Lender informed at all times of Grantor's current address(es).

       POWER OF ATTORNEY. Grantor hereby appoints Lender as its true and lawful
       attorney-in-fact, irrevocably, with full power of substitution to do the
       following: (a) to demand, collect, receive, receipt for, sue and recover
       all sums of money or other property which may now or hereafter become
       due, owing or payable from the Collateral; (b) to execute, sign and
       endorse any and all claims, instruments, receipts, checks, drafts or
       warrants issued in payment for the Collateral; (c) to settle or
       compromise any and all claims arising under the Collateral, and, in the
       place and stead of Grantor, to execute and deliver its release and
       settlement for the claim; and (d) to file any claim or claims or to take
       any action or institute or take part in any proceedings, either in its
       own name or in the name of Grantor, or otherwise, which in the discretion
       of Lender may seem to be necessary or advisable. This power is given as
       security for the Indebtedness, and the authority hereby conferred is and
       shall be irrevocable and shall remain in full force and effect until
       renounced by Lender.

       SEVERABILITY. If a court of competent jurisdiction finds any provision of
       this Agreement to be invalid or unenforceable as to any person or
       circumstance, such finding shall not render that provision invalid or
       unenforceable as to any other persons or circumstances. If feasible, any
       such offending provision shall be deemed to be modified to be within the
       limits of enforceability or validity; however, if the offending provision
       cannot be so modified, it shall be stricken and all other provisions of
       this Agreement in all other respects shall remain valid and enforceable.

       SUCCESSOR INTERESTS. Subject to the limitations set forth above on
       transfer of the Collateral, this Agreement shall be binding upon and
       inure to the benefit of the parties, their successors and assigns.

       WAIVER. Lender shall not be deemed to have waived any rights under this
       Agreement unless such waiver is given In writing and signed by Lender. No
       delay or omission on the part of Lender in exercising any right shall
       operate as a waiver of such right or any other right. A waiver by Lender
       of a provision of this Agreement shall not prejudice or constitute a
       waiver of Lender's right otherwise to demand strict compliance with that
       provision or any other provision of this Agreement. No prior waiver by
       Lender, nor any course of dealing between Lender and Grantor, shall
       constitute a waiver of any of Lender's rights or of any of Grantor's
       obligations as to any future transactions. Whenever the consent of Lender
       is required under this Agreement, the granting of such consent by Lender
       in any instance shall not constitute continuing consent to subsequent
       instances where such consent is required and in all cases such consent
       may be granted or withheld in the sole discretion of Lender.

GRANTOR ACKNOWLEDGES HAVING READ ALL THE PROVISIONS OF THIS ASSIGNMENT OF
DEPOSIT ACCOUNT AND AGREES TO ITS TERMS. THIS AGREEMENT IS DATED MARCH 1, 1999.

GRANTOR:

BIOSOURCE TECHNOLOGIES, INC.

By: Robert L. Erwin                         By: Michael D. Centron
    ---------------------------------           --------------------------------
    ROBERT L. ERWIN, CHAIRMAN OF THE BOARD      MICHAEL D. CENTRON, TREASURER

--------------------------------------------------------------------------------

<PAGE>   28

                          COMMERCIAL SECURITY AGREEMENT

<TABLE>
<S>                <C>            <C>            <C>           <C>      <C>        <C>        <C>      <C>
---------------------------------------------------------------------------------------------------------------
    PRINCIPAL        LOAN DATE      MATURITY       LOAN NO      CALL    COLLATERAL  ACCOUNT   OFFICER  INITIALS
  $1,900,424.00     03-01-1999     10-01-2001     3400169949     10                 111721      791
---------------------------------------------------------------------------------------------------------------
References in the shaded area are for Lender's use only and do not limit the applicability of this document to
any particular loan or item.
---------------------------------------------------------------------------------------------------------------
</TABLE>

BORROWER: BIOSOURCE TECHNOLOGIES, INC.           LENDER: SIERRAWEST BANK
          (TIN:  77-0154648)                             CENTRAL PACIFIC REGION
          3333 VACA VALLEY PARKWAY, SUITE 1000           1100 TEXAS ST.
          VACAVILLE, CA  95688-9412                      FAIRFIELD, CA  94533
--------------------------------------------------------------------------------

THIS COMMERCIAL SECURITY AGREEMENT IS ENTERED INTO BETWEEN BIOSOURCE
TECHNOLOGIES, INC. (REFERRED TO BELOW AS "GRANTOR"); AND SIERRAWEST BANK
(REFERRED TO BELOW AS "LENDER"). FOR VALUABLE CONSIDERATION, GRANTOR GRANTS TO
LENDER A SECURITY INTEREST IN THE COLLATERAL TO SECURE THE INDEBTEDNESS AND
AGREES THAT LENDER SHALL HAVE THE RIGHTS STATED IN THIS AGREEMENT WITH RESPECT
TO THE COLLATERAL, IN ADDITION TO ALL OTHER RIGHTS WHICH LENDER MAY HAVE BY LAW.

DEFINITIONS. The following words shall have the following meanings when used in
this Agreement. Terms not otherwise defined in this Agreement shall have the
meanings attributed to such terms in the Uniform Commercial Code. All references
to dollar amounts shall mean amounts in lawful money of the United States of
America.

       AGREEMENT. The word "Agreement" means this Commercial Security Agreement,
       as this Commercial Security Agreement may be amended or modified from
       time to time, together with all exhibits and schedules attached to this
       Commercial Security Agreement from time to time.

       COLLATERAL. The word "Collateral" means the following described property
       of Grantor, whether now owned or hereafter acquired, whether now existing
       or hereafter arising, and wherever located:

              ALL EQUIPMENT, CHATTEL PAPER, PERSONAL PROPERTY, ACCOUNTS
              RECEIVABLE, CONTRACT RIGHTS AND INTANGIBLES, NOW OR HEREAFTER
              ACQUIRED, BUT NOT INCLUDING ANY PATENTS, COPY RIGHTS OR TRADEMARKS
              OR SIMILAR INTELLECTUAL PROPERTY

       In addition, the word "Collateral" includes all the following, whether
       now owned or hereafter acquired, whether now existing or hereafter
       arising, and wherever located:

              (a) All attachments, accessions, accessories, tools, parts,
              supplies, increases, and additions to and all replacements of and
              substitutions for any property described above.

              (b) All products and produce of any of the property described in
              this Collateral section.

              (c) All accounts, general intangibles, instruments, rents, monies,
              payments, and all other rights, arising out of a sale, lease, or
              other disposition of any of the property described in this
              Collateral section.

              (d) All proceeds (including insurance proceeds) from the sale,
              destruction, loss, or other disposition of any of the property
              described in this Collateral section.

              (e) All records and data relating to any of the property described
              in this Collateral section, whether in the form of a writing,
              photograph, microfilm, microfiche, or electronic media, together
              with all of Grantor's right, title, and interest in and to all
              computer software required to utilize, create, maintain, and
              process any such records or data on electronic media.

       EVENT OF DEFAULT. The words "Event of Default" mean and include without
       limitation any of the Events of Default set forth below in the section
       titled "Events of Default."

       GRANTOR. The word "Grantor" means BIOSOURCE TECHNOLOGIES, INC., its
       successors and assigns

       GUARANTOR. The word "Guarantor" means and includes without limitation
       each and all of the guarantors, sureties, and accommodation parties in
       connection with the Indebtedness.

       INDEBTEDNESS. The word "Indebtedness" means the indebtedness evidenced by
       the Note, including all principal and interest, together with all other
       indebtedness and costs and expenses for which Grantor is responsible
       under this Agreement or under any of the Related Documents.

       LENDER. The word "Lender" means SierraWest Bank, its successors and
       assigns.

       NOTE. The word "Note" means the note or credit agreement dated March 1,
       1999, in the principal amount of $1,900,424.00 from BIOSOURCE
       TECHNOLOGIES, INC. to Lender, together with all renewals of, extensions
       of, modifications of, refinancings of, consolidations of and
       substitutions for the note or credit agreement.

       RELATED DOCUMENTS. The words "Related Documents" mean and include without
       limitation all promissory notes, credit agreements, loan agreements,
       environmental agreements, guaranties, security agreements, mortgages,
       deeds of trust, and all other instruments, agreements and documents,
       whether now or hereafter existing, executed in connection with the
       Indebtedness.

RIGHT OF SETOFF. Grantor hereby grants Lender a contractual security interest in
and hereby assigns, conveys, delivers, pledges, and transfers all of Grantor's
right, title and interest in and to Grantor's accounts with Lender (whether
checking, savings, or some other account), including all accounts held jointly
with someone else and all accounts Grantor may open in the future, excluding,
however, all IRA and Keogh accounts, and all trust accounts for which the grant
of a security interest would be prohibited by law. Grantor authorizes Lender, to
the extent permitted by applicable law, to charge or setoff all Indebtedness
against any and all such accounts.

OBLIGATIONS OF GRANTOR. Grantor warrants and covenants to Lender as follows:

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       PERFECTION OF SECURITY INTEREST. Grantor agrees to execute such financing
       statements and to take whatever other actions are requested by Lender to
       perfect and continue Lender's security interest in the Collateral. Upon
       request of Lender, Grantor will deliver to Lender any and all of the
       documents evidencing or constituting the Collateral, and Grantor will
       note Lender's interest upon any and all chattel paper if not delivered to
       Lender for possession by Lender. Grantor hereby appoints Lender as its
       irrevocable attorney-in-fact for the purpose of executing any documents
       necessary to perfect or to continue the security interest granted in this
       Agreement. Lender may at any time, and without further authorization from
       Grantor, file a carbon, photographic or other reproduction of any
       financing statement or of this Agreement for use as a financing
       statement. Grantor will reimburse Lender for all expenses for the
       perfection and the continuation of the perfection of Lender's security
       interest in the Collateral. Grantor promptly will notify Lender before
       any change in Grantor's name including any change to the assumed business
       names of Grantor.

       NO VIOLATION, The execution and delivery of this Agreement will not
       violate any law or agreement governing Grantor or to which Grantor is a
       party, and its certificate or articles of incorporation and bylaws do not
       prohibit any term or condition of this Agreement.

       ENFORCEABILITY OF COLLATERAL. To the extent the Collateral consists of
       accounts, chattel paper, or general intangibles, the Collateral is
       enforceable in accordance with its terms, is genuine, and complies with
       applicable laws concerning form, content and manner of preparation and
       execution, and all persons appearing to be obligated on the Collateral
       have authority and capacity to contract and are in fact obligated as they
       appear to be on the Collateral.

       LOCATION OF THE COLLATERAL. Grantor, upon request of Lender, will deliver
       to Lender in form satisfactory to Lender a schedule of real properties
       and Collateral locations relating to Grantor's operations, including
       without limitation the following: (a) all real property owned or being
       purchased by Grantor; (b) all real property being rented or leased by
       Grantor; (c) all storage facilities owned, rented, leased, or being used
       by Grantor; and (d) all other properties where Collateral is or may be
       located. Except in the ordinary course of its business, Grantor shall not
       remove the Collateral from its existing locations without the prior
       written consent of Lender.

       REMOVAL OF COLLATERAL. Grantor shall keep the Collateral (or to the
       extent the Collateral consists of intangible property such as accounts,
       the records concerning the Collateral) at Grantor's address shown above,
       or at such other locations as are acceptable to Lender. Except in the
       ordinary course of its business, including the sales of inventory,
       Grantor shall not remove the Collateral from its existing locations
       without the prior written consent of Lender. To the extent that the
       Collateral consists of vehicles, or other titled property, Grantor shall
       not take or permit any action which would require application for
       certificates of title for the vehicles outside the State of California,
       without the prior written consent of Lender.

       TRANSACTIONS INVOLVING COLLATERAL. Except for inventory sold or accounts
       collected in the ordinary course of Grantor's business, Grantor shall not
       sell, offer to sell, or otherwise transfer or dispose of the Collateral.
       While Grantor is not in default under this Agreement, Grantor may sell
       inventory, but only in the ordinary course of its business and only to
       buyers who quality as a buyer in the ordinary course of business. A sale
       in the ordinary course of Grantor's business does not include a transfer
       in partial or total satisfaction of a debt or any bulk sale. Grantor
       shall not pledge, mortgage, encumber or otherwise permit the Collateral
       to be subject to any lien, security interest, encumbrance, or charge,
       other than the security interest provided for in this Agreement, without
       the prior written consent of Lender. This includes security interests
       even if junior in right to the security interests granted under this
       Agreement. Unless waived by Lender, all proceeds from any disposition of
       the Collateral (for whatever reason) shall be held in trust for Lender
       and shall not be commingled with any other funds; provided however, this
       requirement shall not constitute consent by Lender to any sale or other
       disposition. Upon receipt, Grantor shall immediately deliver any such
       proceeds to Lender.

       TITLE. Grantor represents and warrants to Lender that it holds good and
       marketable title to the Collateral, free and clear of all liens and
       encumbrances except for the lien of this Agreement. No financing
       statement covering any of the Collateral is on file in any public office
       other than those which reflect the security interest created by this
       Agreement or to which Lender has specifically consented. Grantor shall
       defend Lender's rights in the Collateral against the claims and demands
       of all other persons.

       COLLATERAL SCHEDULES AND LOCATIONS. Insofar as the Collateral consists of
       inventory, Grantor shall deliver to Lender, as often as Lender shall
       require, such lists, descriptions, and designations of such Collateral as
       Lender may require to identify the nature, extent, and location of such

       COLLATERAL. Such information shall be submitted for Grantor and each of
       its subsidiaries or related companies.

       MAINTENANCE AND INSPECTION OF COLLATERAL. Grantor shall maintain all
       tangible Collateral in good condition and repair. Grantor will not commit
       or permit damage to or destruction of the Collateral or any part of the
       Collateral, Lender and its designated representatives and agents shall
       have the right at all reasonable times to examine, inspect, and audit the
       Collateral wherever located. Grantor shall immediately notify Lender of
       all cases involving the return, rejection, repossession, loss or damage
       of or to any Collateral; of any request for credit or adjustment or of
       any other dispute arising with respect to the Collateral; and generally
       of all happenings and events affecting the Collateral or the value or the
       amount of the Collateral.

       TAXES, ASSESSMENTS AND LIENS. Grantor will pay when due all taxes,
       assessments and liens upon the Collateral, its use or operation, upon
       this Agreement, upon any promissory note or notes evidencing the
       Indebtedness, or upon any of the other Related Documents. Grantor may
       withhold any such payment or may elect to contest any lien if Grantor is
       in good faith conducting an appropriate proceeding to contest the
       obligation to pay and so long as Lender's interest in the Collateral is
       not jeopardized in Lender's sole opinion. If the Collateral is subjected
       to a lien which is not discharged within fifteen (15) days, Grantor shall
       deposit with Lender cash, a sufficient corporate surety bond or other
       security satisfactory to Lender in an amount adequate to provide for the
       discharge of the lien plus any interest, costs, attorneys' fees or other
       charges that could accrue as a result of foreclosure or sale of the
       Collateral. In any contest Grantor shall defend itself and Lender and
       shall satisfy any final adverse judgment before enforcement against the
       Collateral. Grantor shall name Lender as an additional obligee under any
       surety bond furnished in the contest proceedings.

       COMPLIANCE WITH GOVERNMENTAL REQUIREMENTS. Grantor shall comply promptly
       with all laws, ordinances, rules and regulations of all governmental
       authorities, including without limitation all environmental laws,
       ordinances, rules and regulations, now or hereafter in effect, applicable
       to the ownership, production, disposition, or use of the Collateral.
       Grantor may contest in good faith any such law, ordinance or regulation
       and withhold compliance during any proceeding, including appropriate
       appeals, so long as Lender's interest in the Collateral, in Lender's
       opinion, is not jeopardized.

       MAINTENANCE OF CASUALTY INSURANCE. Grantor shall procure and maintain all
       risks insurance, including without limitation fire, theft and liability
       coverage together with such other insurance as Lender may require with
       respect to the Collateral, in form, amounts, coverages and basis
       reasonably acceptable to Lender and issued by a company or companies
       reasonably acceptable to Lender. Grantor, upon request of Lender, will
       deliver to Lender from time to time the policies or certificates of
       insurance in form satisfactory to Lender, including stipulations that
       coverages will
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       not be cancelled or diminished without at least ten (10) days' prior
       written notice to Lender and not including any disclaimer of the
       insurer's liability for failure to give such a notice. Each insurance
       policy also shall include an endorsement providing that coverage in favor
       of Lender will not be impaired in any way by any act, omission or default
       of Grantor or any other person. In connection with all policies covering
       assets in which Lender holds or is offered a security interest, Grantor
       will provide Lender with such loss payable or other endorsements as
       Lender may require. In no event shall the insurance be in an amount less
       than the amount agreed upon in the Agreement to Provide Insurance. If
       Grantor at any time fails to obtain or maintain any insurance as required
       under this Agreement, Lender may (but shall not be obligated to) obtain
       such insurance as Lender deems appropriate, including if it so chooses
       "single interest insurance," which will cover only Lender's interest in
       the Collateral.

       APPLICATION OF INSURANCE PROCEEDS. Grantor shall promptly notify Lender
       of any loss or damage to the Collateral. Lender may make proof of loss if
       Grantor fails to do so within fifteen (15) days of the casualty. All
       proceeds of any insurance on the Collateral, including accrued proceeds
       thereon, shall be held by Lender as part of the Collateral. If Lender
       consents to repair or replacement of the damaged or destroyed Collateral,
       Lender shall, upon satisfactory proof of expenditure, pay or reimburse
       Grantor from the proceeds for the reasonable cost of repair or
       restoration. If Lender does not consent to repair or replacement of the
       Collateral, Lender shall retain a sufficient amount of the proceeds to
       pay all of the Indebtedness, and shall pay the balance to Grantor. Any
       proceeds which have not been disbursed within six (6) months after their
       receipt and which Grantor has not committed to the repair or restoration
       of the Collateral shall be used to prepay the Indebtedness.

       INSURANCE RESERVES. Lender may require Grantor to maintain with Lender
       reserves for payment of insurance premiums, which reserves shall be
       created by monthly payments from Grantor of a sum estimated by Lender to
       be sufficient to produce, at least fifteen (15) days before the premium
       due date, amounts at least equal to the insurance premiums to be paid. If
       fifteen (15) days before payment is due, the reserve funds are
       insufficient, Grantor shall upon demand pay any deficiency to Lender. The
       reserve funds shall be held by Lender as a general deposit and shall
       constitute a non-interest-bearing account which Lender may satisfy by
       payment of the insurance premiums required to be paid by Grantor as they
       become due. Lender does not hold the reserve funds in trust for Grantor,
       and Lender is not the agent of Grantor for payment of the insurance
       premiums required to be paid by Grantor. The responsibility for the
       payment of premiums shall remain Grantor's sole responsibility.

       INSURANCE REPORTS. Grantor, upon request of Lender, shall furnish to
       Lender reports on each existing policy of insurance showing such
       information as Lender may reasonably request including the following: (a)
       the name of the insurer; (b) the risks insured; (c) the amount of the
       policy; (d) the property insured; (e) the then current value on the basis
       of which insurance has been obtained and the manner of determining that
       value; and (f) the expiration date of the policy. In addition, Grantor
       shall upon request by Lender (however not more often than annually) have
       an independent appraiser satisfactory to Lender determine, as applicable,
       the cash value or replacement cost of the Collateral.

GRANTOR'S RIGHT TO POSSESSION. Until default, Grantor may have possession of the
tangible personal property and beneficial use of all the Collateral and may use
it in any lawful manner not inconsistent with this Agreement or the Related
Documents, provided that Grantor's right to possession and beneficial use shall
not apply to any Collateral where possession of the Collateral by Lender is
required by law to perfect lender's security interest in such Collateral. If
Lender at any time has possession of any Collateral, whether before or after an
Event of Default, Lender shall be deemed to have exercised reasonable care in
the custody and preservation of the Collateral if Lender takes such action for
that purpose as Grantor shall request or as Lender, in Lender's sole discretion,
shall deem appropriate under the circumstances, but failure to honor any request
by Grantor shall not of itself be deemed to be a failure to exercise reasonable
care. Lender shall not be required to take any steps necessary to preserve any
rights in the Collateral against prior parties, nor to protect, preserve or
maintain any security interest given to secure the Indebtedness.

EXPENDITURES BY LENDER. If not discharged or paid when due, Lender may (but
shall not be obligated to) discharge or pay any amounts required to be
discharged or paid by Grantor under this Agreement, including without limitation
all taxes, liens, security interests, encumbrances, and other claims, at any
time levied or placed on the Collateral. Lender also may (but shall not be
obligated to) pay all costs for insuring, maintaining and preserving the
Collateral. All such expenditures incurred or paid by Lender for such purposes
will then bear interest at the rate charged under the Note from the date
incurred or paid by Lender to the date of repayment by Grantor. All such
expenses shall become a part of the Indebtedness and, at Lender's option, will
(a) be payable on demand, (b) be added to the balance of the Note and be
apportioned among and be payable with any installment payments to become due
during either (i) the term of any applicable insurance policy or (ii) the
remaining term of the Note, or (c) be treated as a balloon payment which will be
due and payable at the Note's maturity. This Agreement also will secure payment
of these amounts. Such right shall be in addition to all other rights and
remedies to which Lender may be entitled upon the occurrence of an Event of
Default.

EVENTS OF DEFAULT. Each of the following shall constitute an Event of Default
under this Agreement:

       DEFAULT ON INDEBTEDNESS. Failure of Grantor to make any payment when due
       on the Indebtedness.

       ENVIRONMENTAL DEFAULT. Failure of any party to comply with or perform
       when due any term, obligation, covenant or condition contained in any
       environmental agreement executed in connection with any Loan.

       OTHER DEFAULTS. Failure of Grantor to comply with or to perform any other
       term, obligation, covenant or condition contained in this Agreement or in
       any of the Related Documents or in any other agreement between Lender and
       Grantor.

       DEFAULT IN FAVOR OF THIRD PARTIES. Should Borrower or any Grantor default
       under any loan, extension of credit, security agreement, purchase or
       sales agreement, or any other agreement, in favor of any other creditor
       or person that may materially affect any of Borrower's property or
       Borrower's or any Grantor's ability to repay the Loans or perform their
       respective obligations under this Agreement or any of the Related
       Documents.

       FALSE STATEMENTS. Any warranty, representation or statement made or
       furnished to Lender by or on behalf of Grantor under this Agreement, the
       Note or the Related Documents is false or misleading in any material
       respect, either now or at the time made or furnished.

       DEFECTIVE COLLATERALIZATION. This Agreement or any of the Related
       Documents ceases to be in full force and effect (including failure of any
       collateral documents to create a valid and perfected security interest or
       lien) at any time and for any reason.

       INSOLVENCY. The dissolution or termination of Grantor's existence as a
       going business, the insolvency of Grantor, the appointment of a receiver
       for any part of Grantor's property, any assignment for the benefit of
       creditors, any type of creditor workout, or the commencement of any
       proceeding under any bankruptcy or insolvency laws by or against Grantor.

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       CREDITOR OR FORFEITURE PROCEEDINGS. Commencement of foreclosure or
       forfeiture proceedings, whether by judicial proceeding, self-help,
       repossession or any other method, by any creditor of Grantor or by any
       governmental agency against the collateral or any other collateral
       securing the Indebtedness. This includes a garnishment of any of
       Grantor's deposit accounts with Lender. However, this Event of Default
       shall not apply if there is a good faith dispute by Grantor as to the
       validity or reasonableness of the claim which is the basis of the
       creditor or forfeiture proceeding and if Grantor gives Lender written
       notice of the creditor or forfeiture proceeding and deposits with Lender
       monies or a surety bond for the creditor or forfeiture proceeding, in an
       amount determined by Lender, in its sole discretion, as being an adequate
       reserve or bond for the dispute.

       EVENTS AFFECTING GUARANTOR. Any of the preceding events occurs with
       respect to any Guarantor of any of the Indebtedness or such Guarantor
       dies or becomes incompetent. Lender, at its option, may, but shall not be
       required to, permit the Guarantor's estate to assume unconditionally the
       obligations arising under the guaranty in a manner satisfactory to
       Lender, and, in doing so, cure the Event of Default.

       ADVERSE CHANGE. A material adverse change occurs in Grantor's financial
       condition, or Lender believes the prospect of payment or performance of
       the Indebtedness is impaired.

       RIGHT TO CURE. It any default, other than a Default on Indebtedness, is
       curable and if Grantor has not been given a prior notice of a breach of
       the same provision of this Agreement, it may be cured (and no Event of
       Default will have occurred) if Grantor, after Lender sends written notice
       demanding cure of such default, (a) cures the default within fifteen (15)
       days; or (b), if the cure requires more than fifteen (15) days,
       immediately initiates steps which Lender deems in Lender's sole
       discretion to be sufficient to cure the default and thereafter continues
       and completes all reasonable and necessary steps sufficient to produce
       compliance as soon as reasonably practical.

RIGHTS AND REMEDIES ON DEFAULT. If an Event of Default occurs under this
Agreement, at any time thereafter, Lender shall have all the rights of a secured
party under the California Uniform Commercial Code. In addition and without
limitation, Lender may exercise any one or more of the following rights and
remedies:

       ACCELERATE INDEBTEDNESS. Lender may declare the entire Indebtedness,
       including any prepayment penalty which Grantor would be required to pay,
       immediately due and payable, without notice.

       ASSEMBLE COLLATERAL. Lender may require Grantor to deliver to Lender all
       or any portion of the Collateral and any and all certificates of title
       and other documents relating to the Collateral. Lender may require
       Grantor to assemble the Collateral and make it available to Lender at a
       place to be designated by Lender. Lender also shall have full power to
       enter upon the property of Grantor to take possession of and remove the
       Collateral. If the Collateral contains other goods not covered by this
       Agreement at the time of repossession, Grantor agrees Lender may take
       such other goods, provided that Lender makes reasonable efforts to return
       them to Grantor after repossession.

       SELL THE COLLATERAL. Lender shall have full power to sell, lease,
       transfer, or otherwise deal with the Collateral or proceeds thereof in
       its own name or that of Grantor. Lender may sell the Collateral at public
       auction or private sale. Unless the Collateral threatens to decline
       speedily in value or is of a type customarily sold on a recognized
       market, Lender will give Grantor reasonable notice of the time after
       which any private sale or any other intended disposition of the
       Collateral is to be made. The requirements of reasonable notice shall be
       met if such notice is given at least ten (10) days, or such lesser time
       as required by state law, before the time of the sale or disposition. All
       expenses relating to the disposition of the Collateral, including without
       limitation the expenses of retaking, holding, insuring, preparing for
       sale and selling the Collateral, shall become a part of the Indebtedness
       secured by this Agreement and shall be payable on demand, with interest
       at the Note rate from date of expenditure until repaid.

       APPOINT RECEIVER. To the extent permitted by applicable law, Lender shall
       have the following rights and remedies regarding the appointment of a
       receiver: (a) Lender may have a receiver appointed as a matter of right,
       (b) the receiver may be an employee of Lender and may serve without bond,
       and (c) all fees of the receiver and his or her attorney shall become
       part of the Indebtedness secured by this Agreement and shall be payable
       on demand, with interest at the Note rate from date of expenditure until
       repaid.

       COLLECT REVENUES, APPLY ACCOUNTS. Lender, either itself or through a
       receiver, may collect the payments, rents, income, and revenues from the
       Collateral. Lender may at any time in its discretion transfer any
       Collateral into its own name or that of its nominee and receive the
       payments, rents, income, and revenues therefrom and hold the same as
       security for the Indebtedness or apply it to payment of the Indebtedness
       in such order of preference as Lender may determine. Insofar as the
       Collateral consists of accounts, general intangibles, insurance policies,
       instruments, chattel paper, choses in action, or similar property, Lender
       may demand, collect, receipt for, settle, compromise, adjust, sue for,
       foreclose, or realize on the Collateral as Lender may determine, whether
       or not Indebtedness or Collateral is then due. For these purposes, Lender
       may, on behalf of and in the name of Grantor, receive, open and dispose
       of mail addressed to Grantor; change any address to which mail and
       payments are to be sent; and endorse notes, checks, drafts, money orders,
       documents of title, instruments and items pertaining to payment,
       shipment, or storage of any Collateral. To facilitate collection, Lender
       may notify account debtors and obligors on any Collateral to make
       payments directly to Lender.

       OBTAIN DEFICIENCY. If Lender chooses to sell any or all of the
       Collateral, Lender may obtain a judgment against Grantor for any
       deficiency remaining on the Indebtedness due to Lender after application
       of all amounts received from the exercise of the rights provided in this
       Agreement. Grantor shall be liable for a deficiency even if the
       transaction described in this subsection is a sale of accounts or chattel
       paper.

       OTHER RIGHTS AND REMEDIES. Lender shall have all the rights and remedies
       of a secured creditor under the provisions of the Uniform Commercial
       Code, as may be amended from time to time. In addition, Lender shall have
       and may exercise any or all other rights and remedies it may have
       available at law, in equity, or otherwise.

       CUMULATIVE REMEDIES. All of Lender's rights and remedies, whether
       evidenced by this Agreement or the Related Documents or by any other
       writing, shall be cumulative and may be exercised singularly or
       concurrently. Election by Lender to pursue any remedy shall not exclude
       pursuit of any other remedy, and an election to make expenditures or to
       take action to perform an obligation of Grantor under this Agreement,
       after Grantor's failure to perform, shall not affect Lender's right to
       declare a default and to exercise its remedies.

MISCELLANEOUS PROVISIONS. The following miscellaneous provisions are a part of
this Agreement:

       AMENDMENTS. This Agreement, together with any Related Documents,
       constitutes the entire understanding and agreement of the parties as to
       the matters set forth in this Agreement. No alteration of or amendment to
       this Agreement shall be effective unless given in writing and signed by
       the party or parties sought to be charged or bound by the alteration or
       amendment.

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       APPLICABLE LAW. This Agreement has been delivered to Lender and accepted
       by Lender in the State of California. It there is a lawsuit, Grantor
       agrees upon Lender's request to submit to the jurisdiction of the courts
       of NEVADA County, the State of California. This Agreement shall be
       governed by and construed in accordance with the laws of the State of
       California.

       ATTORNEYS' FEES; EXPENSES. Grantor agrees to pay upon demand all of
       Lender's costs and expenses, including attorneys' fees and Lender's legal
       expenses, incurred in connection with the enforcement of this Agreement.
       Lender may pay someone else to help enforce this Agreement, and Grantor
       shall pay the costs and expenses of such enforcement. Costs and expenses
       include Lender's attorneys' fees and legal expenses whether or not there
       is a lawsuit, including attorneys' fees and legal expenses for bankruptcy
       proceedings (and including efforts to modify or vacate any automatic stay
       or injunction), appeals, and any anticipated post-judgment collection
       services. Grantor also shall pay all court costs and such additional fees
       as may be directed by the court.

       CAPTION HEADINGS. Caption headings in this Agreement are for convenience
       purposes only and are not to be used to interpret or define the
       provisions of this Agreement.

       MULTIPLE PARTIES; CORPORATE AUTHORITY. All obligations of Grantor under
       this Agreement shall be joint and several, and all references to Grantor
       shall mean each and every Grantor. This means that each of the persons
       signing below is responsible for all obligations in this Agreement.

       NOTICES. All notices required to be given under this Agreement shall be
       given in writing, may be sent by telefacsimile (unless otherwise required
       by law), and shall be effective when actually delivered or when deposited
       with a nationally recognized overnight courier or deposited in the United
       States mail, first class, postage prepaid, addressed to the party to whom
       the notice is to be given at the address shown above. Any party may
       change its address for notices under this Agreement by giving formal
       written notice to the other parties, specifying that the purpose of the
       notice is to change the party's address. To the extent permitted by
       applicable law, if there is more than one Grantor, notice to any Grantor
       will constitute notice to all Grantors. For notice purposes, Grantor will
       keep Lender informed at all times of Grantor's current address(es).

       POWER OF ATTORNEY. Grantor hereby appoints Lender as its true and lawful
       attorney-in-fact, irrevocably, with full power of substitution to do the
       following: (a) to demand, collect, receive, receipt for, sue and recover
       all sums of money or other property which may now or hereafter become
       due, owing or payable from the Collateral; (b) to execute, sign and
       endorse any and all claims, instruments, receipts, checks, drafts or
       warrants issued in payment for the Collateral; (c) to settle or
       compromise any and all claims arising under the Collateral, and, in the
       place and stead of Grantor, to execute and deliver its release and
       settlement for the claim; and (d) to file any claim or claims or to take
       any action or institute or take part in any proceedings, either in its
       own name or in the name of Grantor, or otherwise, which in the discretion
       of Lender may seem to be necessary or advisable. This power is given as
       security for the Indebtedness, and the authority hereby conferred is and
       shall be irrevocable and shall remain in full force and effect until
       renounced by Lender.

       PREFERENCE PAYMENTS. Any monies Lender pays because of an asserted
       preference claim in Borrower's bankruptcy will become a part of the
       Indebtedness and, at Lender's option, shall be payable by Borrower as
       provided above in the "EXPENDITURES BY LENDER" paragraph.

       SEVERABILITY. If a court of competent jurisdiction finds any provision of
       this Agreement to be invalid or unenforceable as to any person or
       circumstance, such finding shall not render that provision invalid or
       unenforceable as to any other persons or circumstances. If feasible, any
       such offending provision shall be deemed to be modified to be within the
       limits of enforceability or validity; however, if the offending provision
       cannot be so modified, it shall be stricken and all other provisions of
       this Agreement in all other respects shall remain valid and enforceable.

       SUCCESSOR INTERESTS. Subject to the limitations set forth above on
       transfer of the Collateral, this Agreement shall be binding upon and
       inure to the benefit of the parties, their successors and assigns.

       WAIVER. Lender shall not be deemed to have waived any rights under this
       Agreement unless such waiver is given in writing and signed by Lender. No
       delay or omission on the part of Lender in exercising any right shall
       operate as a waiver of such right or any other right. A waiver by Lender
       of a provision of this Agreement shall not prejudice or constitute a
       waiver of Lender's right otherwise to demand strict compliance with that
       provision or any other provision of this Agreement. No prior waiver by
       Lender, nor any course of dealing between Lender and Grantor, shall
       constitute a waiver of any of Lender's rights or of any of Grantor's
       obligations as to any future transactions. Whenever the consent of Lender
       is required under this Agreement, the granting of such consent by Lender
       in any instance shall not constitute continuing consent to subsequent
       instances where such consent is required and in all cases such consent
       may be granted or withheld in the sole discretion of Lender.

       WAIVER OF CO-OBLIGOR'S RIGHTS. If more than one person is obligated for
       the Indebtedness, Borrower irrevocably waives, disclaims and relinquishes
       all claims against such other person which Borrower has or would
       otherwise have by virtue of payment of the Indebtedness or any part
       thereof, specifically including but not limited to all rights of
       indemnity, contribution or exoneration.

GRANTOR ACKNOWLEDGES HAVING READ ALL THE PROVISIONS OF THIS COMMERCIAL SECURITY
AGREEMENT, AND GRANTOR AGREES TO ITS TERMS. THIS AGREEMENT IS DATED MARCH 1,
1999.

GRANTOR:

BIOSOURCE TECHNOLOGIES, INC.

By: Robert L. Erwin                          By: Michael D. Centron
    --------------------------------------       -------------------------------
    ROBERT L. ERWIN, CHAIRMAN OF THE BOARD       MICHAEL D. CENTRON, TREASURER

--------------------------------------------------------------------------------

<PAGE>   33

                             BUSINESS LOAN AGREEMENT

<TABLE>
<S>                 <C>            <C>            <C>           <C>     <C>         <C>       <C>      <C>
---------------------------------------------------------------------------------------------------------------
    PRINCIPAL        LOAN DATE      MATURITY       LOAN NO      CALL    COLLATERAL  ACCOUNT   OFFICER  INITIALS
  $1,900,424.00     03-01-1999     10-01-2001     3400169949     10                 111721      791
---------------------------------------------------------------------------------------------------------------
References in the shaded area are for Lender's use only and do not limit the applicability of this document to
any particular loan or item.
---------------------------------------------------------------------------------------------------------------
</TABLE>

BORROWER: BIOSOURCE TECHNOLOGIES, INC.           LENDER: SIERRAWEST BANK
          (TIN:  77-0154648)                             CENTRAL PACIFIC REGION
          3333 VACA VALLEY PARKWAY, SUITE 1000           1100 TEXAS ST.
          VACAVILLE, CA  95688-9412                      FAIRFIELD, CA  94533
================================================================================

THIS BUSINESS LOAN AGREEMENT BETWEEN BIOSOURCE TECHNOLOGIES, INC. ("BORROWER")
AND SIERRAWEST BANK ("LENDER") IS MADE AND EXECUTED ON THE FOLLOWING TERMS AND
CONDITIONS. BORROWER HAS RECEIVED PRIOR COMMERCIAL LOANS FROM LENDER OR HAS
APPLIED TO LENDER FOR A COMMERCIAL LOAN OR LOANS AND OTHER FINANCIAL
ACCOMMODATIONS, INCLUDING THOSE WHICH MAY BE DESCRIBED ON ANY EXHIBIT OR
SCHEDULE ATTACHED TO THIS AGREEMENT. ALL SUCH LOANS AND FINANCIAL
ACCOMMODATIONS, TOGETHER WITH ALL FUTURE LOANS AND FINANCIAL ACCOMMODATIONS FROM
LENDER TO BORROWER, ARE REFERRED TO IN THIS AGREEMENT INDIVIDUALLY AS THE "LOAN"
AND COLLECTIVELY AS THE "LOANS." BORROWER UNDERSTANDS AND AGREES THAT: (a) IN
GRANTING, RENEWING, OR EXTENDING ANY LOAN, LENDER IS RELYING UPON BORROWER'S
REPRESENTATIONS, WARRANTIES, AND AGREEMENTS, AS SET FORTH IN THIS AGREEMENT; (b)
THE GRANTING, RENEWING, OR EXTENDING OF ANY LOAN BY LENDER AT ALL TIMES SHALL BE
SUBJECT TO LENDER'S SOLE JUDGMENT AND DISCRETION; AND (c) ALL SUCH LOANS SHALL
BE AND SHALL REMAIN SUBJECT TO THE FOLLOWING TERMS AND CONDITIONS OF THIS
AGREEMENT.

TERM. This Agreement shall be effective as of March 16, 1999, and shall continue
thereafter until all Indebtedness of Borrower to Lender has been performed in
full and the parties terminate this Agreement in writing.

DEFINITIONS. The following words shall have the following meanings when used in
this Agreement. Terms not otherwise defined in this Agreement shall have the
meanings attributed to such terms in the Uniform Commercial Code. All references
to dollar amounts shall mean amounts in lawful money of the United States of
America.

       AGREEMENT. The word "Agreement" means this Business Loan Agreement, as
       this Business Loan Agreement may be amended or modified from time to
       time, together with all exhibits and schedules attached to this Business
       Loan Agreement from time to time.

       BORROWER. The word "Borrower" means BIOSOURCE TECHNOLOGIES, INC.. The
       word "Borrower" also includes, as applicable, all subsidiaries and
       affiliates of Borrower as provided below in the paragraph titled
       "Subsidiaries and Affiliates."

       COLLATERAL. The word "Collateral" means and includes without limitation
       all property and assets granted as collateral security for a Loan,
       whether real or personal property, whether granted directly or
       indirectly, whether granted now or in the future, and whether granted in
       the form of a security interest, mortgage, deed of trust, assignment,
       pledge, chattel mortgage, chattel trust, factor's lion, equipment trust,
       conditional sale, trust receipt, lien, charge, lien or title retention
       contract, lease or consignment intended as a security device, or any
       other security or lien interest whatsoever, whether created by law,
       contract, or otherwise.

       ERISA. The word "ERISA" means the Employee Retirement Income Security Act
       of 1974, as amended.

       EVENT OF DEFAULT. The words "Event of Default" moan and include without
       limitation any of the Events of Default set forth below in the section
       titled "EVENTS OF DEFAULT."

       GRANTOR. The word "Grantor" means and includes without limitation each
       and all of the persons or entities granting a Security Interest in any
       Collateral for the Indebtedness, including without limitation all
       Borrowers granting such a Security Interest.

       GUARANTOR. The word "Guarantor" means and includes without limitation
       each and all of the guarantors, sureties, and accommodation parties in
       connection with any Indebtedness.

       INDEBTEDNESS. The word "Indebtedness" means and includes without
       limitation all Loans, together with all other obligations, debts and
       liabilities of Borrower to Lender, or any one or more of them, as well as
       all claims by Lender against Borrower, or any one or more of them;
       whether now or hereafter existing, voluntary or involuntary, due or not
       due, absolute or contingent, liquidated or unliquidated; whether Borrower
       may be liable individually or jointly with others; whether Borrower may
       be obligated as a guarantor, surety, or otherwise; whether recovery upon
       such Indebtedness may be or hereafter may become barred by any statute of
       limitations; and whether such Indebtedness may be or hereafter may become
       otherwise unenforceable.

       LENDER. The word "Lender" means SierraWest Bank, its successors and
       assigns.

       LOAN. The word "Loan" or "Loans" means and includes without limitation
       any and all commercial loans and financial accommodations from Lender to
       Borrower, whether now or hereafter existing, and however evidenced,
       including without limitation those loans and financial accommodations
       described herein or described on any exhibit or schedule attached to this
       Agreement from time to time.

       NOTE. The word "Note" means and includes without limitation Borrower's
       promissory note or notes, if any, evidencing Borrower's Loan obligations
       in favor of Lender, as well as any substitute, replacement or refinancing
       note or notes therefor.

       PERMITTED LIENS. The words "Permitted Liens" mean: (a) liens and security
       interests securing Indebtedness owed by Borrower to Lender; (b) liens for
       taxes, assessments, or similar charges either not yet due or being
       contested in good faith; (c) liens of materialmen, mechanics,
       warehousemen, or carriers, or other like liens arising in the ordinary
       course of business and securing obligations which are not yet delinquent;
       (d) purchase money liens or purchase money security interests upon or in
       any property acquired or held by Borrower in the ordinary course of
       business to secure indebtedness outstanding on the date of this Agreement
       or permitted to be incurred under the paragraph of this Agreement titled
       "Indebtedness and Liens"; (e) liens and security interests which, as of
       the date of this Agreement, have been disclosed to and approved by the
       Lender in writing; and (f) those liens and security interests which in
       the aggregate constitute an immaterial and insignificant monetary amount
       with respect to the net value of Borrower's assets.

<PAGE>   34

03-01-1999                  BUSINESS LOAN AGREEMENT
LOAN NO. 3400169949                (CONTINUED)                            PAGE 2
--------------------------------------------------------------------------------

       RELATED DOCUMENTS. The words "Related Documents" mean and include without
       limitation all promissory notes, credit agreements, loan agreements,
       environmental agreements, guaranties, security agreements, mortgages,
       deeds of trust, and all other instruments, agreements and documents,
       whether now or hereafter existing, executed in connection with the
       Indebtedness.

       SECURITY AGREEMENT. The words "Security Agreement" mean and include
       without limitation any agreements, promises, covenants, arrangements,
       understandings or other agreements, whether created by law, contract, or
       otherwise. evidencing, governing, representing, or creating a Security
       Interest.

       SECURITY INTEREST. The words "Security Interest" mean and include without
       limitation any type of collateral security, whether in the form of a
       lien, charge, mortgage, deed of trust, assignment, pledge, chattel
       mortgage, chattel trust, factor's lien, equipment trust, conditional
       sale, trust receipt, lien or title retention contract, lease or
       consignment intended as a security device, or any other security or lien
       interest whatsoever, whether created by law, contract, or otherwise,

CONDITIONS PRECEDENT TO EACH ADVANCE. Lender's obligation to make the initial
Loan Advance and each subsequent Loan Advance under this Agreement shall be
subject to the fulfillment to Lender's satisfaction of all of the conditions set
forth in this Agreement and in the Related Documents.

       LOAN DOCUMENTS. Borrower shall provide to Lender in form satisfactory to
       Lender the following documents for the Loan: (a) the Note, (b) Security
       Agreements granting to Lender security interests in the Collateral, (c)
       Financing Statements perfecting Lender's Security Interests; (d) evidence
       of insurance as required below; and (e) any other documents required
       under this Agreement or by Lender or its counsel.

       BORROWER'S AUTHORIZATION. Borrower shall have provided in form and
       substance satisfactory to Lender properly certified resolutions, duly
       authorizing the execution and delivery of this Agreement, the Note and
       the Related Documents, and such other authorizations and other documents
       and instruments as Lender or its counsel, in their sole discretion, may
       require.

       PAYMENT OF FEES AND EXPENSES. Borrower shall have paid to Lender all
       fees, charges, and other expenses which are then due and payable as
       specified in this Agreement or any Related Document.

       REPRESENTATIONS AND WARRANTIES. The representations and warranties set
       forth in this Agreement, in the Related Documents, and in any document or
       certificate delivered to Lender under this Agreement are true and
       correct.

       NO EVENT OF DEFAULT. There shall not exist at the time of any advance a
       condition which would constitute an Event of Default under this
       Agreement.

REPRESENTATIONS AND WARRANTIES. Borrower represents and warrants to Lender, as
of the date of this Agreement, as of the date of each disbursement of Loan
proceeds, as of the date of any renewal, extension or modification of any Loan,
and at all times any Indebtedness exists:

       ORGANIZATION. Borrower is a corporation which is duly organized, validly
       existing, and in good standing under the laws of the State of California
       and is validly existing and in good standing in all states in which
       Borrower is doing business. Borrower has the full power and authority to
       own its properties and to transact the businesses in which it Is
       presently engaged or presently proposes to engage. Borrower also is duly
       qualified as a foreign corporation and is in good standing in all states
       in which the failure to so quality would have a material adverse effect
       on its businesses or financial condition.

       AUTHORIZATION. The execution, delivery, and performance of this Agreement
       and all Related Documents by Borrower, to the extent to be executed,
       delivered or performed by Borrower, have been duly authorized by all
       necessary action by Borrower; do not require the consent or approval of
       any other person, regulatory authority or governmental body; and do not
       conflict with, result in a violation of, or constitute a default under
       (a) any provision of its articles of incorporation or organization, or
       bylaws, or any agreement or other instrument binding upon Borrower or (b)
       any law, governmental regulation, court decree, or order applicable to
       Borrower.

       FINANCIAL INFORMATION. Each financial statement of Borrower supplied to
       Lender truly and completely disclosed Borrower's financial condition as
       of the date of the statement, and there has been no material adverse
       change in Borrower's financial condition subsequent to the date of the
       most recent financial statement supplied to Lender. Borrower has no
       material contingent obligations except as disclosed in such financial
       statements.

       LEGAL EFFECT. This Agreement constitutes, and any instrument or agreement
       required hereunder to be given by Borrower when delivered will
       constitute, legal, valid and binding obligations of Borrower enforceable
       against Borrower in accordance with their respective terms.

       PROPERTIES. Except as contemplated by this Agreement or as previously
       disclosed in Borrower's financial statements or in writing to Lender and
       as accepted by Lender, and except for property tax liens for taxes not
       presently due and payable, Borrower owns and has good title to all of
       Borrower's properties free and clear of all Security Interests, and has
       not executed any security documents or financing statements relating to
       such properties. All of Borrower's properties are titled in Borrower's
       legal name, and Borrower has not used, or filed a financing statement
       under, any other name for at least the last five (5) years.

       LITIGATION AND CLAIMS. No litigation, claim, investigation,
       administrative proceeding or similar action (including those for unpaid
       taxes) against Borrower is pending or threatened, and no other event has
       occurred which may materially adversely affect Borrower's financial
       condition or properties, other than litigation, claims, or other events,
       if any, that have been disclosed to and acknowledged by Lender in
       writing.

       TAXES. To the best of Borrower's knowledge, all tax returns and reports
       of Borrower that are or were required to be filed, have been filed, and
       all taxes, assessments and other governmental charges have been paid in
       full, except those presently being or to be contested by Borrower in good
       faith in the ordinary course of business and for which adequate reserves
       have been provided.

       LIEN PRIORITY. Unless otherwise previously disclosed to Lender in
       writing, Borrower has not entered into or granted any Security
       Agreements, or permitted the filing or attachment of any Security
       Interests on or affecting any of the Collateral directly or indirectly
       securing repayment of Borrower's Loan and Note, that would be prior or
       that may in any way be superior to Lender's Security Interests and rights
       in and to such Collateral.

       BINDING EFFECT. This Agreement, the Note, all Security Agreements
       directly or indirectly securing repayment of Borrower's Loan and Note and
       all of the Related Documents are binding upon Borrower as well as upon
       Borrower's successors, representatives and assigns, and are legally
       enforceable in accordance with their respective terms.

       COMMERCIAL PURPOSES. Borrower intends to use the Loan proceeds solely for
       business or commercial related purposes.

<PAGE>   35

03-01-1999                  BUSINESS LOAN AGREEMENT
LOAN NO. 3400169949                (CONTINUED)                            PAGE 3
--------------------------------------------------------------------------------

       EMPLOYEE BENEFIT PLANS. Each employee benefit plan as to which Borrower
       may have any liability complies in all material respects with all
       applicable requirements of law and regulations, and (I) no Reportable
       Event nor Prohibited Transaction (as defined in ERISA) has occurred with
       respect to any such plan, (ii) Borrower has not withdrawn from any such
       plan or initiated steps to do so, (III) no steps have been taken to
       terminate any such plan, and (iv) there are no unfunded liabilities other
       than those previously disclosed to Lender in writing.

       LOCATION OF BORROWER'S OFFICES AND RECORDS. Borrower's place of business,
       or Borrower's Chief executive office, if Borrower has more than one place
       of business, is located at 3333 VACA VALLEY PARKWAY, SUITE 1000,
       VACAVILLE, CA 95688-9412. Unless Borrower has designated otherwise in
       writing this location is also the office or offices where Borrower keeps
       its records concerning the Collateral.

       INFORMATION. All information heretofore or contemporaneously herewith
       furnished by Borrower to Lender for the purposes of or in connection with
       this Agreement or any transaction contemplated hereby is, and all
       information hereafter furnished by or on behalf of Borrower to Lender
       will be, true and accurate in every material respect on the date as of
       which such information is dated or certified; and none of such
       information is or will be incomplete by omitting to state any material
       fact necessary to make such information not misleading.

       SURVIVAL OF REPRESENTATIONS AND WARRANTIES. Borrower understands and
       agrees that Lender, without independent investigation, is relying upon
       the above representations and warranties in making the above referenced
       Loan to Borrower. Borrower further agrees that the foregoing
       representations and warranties shall be continuing in nature and shall
       remain in full force and effect until such time as Borrower's
       Indebtedness shall be paid in full, or until this Agreement shall be
       terminated in the manner provided above, whichever is the last to occur.

AFFIRMATIVE COVENANTS. Borrower covenants and agrees with Lender that, while
this Agreement is in effect, Borrower will:

       LITIGATION. Promptly inform Lender in writing of (a) all material adverse
       changes in Borrower's financial condition, and (b) all existing and all
       threatened litigation, claims, investigations, administrative proceedings
       or similar actions affecting Borrower or any Guarantor which could
       materially affect the financial condition of Borrower or the financial
       condition of any Guarantor.

       FINANCIAL RECORDS. Maintain its books and records in accordance with
       generally accepted accounting principles, applied on a consistent basis,
       and permit Lender to examine and audit Borrower's books and records at
       all reasonable times.

       ADDITIONAL INFORMATION. Furnish such additional information and
       statements, lists of assets and liabilities, agings of receivables and
       payables, inventory schedules, budgets, forecasts, tax returns, and other
       reports with respect to Borrower's financial condition and business
       operations as Lender may request from time to time.

       INSURANCE. Maintain fire and other risk insurance, public liability
       insurance, and such other insurance as Lender may require with respect to
       Borrower's properties and operations, in form, amounts, coverages and
       with insurance companies reasonably acceptable to Lender. Borrower, upon
       request of Lender, will deliver to Lender from time to time the policies
       or certificates of insurance in form satisfactory to Lender, including
       stipulations that coverages will not be cancelled or diminished without
       at least ten (10) days' prior written notice to Lender. Each insurance
       policy also shall include an endorsement providing that coverage in favor
       of Lender will not be impaired in any way by any act, omission or default
       of Borrower or any other person. In connection with all policies covering
       assets in which Lender holds or is offered a security interest for the
       Loans, Borrower will provide Lender with such loss payable or other
       endorsements as Lender may require.

       INSURANCE REPORTS. Furnish to Lender, upon request of Lender, reports on
       each existing insurance policy showing such information as Lender may
       reasonably request, including without limitation the following: (a) the
       name of the insurer; (b) the risks insured; (c) the amount of the policy;
       (d) the properties insured; (e) the then current property values on the
       basis of which insurance has been obtained, and the manner of determining
       those values; and (f) the expiration date of the policy. In addition,
       upon request of Lender (however not more often than annually), Borrower
       will have an independent appraiser satisfactory to Lender determine, as
       applicable, the actual cash value or replacement cost of any Collateral.
       The cost of such appraisal shall be paid by Borrower.

       OTHER AGREEMENTS. Comply with all terms and conditions of all other
       agreements, whether now or hereafter existing, between Borrower and any
       other party and notify Lender immediately in writing of any default in
       connection with any other such agreements.

       LOAN PROCEEDS. Use all Loan proceeds solely for Borrower's business
       operations, unless specifically consented to the contrary by Lender in
       writing.

       TAXES, CHARGES AND LIENS. Pay and discharge when due all of its
       indebtedness and obligations, including without limitation all
       assessments, taxes, governmental charges, levies and liens, of every kind
       and nature, imposed upon Borrower or its properties, income, or profits,
       prior to the date on which penalties would attach, and all lawful claims
       that, if unpaid, might become a lion or charge upon any of Borrower's
       properties, income, or profits. Provided however, Borrower will not be
       required to pay and discharge any such assessment, tax, charge, levy,
       lien or claim so long as (a) the legality of the same shall be contested
       in good faith by appropriate proceedings, and (b) Borrower shall have
       established on its books adequate reserves with respect to such contested
       assessment, tax, charge, levy, lien, or claim in accordance with
       generally accepted accounting practices. Borrower, upon demand of Lender,
       will furnish to Lender evidence of payment of the assessments, taxes,
       charges, levies, liens and claims and will authorize the appropriate
       governmental official to deliver to Lender at any time a written
       statement of any assessments, taxes, charges, levies, liens and claims
       against Borrower's properties, income, or profits.

       PERFORMANCE. Perform and comply with all terms, conditions, and
       provisions set forth in this Agreement and in the Related Documents in a
       timely manner, and promptly notify Lender if Borrower learns of the
       occurrence of any event which constitutes an Event of Default under this
       Agreement or under any of the Related Documents.

       OPERATIONS. Maintain executive and management personnel with
       substantially the same qualifications and experience as the present
       executive and management personnel; provide written notice to Lender of
       any change in executive and management personnel; conduct its business
       affairs in a reasonable and prudent manner and In compliance with all
       applicable federal, state and municipal laws, ordinances, rules and
       regulations respecting its properties, charters, businesses and
       operations, including without limitation, compliance with the Americans
       With Disabilities Act and with all minimum funding standards and other
       requirements of ERISA and other laws applicable to Borrower's employee
       benefit plans.

       INSPECTION. Permit employees or agents of Lender at any reasonable time
       to inspect any and all Collateral for the Loan or Loans and Borrower's
       other properties and to examine or audit Borrower's books, accounts, and
       records and to make copies and memoranda of Borrower's books, accounts,
       and records. If Borrower now or at any time hereafter maintains any
       records (including without limitation computer generated records and
<PAGE>   36

03-01-1999                  BUSINESS LOAN AGREEMENT
LOAN NO. 3400169949                (CONTINUED)                            PAGE 4
--------------------------------------------------------------------------------

       computer software programs for the generation of such records) in the
       possession of a third party, Borrower, upon request of Lender, shall
       notify such party to permit Lender free access to such records at all
       reasonable times and to provide Lender with copies of any records it may
       request, all at Borrower's expense.

       COMPLIANCE CERTIFICATE. Unless waived in writing by Lender, provide
       Lender at least annually and at the time of each disbursement of Loan
       proceeds with a certificate executed by Borrower's chief financial
       officer, or other officer or person acceptable to Lender, certifying that
       the representations and warranties set forth in this Agreement are true
       and correct as of the date of the certificate and further certifying
       that, as of the date of the certificate, no Event of Default exists under
       this Agreement.

       ENVIRONMENTAL COMPLIANCE AND REPORTS. Borrower shall comply in all
       respects with all covenants, terms, conditions and provisions set forth
       in the Environmental Indemnity Certificate and Agreement executed in
       connection with the Loan.

       ADDITIONAL ASSURANCES. Make, execute and deliver to Lender such
       promissory notes, mortgages, deeds of trust, security agreements,
       financing statements, instruments, documents and other agreements as
       Lender or its attorneys may reasonably request to evidence and secure the
       Loans and to perfect all Security Interests.

NEGATIVE COVENANTS. Borrower covenants and agrees with Lender that while this
Agreement is in effect, Borrower shall not, without the prior written consent of
Lender:

       INDEBTEDNESS AND LIENS. (a) Except for trade debt incurred in the normal
       course of business and indebtedness to Lender contemplated by this
       Agreement, create, incur or assume indebtedness for borrowed money,
       including capital leases, (b) except as allowed as a Permitted Lien,
       sell, transfer, mortgage, assign, pledge, lease, grant a security
       interest in, or encumber any of Borrower's assets, or (c) sell with
       recourse any of Borrower's accounts, except to Lender.

       CONTINUITY OF OPERATIONS. (a) Engage in any business activities
       substantially different than those in which Borrower is presently
       engaged, (b) cease operations, liquidate, merge, transfer, acquire or
       consolidate with any other entity, change ownership, change its name,
       dissolve or transfer or sell Collateral out of the ordinary course of
       business, (c) pay any dividends on Borrower's stock (other than dividends
       payable in its stock), provided, however that notwithstanding the
       foregoing, but only so long as no Event of Default has occurred and is
       continuing or would result from the payment of dividends, if Borrower is
       a "Subchapter S Corporation" (as defined in the Internal Revenue Code of
       1986, as amended), Borrower may pay cash dividends on its stock to its
       shareholders from time to time in amounts necessary to enable the
       shareholders to pay income taxes and make estimated income tax payments
       to satisfy their liabilities under federal and state law which arise
       solely from their status as Shareholders of a Subchapter S Corporation
       because of their ownership of shares of stock of Borrower, or (d)
       purchase or retire any of Borrower's outstanding shares or alter or amend
       Borrower's capital structure.

       LOANS, ACQUISITIONS AND GUARANTIES. (a) Loan, invest in or advance money
       or assets, (b) purchase, create or acquire any interest in any other
       enterprise or entity, or (c) incur any obligation as surety or guarantor
       other than in the ordinary course of business.

CESSATION OF ADVANCES. If Lender has made any commitment to make any Loan to
Borrower, whether under this Agreement or under any other agreement, Lender
shall have no obligation to make Loan Advances or to disburse Loan proceeds if:
(a) Borrower or any Guarantor is in default under the terms of this Agreement or
any of the Related Documents or any other agreement that Borrower or any
Guarantor has with Lender; (b) Borrower or any Guarantor becomes insolvent,
files a petition in bankruptcy or similar proceedings, or is adjudged a
bankrupt; (c) there occurs a material adverse change in Borrower's financial
condition, in the financial condition of any Guarantor, or in the value of any
Collateral securing any Loan; (d) any Guarantor seeks, claims or otherwise
attempts to limit, modify or revoke such Guarantor's guaranty of the Loan or any
other loan with Lender; or (a) Lender in good faith deems itself insecure, even
though no Event of Default shall have occurred.

FINANCIAL COVENANTS.

1. ANNUALLY AUDITED FINANCIAL STATEMENTS WITHIN 90 DAYS OF FISCAL YEAR END.

2. QUARTERLY INTERNAL FINANCIAL STATEMENTS WITHIN 45 DAYS OF EACH PERIOD.

3. BORROWER TO PROVIDE MONTHLY INVOICES, OPERATING BUDGET AND CAPITAL PURCHASES
BUDGET WITHIN 30 DAYS OF EACH PERIOD.

4. BORROWER TO PROVIDE BANK WITH ANY PERTINENT REVISIONS TO DOW CHEMICAL
COLLABORATION AND LICENSE AGREEMENT.

5. BORROWER TO MAINTAIN CERTIFICATE OF DEPOSIT #2132399 AS PROVIDED FOR IN THE
ASSIGNMENT OF DEPOSIT ACCOUNT AND THE CREDIT APPROVAL REPORT ATTACHED THERETO.

DISBURSEMENT OF FUNDS. DISBURSEMENT OF FUNDS WITH WRITTEN REQUEST BY AUTHORIZED
SIGNERS AND PRESENTATION OF INVOICES SUPPORTING THE DOLLAR AMOUNT OF THE
REQUEST. DISBURSEMENTS WILL BE PAID TO VENDORS DIRECTLY.

PAYMENT TERMS.

BORROWER WILL PAY THIS LOAN IN ACCORDANCE WITH THE FOLLOWING PAYMENT SCHEDULE:
INTEREST ONLY PAYMENTS WILL BE REQUIRED MONTHLY BEGINNING JANUARY 1, 1999. THERE
IS TO BE FOUR ADVANCE PERIODS DURING THE TERM OF THIS NOTE. THE FIRST BEGINNING
ON THIS DATE AND ENDING FEBRUARY 28, 1999. THE SECOND BEGINNING MARCH 1, 1999
AND ENDING MAY 31, 1999. THE THIRD BEGINNING JUNE 1, 1999 AND ENDING AUGUST 31,
1999. THE FOURTH AND FINAL ADVANCE PERIOD BEGINNING SEPTEMBER 1, 1999 AND ENDING
NOVEMBER 30,1999. THE OUTSTANDING BALANCE ON THE LAST DAY OF EACH ADVANCE PERIOD
WILL BE PAID IN FULL BY A NEW NOTE ADVANCE FROM A SEPARATE TERM LOAN TO BE
PROVIDED BY SIERRAWEST BANK THAT WILL AMORTIZE SAID Principal BALANCE IN FULL BY
OCTOBER 1, 2001.

HAZARDOUS SUBSTANCES. The terms "hazardous waste," "hazardous substance,"
"disposal", "release," and "threatened release," as used in this Agreement,
shall have the same meanings as set forth in the "CERCLA," "SARA," the Hazardous
Materials Transportation Act, 40 U.S.C. Section 1801, et seq., the Resource
Conservation and Recovery Act, 42 U.S.C. Section 6901, et seq., Chapters 6.5
through 7.7 of Division 20 of the California Health and Safety Code, Section
25100, et seq., or other applicable state or Federal laws, rules, or regulations
adopted pursuant to any of the foregoing. Except as disclosed to and
acknowledged by Lender in writing, Borrower represents and warrants that : (a)
During the period of Borrower's ownership of the properties, there has been no
unauthorized use, generation, manufacture, storage, treatment, disposal, release
or threatened release of any

<PAGE>   37
03-01-1999                  BUSINESS LOAN AGREEMENT
LOAN NO. 3400169949                (CONTINUED)                            PAGE 5
--------------------------------------------------------------------------------

hazardous waste or substance by any person on, under, about or from any of the
properties. (b) Borrower has no knowledge of, or reason to believe that there
has been (i) an unauthorized use, generation, manufacture, storage, treatment,
disposal, release, or threatened release of any hazardous waste or substance on,
under, about or from the properties by any prior owners or occupants of any of
THE PROPERTIES, OR (if) ANY ACTUAL OR THREATENED litigation or claims of any
kind by any person relating to such matters. (c) Neither Borrower nor any
tenant, contractor, agent or other authorized user of any of the properties
shall, in an unauthorized manner, use, generate, manufacture, store, treat,
dispose of, or release any hazardous waste or substance on, under, about or from
any of the properties; and any such activity shall be conducted in compliance
with all applicable federal, state, and local LAWS, regulations, and ordinances,
including without limitation those laws, regulations and ordinances described
above. As allowed by applicable law and upon reasonable prior notice lender may
enter upon the promises of Borrower to inspect the properties for compliance
with this section of the agreement. Any inspections or test made by Lender shall
be at Borrower's expense and for Lender's purposes only and shall not be
construed to create any responsibility or liability on the part of Lender to
Borrower or to any other person. The representations and warranties contained
herein are based on Borrower's due diligence in investigating the properties for
hazardous waste and hazardous substances. Borrower hereby (a) releases and
waives any future claims against Lender for indemnity or contribution in the
event Borrower becomes liable for cleanup or other costs under any such laws,
and (b) agrees to indemnify and hold harmless Lender against any and all claims,
losses, liabilities, damages, penalties, and expenses which Lender may directly
or indirectly sustain or suffer resulting from a breach of this section of the
Agreement or as a consequence of any unauthorized use, generation, manufacture,
storage, disposal, release or threatened release of a hazardous waste or
substance on the properties. The provisions of this section of the Agreement,
including the obligation to indemnify, shall survive the payment of the
indebtedness and the termination or expiration of this Agreement and shall not
be affected by Lender's acquisition of any interest in any of the properties,
whether by foreclosure or otherwise.

RIGHT OF SETOFF. Borrower grants to Lender a contractual security interest in,
and hereby assigns, conveys, delivers, pledges, and transfers to Lender all
Borrower's right, title and interest in and to, Borrower's accounts with Lender
(whether checking, savings, or some other account), including without limitation
all accounts held jointly with someone else and all accounts Borrower may open
in the future, excluding however all IRA and Keogh accounts, and all trust
accounts for which the grant of a security interest would be prohibited by law.
Borrower authorizes Lender, to the extent permitted by applicable law, to charge
or setoff all sums owing on the Indebtedness against any and all such accounts.

EVENTS OF DEFAULT. Each of the following shall constitute an Event of Default
under this Agreement:

       DEFAULT ON INDEBTEDNESS. Failure of Borrower to make any payment when due
       on the Loans.

       OTHER DEFAULTS. Failure of Borrower or any Grantor to comply with or to
       perform when due any other term, obligation, covenant or condition
       contained in this Agreement or in any of the Related Documents, or
       failure of Borrower to comply with or to perform any other term,
       obligation, covenant or condition contained in any other agreement
       between Lender and Borrower.

       ENVIRONMENTAL DEFAULT. Failure of any party to comply with or perform
       when due any term, obligation, covenant or condition contained in any
       environmental agreement executed in connection with any Loan.

       DEFAULT IN FAVOR OF THIRD PARTIES. Should Borrower or any Grantor default
       under any loan, extension of credit, security agreement, purchase or
       sales agreement, or any other agreement, in favor of any other creditor
       or person that may materially affect any of Borrower's property or
       Borrower's or any Grantor's ability to repay the Loans or perform their
       respective obligations under this Agreement or any of the Related
       Documents.

       FALSE STATEMENTS. Any warranty, representation or statement made or
       furnished to Lender by or on behalf of Borrower or any Grantor under this
       Agreement or the Related Documents is false or misleading in any material
       respect at the time made or furnished, or becomes false or misleading at
       any time thereafter.

       DEFECTIVE COLLATERALIZATION. This Agreement or any of the Related
       Documents ceases to be in full force and effect (including failure of any
       Security Agreement to create a valid and perfected Security Interest) at
       any time and for any reason.

       INSOLVENCY. The dissolution or termination of Borrower's existence as a
       going business, the insolvency of Borrower, the appointment of a receiver
       for any part of Borrower's property, any assignment for the benefit of
       creditors, any type of creditor workout, or the commencement of any
       proceeding under any bankruptcy or insolvency laws by or against
       Borrower.

       CREDITOR OR FORFEITURE PROCEEDINGS. Commencement of foreclosure or
       forfeiture proceedings, whether by judicial proceeding, self-help,
       repossession or any other method, by any creditor of Borrower, any
       creditor of any Grantor against any collateral securing the Indebtedness,
       or by any governmental agency. This includes a garnishment, attachment,
       or levy on or of any of Borrower's deposit accounts with Lender. However,
       this Event of Default shall not apply if there is a good faith dispute by
       Borrower or Grantor, as the case may be, as to the validity or
       reasonableness of the claim which is the basis of the creditor or
       forfeiture proceeding, and if Borrower or Grantor gives Lender written
       notice of the creditor or forfeiture proceeding and furnishes reserves or
       a surety bond for the creditor or forfeiture proceeding satisfactory to
       Lender.

       EVENTS AFFECTING GUARANTOR. Any of the preceding events occurs with
       respect to any Guarantor of any of the Indebtedness or any Guarantor dies
       or becomes incompetent, or revokes or disputes the validity of, or
       liability under, any Guaranty of the Indebtedness. Lender, at its option,
       may, but shall not be required to, permit the Guarantor's estate to
       assume unconditionally the obligations arising under the guaranty in a
       manner satisfactory to Lender, and, in doing so, cure the Event of
       Default.

       CHANGE IN OWNERSHIP. Any change in ownership of twenty-five percent (25%)
       or more of the common stock of Borrower.

       ADVERSE CHANGE. A material adverse change occurs in Borrower's financial
       condition, or Lender believes the prospect of payment or performance of
       the Indebtedness is impaired.

       INSECURITY. Lender, in good faith, deems itself insecure.

       RIGHT TO CURE. If any default, other than a Default on Indebtedness, is
       curable and if Borrower or Grantor, as the case may be, has not been
       given a notice of a similar default within the preceding twelve (12)
       months, it may be cured (and no Event of Default will have occurred) if
       Borrower or Grantor, as the case may be, after receiving written notice
       from Lender demanding cure of such default: (a) cures the default within
       fifteen (15) days; or (b) if the cure requires more than fifteen (15)
       days, immediately initiates steps which Lender deems in Lender's sole
       discretion to be sufficient to cure the default and thereafter continues
       and completes all reasonable and necessary steps sufficient to produce
       compliance as soon as reasonably practical.

<PAGE>   38

03-01-1999                  BUSINESS LOAN AGREEMENT
LOAN NO. 3400169949                (CONTINUED)                            PAGE 6
--------------------------------------------------------------------------------

EFFECT OF AN EVENT OF DEFAULT. If any Event of Default shall occur, except where
otherwise provided in this Agreement or the Related Documents, all commitments
and obligations of Lender under this Agreement or the Related Documents or any
other agreement Immediately will terminate and, at Lender's option, all
Indebtedness immediately will become due and payable, all without notice of any
kind to Borrower, except that in the case of an Event of Default of the type
described in the "Insolvency" subsection above, such acceleration shall be
automatic and not optional. In addition, Lender shall have all the rights and
remedies provided in the Related Documents or available at law, in equity, or
otherwise. Except as may be prohibited by applicable law, all of Lender's rights
and remedies shall be cumulative and may be exercised singularly or
concurrently. Election by Lender to pursue any remedy shall not exclude pursuit
of any other remedy, and an election to make expenditures or to take action to
perform an obligation of Borrower or of any Grantor shall not affect Lender's
right to declare a default and to exercise its rights and remedies.

MISCELLANEOUS PROVISIONS. The following miscellaneous provisions are a part of
this Agreement:

       AMENDMENTS. This Agreement, together with any Related Documents,
       constitutes the entire understanding and agreement of the parties as to
       the matters set forth in this Agreement. No alteration of or amendment to
       this Agreement shall be effective unless given in writing and signed by
       the party or parties sought to be charged or bound by the alteration or
       amendment.

       APPLICABLE LAW. THIS AGREEMENT HAS BEEN DELIVERED TO LENDER AND ACCEPTED
       BY LENDER IN THE STATE OF CALIFORNIA. IF THERE IS A LAWSUIT, BORROWER
       AGREES UPON LENDER'S REQUEST TO SUBMIT TO THE JURISDICTION OF THE COURTS
       OF NEVADA COUNTY, THE STATE OF CALIFORNIA. THIS AGREEMENT SHALL BE
       GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF
       CALIFORNIA.

       CAPTION HEADINGS. Caption headings in this Agreement are for convenience
       purposes only and are not to be used to interpret or define the
       provisions of this Agreement.

       MULTIPLE PARTIES; CORPORATE AUTHORITY. All obligations of Borrower under
       this Agreement shall be joint and several, and all references to Borrower
       shall mean each and every Borrower. This means that each of the persons
       signing below is responsible for all obligations in this Agreement.

       CONSENT TO LOAN PARTICIPATION. Borrower agrees and consents to Lender's
       sale or transfer, whether now or later, of one or more participation
       interests in the Loans to one or more purchasers, whether related or
       unrelated to Lender. Lender may provide, without any limitation
       whatsoever, to any one or more purchasers, or potential purchasers, any
       information or knowledge Lender may have about Borrower or about any
       other matter relating to the Loan, and Borrower hereby waives any rights
       to privacy it may have with respect to such matters. Borrower
       additionally waives any and all notices of sale of participation
       interests, as well as all notices of any repurchase of such participation
       interests. Borrower also agrees that the purchasers of any such
       participation interests will be considered as the absolute owners of such
       interests in the Loans and will have all the rights granted under the
       participation agreement or agreements governing the sale of such
       participation interests. Borrower further waives all rights of offset or
       counterclaim that it may have now or later against Lender or against any
       purchaser of such a participation interest and unconditionally agrees
       that either Lender or such purchaser may enforce Borrower's obligation
       under the Loans irrespective of the failure or insolvency of any holder
       of any interest in the Loans. Borrower further agrees that the purchaser
       of any such participation interests may enforce its interests
       irrespective of any personal claims or defenses that Borrower may have
       against Lender.

       COSTS AND EXPENSES. Borrower agrees to pay upon demand all of Lender's
       expenses, including without limitation attorneys' fees, incurred in
       connection with the preparation, execution, enforcement, modification and
       collection of this Agreement or in connection with the Loans made
       pursuant to this Agreement. Lender may pay someone else to help collect
       the Loans and to enforce this Agreement, and Borrower will pay that
       amount. This includes, subject to any limits under applicable law,
       Lender's attorneys' fees and Lender's legal expenses, whether or not
       there is a lawsuit, including attorneys' fees for bankruptcy proceedings
       (including efforts to modify or vacate any automatic stay or injunction),
       appeals, and any anticipated post-judgment collection services. Borrower
       also will pay any court costs, in addition to all other sums provided by
       law.

       NOTICES. All notices required to be given under this Agreement shall be
       given in writing, may be sent by telefacsimile (unless otherwise required
       by law), and shall be effective when actually delivered or when deposited
       with a nationally recognized overnight courier or deposited in the United
       States mail, first class, postage prepaid, addressed to the party to whom
       the notice is to be given at the address shown above. Any party may
       change its address for notices under this Agreement by giving formal
       written notice to the other parties, specifying that the purpose of the
       notice is to change the party's address. To the extent permitted by
       applicable law, if there is more than one Borrower, notice to any
       Borrower will constitute notice to all Borrowers. For notice purposes,
       Borrower will keep Lender informed at all times of Borrower's current
       address(es).

       SEVERABILITY. If a court of competent jurisdiction finds any provision of
       this Agreement to be invalid or unenforceable as to any person or
       circumstance, such finding shall not render that provision invalid or
       unenforceable as to any other persons or circumstances. If feasible, any
       such offending provision shall be deemed to be modified to be within the
       limits of enforceability or validity; however, if the offending provision
       cannot be so modified, it shall be stricken and all other provisions of
       this Agreement in all other respects shall remain valid and enforceable.

       SUBSIDIARIES AND AFFILIATES OF BORROWER. To the extent the context of any
       provisions of this Agreement makes it appropriate, including without
       limitation any representation, warranty or covenant, the word "Borrower"
       as used herein shall include all subsidiaries and affiliates of Borrower.
       Notwithstanding the foregoing however, under no circumstances shall this
       Agreement be construed to require Lender to make any Loan or other
       financial accommodation to any subsidiary or affiliate of Borrower.

       SUCCESSORS AND ASSIGNS. All covenants and agreements contained by or on
       behalf of Borrower shall bind its successors and assigns and shall inure
       to the benefit of Lender, its successors and assigns. Borrower shall not,
       however, have the right to assign its rights under this Agreement or any
       interest therein, without the prior written consent of Lender.

       SURVIVAL. All warranties, representations, and covenants made by Borrower
       in this Agreement or in any certificate or other instrument delivered by
       Borrower to Lender under this Agreement shall be considered to have been
       relied upon by Lender and will survive the making of the Loan and
       delivery to Lender of the Related Documents, regardless of any
       investigation made by Lender or on Lender's behalf.

       TIME IS OF THE ESSENCE. Time is of the essence in the performance of this
       Agreement.

       WAIVER. Lender shall not be deemed to have waived any rights under this
       Agreement unless such waiver is given in writing and signed by Lender. No
       delay or omission on the part of Lender in exercising any right shall
       operate as a waiver of such right or any other right. A waiver by Lender
       of a provision of this Agreement shall not prejudice or constitute a
       waiver of Lender's right otherwise to demand strict compliance with that
       provision or any other provision of this Agreement. No prior waiver by
       Lender, nor any course of dealing between Lender and Borrower, or between
       Lender and any Grantor, shall constitute a waiver of any of Lender's
       rights or of any obligations of Borrower or of any Grantor as to any
       future transactions.

<PAGE>   39

03-01-1999                  BUSINESS LOAN AGREEMENT
LOAN NO. 3400169949                (CONTINUED)                            PAGE 7
--------------------------------------------------------------------------------

       Whenever the consent of Lender is required under this Agreement, the
       granting of such consent by Lender in any instance shall not constitute
       continuing consent in subsequent instances where such consent is
       required, and in all cases such consent may be granted or withheld in the
       sole discretion of Lender.

BORROWER ACKNOWLEDGES HAVING READ ALL THE PROVISIONS OF THIS BUSINESS LOAN
AGREEMENT, AND BORROWER AGREES TO ITS TERMS. THIS AGREEMENT IS DATED AS OF MARCH
1, 1999.

BORROWER:

BIOSOURCE TECHNOLOGIES, INC.

By: Robert L. Erwin                         By: Michael D. Centron
    ---------------------------------           --------------------------------
    ROBERT L. ERWIN, CHAIRMAN OF THE BOARD      MICHAEL D. CENTRON, TREASURER.

--------------------------------------------------------------------------------

LENDER:

SierraWest Bank

By:
   ---------------------------------
   Authorized Officer

--------------------------------------------------------------------------------

<PAGE>   40
                         AGREEMENT TO PROVIDE INSURANCE

<TABLE>
<S>                 <C>            <C>             <C>          <C>     <C>         <C>       <C>      <C>
---------------------------------------------------------------------------------------------------------------
    PRINCIPAL        LOAN DATE      MATURITY       LOAN NO      CALL    COLLATERAL  ACCOUNT   OFFICER  INITIALS
  $1,900,424.00     03-01-1999     10-01-2001     3400169949     10                 111721      791
---------------------------------------------------------------------------------------------------------------
References in the shaded area are for Lender's use only and do not limit the applicability of this document to
any particular loan or item.
---------------------------------------------------------------------------------------------------------------
</TABLE>

BORROWER: BIOSOURCE TECHNOLOGIES, INC.           LENDER: SIERRAWEST BANK
          (TIN:  77-0154648)                             CENTRAL PACIFIC REGION
          3333 VACA VALLEY PARKWAY, SUITE 1000           1100 TEXAS ST.
          VACAVILLE, CA  95688-9412                      FAIRFIELD, CA  94533
--------------------------------------------------------------------------------

INSURANCE REQUIREMENTS. BIOSOURCE TECHNOLOGIES, INC. ("Grantor") understands
that insurance coverage is required in connection with the extending of a loan
or the providing of other financial accommodations to Grantor by Lender. These
requirements are set forth in the security documents. The following minimum
insurance coverages must be provided on the following described collateral (the
"Collateral"):

Collateral: ALL EQUIPMENT, CHATTEL PAPER, PERSONAL PROPERTY, ACCOUNTS
        RECEIVABLE, CONTRACT RIGHTS AND INTANGIBLES, NOW OR HEREAFTER ACQUIRED,
        BUT NOT INCLUDING ANY PATENTS, COPY RIGHTS OR TRADEMARKS OR SIMILAR
        INTELLECTUAL PROPERTY.
        TYPE. All risks, including fire, theft and liability.
        AMOUNT. $1,900,424.00.
        BASIS. Replacement value.
        ENDORSEMENTS. Lender's loss payable clause with stipulation that
        coverage will not be cancelled or diminished without a minimum of ten
        (10) days' prior written notice to Lender.
        DEDUCTIBLES. $1,000.00.

INSURANCE COMPANY. Grantor may obtain insurance from any insurance company
Grantor may choose that is reasonably acceptable to Lender. Grantor understands
that credit may not be denied solely because insurance was not purchased through
Lender.

INSURANCE MAILING ADDRESS. All documents and other materials relating to
insurance for this loan should be mailed, delivered or directed to the following
address:

    SIERRAWEST BANK, ATTENTION: S. POWELL
    P.O. BOX 61000
    10181 TRUCKEE TAHOE AIRPORT RD.
    TRUCKEE, CA 96160
    (530) 582-3864

FAILURE TO PROVIDE INSURANCE. Grantor agrees to deliver to Lender, ten (10) days
from the date of this Agreement, evidence of the required insurance as provided
above, with an effective date of March 1, 1999, or earlier.

AUTHORIZATION. For purposes of insurance coverage on the Collateral, Grantor
authorizes Lender to provide to any person (including any insurance agent or
company) all information Lender deems appropriate, whether regarding the
Collateral, the loan or other financial accommodations, or both.

GRANTOR ACKNOWLEDGES HAVING READ ALL THE PROVISIONS OF THIS AGREEMENT TO PROVIDE
INSURANCE AND AGREES TO ITS TERMS. THIS AGREEMENT IS DATED MARCH 1, 1999.

GRANTOR:

BIOSOURCE TECHNOLOGIES, INC.

By: Robert L. Erwin                         By: Michael D. Centron
    ---------------------------------           --------------------------------
    ROBERT L. ERWIN, CHAIRMAN OF THE BOARD      MICHAEL D. CENTRON, TREASURER.

--------------------------------------------------------------------------------

--------------------------------------------------------------------------------
                               FOR LENDER USE ONLY
                             INSURANCE VERIFICATION

DATE:                                                  PHONE:
     -----------------------------------                     -------------------

AGENT'S NAME:
             -------------------------------------------------------------------

INSURANCE COMPANY:
                  --------------------------------------------------------------

POLICY NUMBER:
              ------------------------------------------------------------------

EFFECTIVE DATES:
                ----------------------------------------------------------------

COMMENTS:
         -----------------------------------------------------------------------

--------------------------------------------------------------------------------

<PAGE>   41

                     DISBURSEMENT REQUEST AND AUTHORIZATION

<TABLE>
<S>                 <C>            <C>            <C>           <C>     <C>         <C>       <C>      <C>
---------------------------------------------------------------------------------------------------------------
    PRINCIPAL        LOAN DATE      MATURITY       LOAN NO      CALL    COLLATERAL  ACCOUNT   OFFICER  INITIALS
  $1,900,424.00     03-01-1999     10-01-2001     3400169949     10                 111721      791
---------------------------------------------------------------------------------------------------------------
References in the shaded area are for Lender's use only and do not limit the applicability of this document to
any particular loan or item.
---------------------------------------------------------------------------------------------------------------
</TABLE>

BORROWER: BIOSOURCE TECHNOLOGIES, INC.           LENDER: SIERRAWEST BANK
          (TIN:  77-0154648)                             CENTRAL PACIFIC REGION
          3333 VACA VALLEY PARKWAY, SUITE 1000           1100 TEXAS ST.
          VACAVILLE, CA  95688-9412                      FAIRFIELD, CA  94533
--------------------------------------------------------------------------------

LOAN TYPE. This is a Variable Rate (at Prime rate as published in the western
edition of the Wall Street Journal, making an initial rate of 7.750%),
Installment Loan to a Corporation for $1,900,424.00 due on October 1, 2001.

PRIMARY PURPOSE OF LOAN. The primary purpose of this loan is for:

         [ ]   Personal, Family, or Household Purposes or Personal Investment.

         [X]   Business (Including Real Estate Investment).

SPECIFIC PURPOSE. The specific purpose of this loan is: TERM OUT BALANCE AS OF
02/28/99 ON LINE OF CREDIT.

DISBURSEMENT INSTRUCTIONS. Borrower understands that no loan proceeds will be
disbursed until all of Lender's conditions for making the loan have been
satisfied. Please disburse the loan proceeds of $1,900,424.00 as follows:

<TABLE>
<S>                                                   <C>
        Amount paid on Borrower's account:                  $1,900,424.00
        $1,900,424.00 Payment on Loan #
        3400069949
                                                      --------------------------
        Note Principal:                                     $1,900,424.00
</TABLE>

FINANCIAL CONDITION. BY SIGNING THIS AUTHORIZATION, BORROWER REPRESENTS AND
WARRANTS TO LENDER THAT THE INFORMATION PROVIDED ABOVE IS TRUE AND CORRECT AND
THAT THERE HAS BEEN NO MATERIAL ADVERSE CHANGE IN BORROWER'S FINANCIAL CONDITION
AS DISCLOSED IN BORROWER'S MOST RECENT FINANCIAL STATEMENT TO LENDER. THIS
AUTHORIZATION IS DATED MARCH 1, 1999.

BORROWER:

BIOSOURCE TECHNOLOGIES, INC.

By: Robert L. Erwin                         By: Michael D. Centron
    ---------------------------------           --------------------------------
    ROBERT L. ERWIN, CHAIRMAN OF THE BOARD      MICHAEL D. CENTRON, TREASURER.

--------------------------------------------------------------------------------

<PAGE>   42
'
                         CORPORATE RESOLUTION TO BORROW

<TABLE>
<S>                  <C>            <C>            <C>           <C>     <C>         <C>       <C>      <C>
----------------------------------------------------------------------------------------------------------------
    PRINCIPAL         LOAN DATE      MATURITY       LOAN NO      CALL    COLLATERAL  ACCOUNT   OFFICER  INITIALS
  $1,900,424.00      03-01-1999     10-01-2001     3400169949     10                 111721      791
----------------------------------------------------------------------------------------------------------------
References in the shaded area are for Lender's use only and do not limit the applicability of this document to
any particular loan or item.
----------------------------------------------------------------------------------------------------------------
</TABLE>

<TABLE>
<S>             <C>                                              <C>        <C>
BORROWER:       BIOSOURCE TECHNOLOGIES, INC.                     LENDER:    SIERRAWEST BANK
                (TIN:  77-0154648)                                          CENTRAL PACIFIC REGION
                3333 VACA VALLEY PARKWAY, SUITE 1000                        1100 TEXAS ST.
                VACAVILLE, CA  95688-9412                                   FAIRFIELD, CA  94533

----------------------------------------------------------------------------------------------------------------
</TABLE>

I, THE UNDERSIGNED SECRETARY OR ASSISTANT SECRETARY OF BIOSOURCE TECHNOLOGIES,
INC. (THE "CORPORATION"), HEREBY CERTIFY THAT the Corporation is organized and
existing under and by virtue of the laws of the State of California as a
corporation for profit, with its principal office at 3333 VACA VALLEY PARKWAY,
SUITE 1000, VACAVILLE, CA 95688-9412, and is duly authorized to transact
business in the State of California.

I FURTHER CERTIFY that at a meeting of the Directors of the Corporation, duly
called and held on 0cf0di(IC / 4f / - 9 2 , at which a quorum was present and
voting, or by other duly authorized corporate action in lieu of a meeting, the
following resolutions were adopted:

BE IT RESOLVED, that any two (2) of the following named officers, employees, or
agents of this Corporation, whose actual signatures are shown below:

<TABLE>
<CAPTION>
NAMES                    POSITIONS                  ACTUAL SIGNATURES
-----                    ---------                  -----------------
<S>                      <C>                        <C>
ROBERT L. ERWIN          CHAIRMAN OF THE BOARD      x
                                                     ---------------------------
MICHAEL D. CENTRON       TREASURER                  x
                                                     ---------------------------
JOHN S. RAKITAN          SECRETARY                  x
                                                     ---------------------------
</TABLE>

acting for and on behalf of the Corporation and as its act and deed be, and they
hereby are, authorized and empowered:

       BORROW MONEY. To borrow from time to time from SierraWest Bank
       ("Lender"), on such terms as may be agreed upon between the Corporation
       and Lender, such sum or sums of money as in their judgment should be
       borrowed; however, not exceeding at any one time the amount of One
       Million NINE HUNDRED THOUSAND FOUR HUNDRED TWENTY FOUR & 00/100 DOLLARS
       ($1,900,424.00), in addition to such sum or sums of money as may be
       currently borrowed by the Corporation from Lender.

       EXECUTE NOTES. To execute and deliver to Lender the promissory note or
       notes, or other evidence of credit accommodations of the Corporation, on
       Lender's forms, at such rates of interest and on such terms as may be
       agreed upon, evidencing the sums of money so borrowed or any indebtedness
       of the Corporation to Lender, and also to execute and deliver to Lender
       one or more renewals, extensions, modifications, refinancings,
       consolidations, or substitutions for one or more of the notes, any
       portion of the notes, or any other evidence of credit accommodations.

       GRANT SECURITY. To mortgage, pledge, transfer, endorse, hypothecate, or
       otherwise encumber and deliver to Lender, as security for the payment of
       any loans or credit accommodations so obtained, any promissory notes so
       executed (including any amendments to or modifications, renewals, and
       extensions of such promissory notes), or any other or further
       indebtedness of the Corporation to Lender at any time owing, however the
       same may be evidenced, any property now or hereafter belonging to the
       Corporation or in which the Corporation now or hereafter may have an
       interest, including without limitation all real property and all personal
       property (tangible or intangible) of the Corporation. Such property may
       be mortgaged, pledged, transferred, endorsed, hypothecated, or encumbered
       at the time such loans are obtained or such indebtedness is incurred, or
       at any other time or times, and may be either in addition to or in lieu
       of any property theretofore mortgaged, pledged, transferred, endorsed,
       hypothecated, or encumbered.

       EXECUTE SECURITY DOCUMENTS. To execute and deliver to Lender the forms of
       mortgage, deed of trust, pledge agreement, hypothecation agreement, and
       other security agreements and financing statements which may be required
       by Lender, and which shall evidence the terms and conditions under and
       pursuant to which such liens and encumbrances, or any of them, are given;
       and also to execute and deliver to Lender any other written instruments,
       any chattel paper, or any other collateral, of any kind or nature, which
       Lender may deem necessary or proper in connection with or pertaining to
       the giving of the liens and encumbrances. Notwithstanding the foregoing,
       any one of the above authorized persons may execute, deliver, or record
       financing statements.

       NEGOTIATE ITEMS. To draw, endorse, and discount with Lender all drafts,
       trade acceptances, promissory notes, or other evidences of indebtedness
       payable to or belonging to the Corporation in which the Corporation may
       have an interest, and either to receive cash for the same or to cause
       such proceeds to be credited to the account of the Corporation with
       Lender, or to cause such other disposition of the proceeds derived
       therefrom as they may deem advisable.

       FURTHER ACTS. In the case of lines of credit,, to designate additional or
       alternate individuals as being authorized to request advances thereunder,
       and in all cases, to do and perform such other acts and things, to pay
       any and all fees and costs, and to execute and deliver such other
       documents and agreements as they may in their discretion deem reasonably
       necessary or proper in order to carry into effect the provisions of these
       Resolutions.

BE IT FURTHER RESOLVED, that any and all acts authorized pursuant to these
Resolutions and performed prior to the passage of these Resolutions are hereby
ratified and approved, that these Resolutions shall remain in full force and
affect and Lender may rely on these Resolutions until written notice of their
revocation shall have been delivered to and received by Lender. Any such notice
shall not affect any of the Corporation's agreements or commitments in effect at
the time notice is given.

<PAGE>   43

03-01-1999                  CORPORATE RESOLUTION TO BORROW
LOAN NO. 3400169949                  (CONTINUED)                          PAGE 2
--------------------------------------------------------------------------------

BE IT FURTHER RESOLVED, that the Corporation will notify Lender in writing at
Lender's address shown above (or such other addresses as Lender may designate
from time to time) prior to any (a) change in the name of the Corporation, (b)
change in the assumed business name(s) of the Corporation, (c) change in the
management of the Corporation, (d) change in the authorized signer(s), (e)
conversion of the Corporation to a new or different type of business entity, or
(f) change in any other aspect of the Corporation that directly or indirectly
relates to any agreements between the Corporation and Lender. No change in the
name of the Corporation will take effect until after Lender has been notified.

I FURTHER CERTIFY that the officers, employees, and agents named above are duly
elected, appointed, or employed by or for the Corporation, as the case may be,
and occupy the positions set opposite their respective names; that the foregoing
Resolutions now stand of record on the books of the Corporation; and that the
Resolutions are in full force and effect and have not been modified or revoked
in any manner whatsoever. The Corporation has no corporate seal, and therefore,
no seal is affixed to this certificate.

IN TESTIMONY WHEREOF, I HAVE HEREUNTO SET MY HAND ON MARCH 1, 1999 AND ATTEST
THAT THE SIGNATURES SET OPPOSITE THE NAMES LISTED ABOVE ARE THEIR genuine
signatures.

                                        CERTIFIED TO AND ATTESTED BY:

                                        x
                                         ---------------------------------------

                                        X
                                         ---------------------------------------

NOTE: In case the Secretary or other certifying officer is designated by the
foregoing resolutions as one of the signing officers, it is advisable to have
this certificate signed by a second Officer or Director of the Corporation.

--------------------------------------------------------------------------------

<PAGE>   44

03-01-1999                  COMMERCIAL SECURITY AGREEMENT
LOAN NO. 3400169949                  (CONTINUED)                          PAGE 3

--------------------------------------------------------------------------------

<TABLE>
<S>                 <C>            <C>            <C>           <C>     <C>         <C>       <C>      <C>
---------------------------------------------------------------------------------------------------------------
    PRINCIPAL        LOAN DATE      MATURITY       LOAN NO      CALL    COLLATERAL  ACCOUNT   OFFICER  INITIALS
  $5,000,000.00     11-30-1998     11-30-2001     3400069949     10                 111721      274
---------------------------------------------------------------------------------------------------------------
References in the shaded area are for Lender's use only and do not limit the applicability of this document to
any particular loan or item.
---------------------------------------------------------------------------------------------------------------
</TABLE>

<TABLE>
<S>             <C>                                              <C>        <C>
BORROWER:       BIOSOURCE TECHNOLOGIES, INC.                     LENDER:    SIERRAWEST BANK
                (TIN:  77-0154648)                                          CENTRAL PACIFIC REGION
                3333 VACA VALLEY PARKWAY, SUITE 1000                        1100 TEXAS ST.
                VACAVILLE, CA  95688-9412                                   FAIRFIELD, CA  94533
---------------------------------------------------------------------------------------------------------------
</TABLE>

THIS COMMERCIAL SECURITY AGREEMENT IS ENTERED INTO BETWEEN BIOSOURCE
TECHNOLOGIES, INC. (REFERRED TO BELOW AS "GRANTOR"); AND SIERRAWEST BANK
(REFERRED TO BELOW AS "LENDER"). FOR VALUABLE CONSIDERATION, GRANTOR GRANTS TO
LENDER A SECURITY INTEREST IN THE COLLATERAL TO SECURE THE INDEBTEDNESS AND
AGREES THAT LENDER SHALL HAVE THE RIGHTS STATED IN THIS AGREEMENT WITH RESPECT
TO THE COLLATERAL, IN ADDITION TO ALL OTHER RIGHTS WHICH LENDER MAY HAVE BY LAW.

DEFINITIONS. The following words shall have the following meanings when used in
this Agreement. Terms not otherwise defined in this Agreement shall have the
meanings attributed to such terms in the Uniform Commercial Code. All references
to dollar amounts shall mean amounts in lawful money of the United States of
America.

       AGREEMENT. The word "Agreement" means this Commercial Security Agreement,
       as this Commercial Security Agreement may be amended or modified from
       time to time, together with all exhibits and schedules attached to this
       Commercial Security Agreement from time to time.

       COLLATERAL. The word "Collateral" means the following described property
       of Grantor, whether now owned or hereafter acquired, whether now existing
       or hereafter arising, and wherever located:

              ALL EQUIPMENT, CHATTEL PAPER, PERSONAL PROPERTY, ACCOUNTS
              RECEIVABLE, CONTRACT RIGHTS AND INTANGIBLES, NOW OR HEREAFTER
              ACQUIRED, BUT NOT INCLUDING ANY PATENTS, COPY RIGHTS OR TRADEMARKS
              OR SIMILAR INTELLECTUAL PROPERTY

In addition, the word "Collateral" includes all the following, whether now owned
or hereafter acquired, whether now existing or hereafter arising, and wherever
located:

       (a) All attachments, accessions, accessories, tools, parts, supplies,
       increases, and additions to and all replacements of and substitutions for
       any property described above.

       (b) All products and produce of any of the property described ill this
       Collateral section.

       (c) All accounts, general intangibles, instruments, rents, monies,
       payments, and all other rights, arising out of a sale, lease, or other
       disposition of any of the property described ill this Collateral section.

       (d) All proceeds (including insurance proceeds) from the sale,
       destruction, loss, or other disposition of any of the property described
       in this Collateral section.

       (e) All records and data relating to any of the property described in
       this Collateral section, whether in the form of a writing, photograph,
       microfilm, microfiche, or electronic media, together with all of
       Grantor's right, title, and interest in and to all computer software
       required to utilize, create, maintain, and process any such records or
       data on electronic media.

       EVENT OF DEFAULT. The words "Event of Default" mean and include without
       limitation any of the Events of Default set forth below in the section
       titled "Events of Default."

       GRANTOR. The word "Grantor" means BIOSOURCE TECHNOLOGIES, INC., its
       successors and assigns

       GUARANTOR. The word "Guarantor" means and includes without limitation
       each and all of the guarantors, sureties, and accommodation parties in
       connection with the Indebtedness.

       INDEBTEDNESS. The word "Indebtedness" means the indebtedness evidenced by
       the Note, including all principal and interest, together with all other
       indebtedness and costs and expenses for which Grantor is responsible
       under this Agreement or under any of the Related Documents.

       LENDER. The word "Lender" means SierraWest Bank, its successors and
       assigns.

       NOTE. The word "Note" means the note or credit agreement dated November
       30, 1998, in the principal amount of $5,000,000.00 from BIOSOURCE
       TECHNOLOGIES, INC. to Lender, together with all renewals of, extensions
       of, modifications of, refinancings of, consolidations of and
       substitutions for the note or credit agreement.

       RELATED DOCUMENTS. The words "Related Documents" mean and include without
       limitation all promissory notes, credit agreements, loan agreements,
       environmental agreements, guaranties, security agreements, mortgages,
       deeds of trust, and all other instruments, agreements and documents,
       whether now or hereafter existing, executed in connection with the
       Indebtedness.

RIGHT OF SETOFF. Grantor hereby grants Lender a contractual security interest in
and hereby assigns, conveys, delivers, pledges, and transfers all of Grantor's
right, title and interest in and to Grantor's accounts with Lender (whether
checking, savings, or some other account), including all accounts held jointly
with someone else and all accounts Grantor may open in the future, excluding,
however, all IRA and Keogh accounts, and all trust accounts for which the grant
of a security interest would be prohibited by law. Grantor authorizes Lender, to
the extent permitted by applicable law, to charge or setoff all Indebtedness
against any and all such accounts.

OBLIGATIONS OF GRANTOR. Grantor warrants and covenants to Lender as follows:

<PAGE>   45

03-01-1999                  COMMERCIAL SECURITY AGREEMENT
LOAN NO. 3400169949                  (CONTINUED)                          PAGE 4

--------------------------------------------------------------------------------

       PERFECTION OF SECURITY INTEREST. Grantor agrees to execute such financing
       statements and to take whatever other actions are requested by Lender to
       perfect and continue Lender's security interest in the Collateral. Upon
       request of Lender, Grantor will deliver to Lender any and all of the
       documents evidencing or constituting the Collateral, and Grantor will
       note Lender's interest upon any and all chattel paper if not delivered to
       Lender for possession by Lender. Grantor hereby appoints Lender as its
       irrevocable attorney- in- fact for the purpose of executing any documents
       necessary to perfect or to continue the security interest granted in this
       Agreement. Lender may at any time, and without further authorization from
       Grantor, file a carbon, photographic or other reproduction of any
       financing statement or of this Agreement for use as a financing
       statement. Grantor will reimburse Lender for all expenses for the
       perfection and the continuation of the perfection of Lender's security
       interest in the Collateral. Grantor promptly will notify Lender before
       any change in Grantor's name including any change to the assumed business
       names of Grantor.

       NO VIOLATION. The execution and delivery of this Agreement will not
       violate any law or agreement governing Grantor or to which Grantor is a
       party, and its certificate or articles of incorporation and bylaws do not
       prohibit any term or condition of this Agreement.

       ENFORCEABILITY OF COLLATERAL. To the extent the Collateral consists of
       accounts, chattel paper, or general intangibles, the Collateral is
       enforceable in accordance with its terms, is genuine, and complies with
       applicable laws concerning form, content and manner of preparation and
       execution, and all persons appearing to be obligated on the Collateral
       have authority and capacity to contract and are in fact obligated as they
       appear to be on the Collateral.

       LOCATION OF THE COLLATERAL. Grantor, upon request of Lender, will deliver
       to Lender in form satisfactory to Lender a schedule of real properties
       and Collateral locations relating to Grantor's operations, including
       without limitation the following: (a) all real property owned or being
       purchased by Grantor; (b) all real property being rented or leased by
       Grantor; (c) all storage facilities owned, rented, leased, or being used
       by Grantor; and (d) all other properties where Collateral is or may be
       located. Except in the ordinary course of its business, Grantor shall not
       remove the Collateral from its existing locations without the prior
       written consent of Lender.

       REMOVAL OF COLLATERAL. Grantor shall keep the Collateral (or to the
       extent the Collateral consists of intangible property such as accounts,
       the records concerning the Collateral) at Grantor's address shown above,
       or at such other locations as are acceptable to Lender. Except in the
       ordinary course of its business, including the sales of inventory,
       Grantor shall not remove the Collateral from its existing locations
       without the prior written consent of Lender. To the extent that the
       Collateral consists of vehicles, or other titled property, Grantor shall
       not take or permit any action which would require application for
       certificates of title for the vehicles outside the State of California,
       without the prior written consent of Lender,

       TRANSACTIONS INVOLVING COLLATERAL. Except for inventory sold or accounts
       collected in the ordinary course of Grantor's business, Grantor shall not
       sell, offer to sell, or otherwise transfer or dispose of the Collateral.
       While Grantor is not in default under this AGREEMENT, GRANTOR MAY sell
       inventory, but only in the ordinary course of its business and only to
       buyers who qualify as a buyer in THE ORDINARY COURSE OF BUSINESS. A sale
       in the ordinary course of Grantor's business does not include a transfer
       in partial or total satisfaction of a debt or any bulk sale. Grantor
       shall not pledge, mortgage, encumber or otherwise permit the Collateral
       to be subject to any lien, security interest, encumbrance, or charge,
       other than the security interest provided for in this Agreement, without
       the prior written consent of Lender. This includes security interests
       even if junior in right reason) shall be held in trust for Lender and
       shall not be commingled with any other funds; provided however, this
       requirement shall not constitute consent by Lender to any sale or other
       disposition. Upon receipt, Grantor shall immediately deliver any such
       proceeds to Lender.

       TITLE. Grantor represents and warrants to Lender that it holds good and
       marketable title to the Collateral, free and clear of all liens arid
       encumbrances except for the lien of this Agreement. No financing
       statement covering any of the Collateral is on file in any public office
       other than those which reflect the security interest created by this
       Agreement or to which Lender has specifically consented. Grantor shall
       defend Lender's rights in the Collateral against the claims and demands
       of all other persons.

       COLLATERAL SCHEDULES AND LOCATIONS. Insofar as the Collateral consists of
       inventory, Grantor shall deliver to Lender, as often as Lender shall
       require, such lists, descriptions, and designations of such Collateral as
       Lender may require to identify the nature, extent, and location of such
       Collateral. Such information shall be submitted for Grantor and each of
       its subsidiaries or related companies.

       MAINTENANCE ARID INSPECTION OF COLLATERAL. Grantor shall maintain all
       tangible Collateral in good condition and repair. Grantor will not commit
       or permit damage to or destruction of the Collateral or any part of the
       Collateral. Lender and its designated representatives and agents shall
       have the right at all reasonable times to examine, inspect, and audit the
       Collateral wherever located. Grantor shall immediately notify Lender of
       all cases involving the return, rejection, repossession, loss or damage
       of or to any Collateral; of any request for credit or adjustment or of
       any other dispute arising with respect to the Collateral: and generally
       of all happenings and events affecting the Collateral or the value or the
       amount of the Collateral.

       TAXES, ASSESSMENTS AND LIENS. Grantor will pay when due all taxes,
       assessments and liens upon the Collateral, its use or operation, upon
       this Agreement, upon any promissory note or notes evidencing the
       Indebtedness, or upon any of the other Related Documents. Grantor may
       withhold any such payment or may elect to contest any lien if Grantor is
       in good faith conducting an appropriate proceeding to contest the
       obligation to pay and so long as Lender's interest in the Collateral is
       not jeopardized in Lender's sole opinion. If the Collateral is subjected
       to a lien which is not discharged within fifteen (15) days, Grantor shall
       deposit with Lender cash, a sufficient corporate surety bond or other
       security satisfactory to Lender in an amount adequate to provide for the
       discharge of the lien plus any interest, costs, attorneys' fees or other
       charges that could accrue as a result of foreclosure or sale of the
       Collateral. In any contest Grantor shall defend itself and Lender and
       shall satisfy any final adverse judgment before enforcement against the
       Collateral. Grantor shall name Lender as an additional obligee under any
       surety bond furnished in the contest proceedings.

       COMPLIANCE WITH GOVERNMENTAL REQUIREMENTS. Grantor shall comply promptly
       with all laws, ordinances, rules and regulations of all governmental
       authorities, including without limitation all environmental laws,
       ordinances, rules and regulations, now or hereafter in effect, applicable
       to the ownership, production, disposition, or use of the Collateral.
       Grantor may contest in good faith any such law, ordinance or regulation
       and withhold compliance during any proceeding, including appropriate
       appeals, so long as Lender's interest in the Collateral, in Lender's
       opinion, is not jeopardized.

       MAINTENANCE OF CASUALTY INSURANCE. Grantor shall procure and maintain all
       risks insurance, including without limitation fire, theft and liability
       coverage together with such other insurance as Lender may require with
       respect to the Collateral, in form, amounts, coverages and basis
       reasonably acceptable to Lender and issued by a company or companies
       reasonably acceptable to Lender. Grantor, upon request of Lender, will
       deliver to Lender from time to time the policies or certificates of
       insurance in form satisfactory to Lender, including stipulations that
       coverages will not be cancelled or diminished without at least ten (10)
       days' prior written notice to Lender and not including any disclaimer of
       the insurer's liability for failure to give such a notice. Each insurance
       policy also shall include an endorsement providing that coverage in favor
       of Lender will not be

<PAGE>   46
03-01-1999                  COMMERCIAL SECURITY AGREEMENT
LOAN NO. 3400169949                  (CONTINUED)                          PAGE 5

--------------------------------------------------------------------------------

       impaired in any way by any act, omission or default of Grantor or any
       other person. In connection with all policies covering assets in which
       Lender holds or is offered a security interest, Grantor will provide
       Lender with such loss payable or other endorsements as Lender may
       require. In no event shall the insurance be in an amount less than the
       amount agreed upon in the Agreement to Provide Insurance. It Grantor at
       any time fails to obtain or maintain any insurance as required under this
       Agreement, Lender may (but shall not be obligated to) obtain such
       insurance as Lender deems appropriate, including if it so chooses "single
       interest insurance," which will cover only Lender's interest in the
       Collateral.

       APPLICATION OF INSURANCE PROCEEDS. Grantor shall promptly notify Lender
       of any loss or damage to the Collateral. Lender may make proof of loss if
       Grantor fails to do so within fifteen (15) days of the casualty. All
       proceeds of any insurance on the Collateral, including accrued proceeds
       thereon, shall be held by Lender as part of the Collateral. If Lender
       consents to repair or replacement of the damaged or destroyed Collateral,
       Lender shall, upon satisfactory proof of expenditure, pay or reimburse
       Grantor from the proceeds for the reasonable cost of repair or
       restoration. If Lender does not consent to repair or replacement of the
       Collateral, Lender shall retain a sufficient amount of the proceeds to
       pay all of the Indebtedness, and shall pay the balance to Grantor. Any
       proceeds which have not been disbursed within six (6) months after their
       receipt and which Grantor has not committed to the repair or restoration
       of the Collateral shall be used to prepay the Indebtedness.

       INSURANCE RESERVES. Lender may require Grantor to maintain with Lender
       reserves for payment of insurance premiums, which reserves shall be
       created by monthly payments from Grantor of a sum estimated by Lender to
       be sufficient to produce, at least fifteen (15) days before the premium
       due date, amounts at least equal to the insurance premiums to be paid. If
       fifteen (15) days before payment is due, the reserve funds are
       insufficient, Grantor shall upon demand pay any deficiency to Lender. The
       reserve funds shall be held by Lender as a general deposit and shall
       constitute a non- interest-bearing account which Lender may satisfy by
       payment of the insurance premiums required to be paid by Grantor as they
       become due. Lender does not hold the reserve funds in trust for Grantor,
       and Lender is not the agent of Grantor for payment of the insurance
       premiums required to be paid by Grantor. The responsibility for the
       payment of premiums shall remain Grantor's sole responsibility.

       INSURANCE REPORTS. Grantor, upon request of Lender, shall furnish to
       Lender reports on each existing policy of insurance showing such
       information as Lender may reasonably request including the following: (a)
       the name of the insurer; (b) the risks insured; (c) the amount of the
       policy; (d) the property insured; (e) the then current value on the basis
       of which insurance has been obtained and the manner of determining that
       value; and (f) the expiration date of the policy. In addition, Grantor
       shall upon request by Lender (however not more often than annually) have
       an independent appraiser satisfactory to Lender determine, as applicable,
       the cash value or replacement cost of the Collateral.

GRANTOR'S RIGHT TO POSSESSION. Until default, Grantor may have possession of the
tangible personal property and beneficial use of all the Collateral and may use
it in any lawful manner not inconsistent with this Agreement or the Related
Documents, provided that Grantor's right to possession and beneficial use shall
not apply to any Collateral where possession of the Collateral by Lender is
required by law to perfect Lender's security interest in such Collateral. If
Lender at any time has possession of any Collateral, whether before or after an
Event of Default, Lender shall be deemed to have exercised reasonable care in
the custody and preservation of the Collateral if Lender takes such action for
that purpose as Grantor shall request or as Lender, in Lender's sole discretion,
shall deem appropriate under the circumstances, but failure to honor any request
by Grantor shall not of itself be deemed to be a failure to exercise reasonable
care. Lender shall not be required to take any steps necessary to preserve any
rights in the Collateral against prior parties, nor to protect, preserve or
maintain any security interest given to secure the Indebtedness.

EXPENDITURES BY LENDER. If not discharged or paid when due, Lender may (but
shall not be obligated to) discharge or pay any amounts required to be
discharged or paid by Grantor under this Agreement, including without limitation
all taxes, liens, security interests, encumbrances, and other claims, at any
time levied or placed on the Collateral. Lender also may (but shall not be
obligated to) pay all costs for insuring, maintaining and preserving the
Collateral. All such expenditures incurred or paid by Lender for such purposes
will then bear interest at the rate charged under the Note from the date
incurred or paid by Lender to the date of repayment by Grantor. All such
expenses shall become a part of the Indebtedness and, at Lender's option, will
(a) be payable on demand, (b) be added to the balance of the Note and be
apportioned among and be payable with any installment payments to become due
during either (I) the term of any applicable insurance policy or (ii) the
remaining term of the Note, or (c) be treated as a balloon payment which will be
due and payable at the Note's maturity. This Agreement also will secure payment
of these amounts. Such right shall be in addition to all other rights and
remedies to which Lender may be entitled upon the occurrence of an Event of
Default.

EVENTS OF DEFAULT. Each of the following shall constitute an Event of Default
under this Agreement:

       DEFAULT ON INDEBTEDNESS. Failure of Grantor to make any payment when due
       on the Indebtedness.

       ENVIRONMENTAL DEFAULT. Failure of any party to comply with or perform
       when due any term, obligation, covenant or condition contained in any
       environmental agreement executed in connection with any Loan.

       OTHER DEFAULTS. Failure of Grantor to comply with or to perform any other
       term, obligation, covenant or condition contained in this Agreement or in
       any of the Related Documents or in any other agreement between Lender and
       Grantor.

       DEFAULT IN FAVOR OF THIRD PARTIES. Should Borrower or any Grantor default
       under any loan, extension of credit, security agreement, purchase or
       sales agreement, or any other agreement, in favor of any other creditor
       or person that may materially affect any of Borrower's property or
       Borrower's or any Grantor's ability to repay the Loans or perform their
       respective obligations under this Agreement or any of the Related
       Documents.

       FALSE STATEMENTS. Any warranty, representation or statement made or
       furnished to Lender by or on behalf of Grantor under this Agreement, the
       Note or the Related Documents is false or misleading in any material
       respect, either now or at the time made or furnished.

       DEFECTIVE COLLATERALIZATION. This Agreement or any of the Related
       Documents ceases to be in full force and effect (including failure of any
       collateral documents to create a valid and perfected security interest or
       lien) at any time and for any reason.

       INSOLVENCY. The dissolution or termination of Grantor's existence as a
       going business, the insolvency of Grantor, the appointment of a receiver
       for any part of Grantor's property, any assignment for the benefit of
       creditors, any type of creditor workout or the commencement of any
       proceeding under any bankruptcy or insolvency laws by or against Grantor.

       CREDITOR OR FORFEITURE PROCEEDINGS. Commencement of foreclosure or
       forfeiture proceedings, whether by judicial proceeding, self-help,
       repossession or any other method, by any creditor of Grantor or by any
       governmental agency against the Collateral or any other collateral
       securing the Indebtedness. This includes a garnishment of any of
       Grantor's deposit accounts with Lender. However, this Event of Default
       shall not apply if there is a good faith dispute by Grantor as to the
       validity or reasonableness of the claim which is the basis of the
       creditor or forfeiture proceeding

<PAGE>   47

03-01-1999                  COMMERCIAL SECURITY AGREEMENT
LOAN NO. 3400169949                  (CONTINUED)                          PAGE 6

--------------------------------------------------------------------------------

       and if Grantor gives Lender written notice of the creditor or forfeiture
       proceeding and deposits with Lender monies or a surety bond for the
       creditor or forfeiture proceeding, in an amount determined by Lender, in
       its sole discretion, as being an adequate reserve or bond for the
       dispute.

       EVENTS AFFECTING GUARANTOR. Any of the preceding events occurs with
       respect to any Guarantor of any of the Indebtedness or such Guarantor
       dies or becomes incompetent. Lender, at its option, may, but shall not be
       required to, permit the Guarantor's estate to assume unconditionally the
       obligations arising under the guaranty in a manner satisfactory to
       Lender, and, in doing so, cure the Event of Default.

       ADVERSE CHANGE. A material adverse change occurs in Grantor's financial
       condition, or Lender believes the prospect of payment or performance of
       the Indebtedness is impaired.

       RIGHT TO CURE. If any default, other than a Default on Indebtedness, is
       curable and if Grantor has not been given a prior notice of a breach of
       the same provision of this Agreement, it may be cured (and no Event of
       Default will have occurred) if Grantor, after Lender sends written notice
       demanding cure of such default, (a) cures the default within fifteen (15)
       days; or (b), if the cure requires more than fifteen (15) days,
       immediately initiates steps which Lender deems in Lender's sole
       discretion to be sufficient to cure the default and thereafter continues
       and completes all reasonable and necessary steps sufficient to produce
       compliance as soon as reasonably practical.

RIGHTS AND REMEDIES ON DEFAULT. If an Event of Default occurs under this
Agreement, at any time thereafter, Lender shall have all the rights of a secured
party under the California Uniform Commercial Code. In addition and without
limitation, Lender may exercise any one or more of the following rights and
remedies:

       ACCELERATE INDEBTEDNESS. Lender may declare the entire Indebtedness,
       including any prepayment penalty which Grantor would be required to pay,
       immediately due and payable, without notice.

       ASSEMBLE COLLATERAL. Lender may require Grantor to deliver to Lender all
       or any portion of the Collateral and any and all certificates of title
       and other documents relating to the Collateral. Lender may require
       Grantor to assemble the Collateral and make it available to Lender at a
       place to be designated by Lender. Lender also shall have full power to
       enter upon the property of Grantor to take possession of and remove the
       Collateral. If the Collateral contains other goods not covered by this
       Agreement at the time of repossession, Grantor agrees Lender may take
       such other goods, provided that Lender makes reasonable efforts to return
       them to Grantor after repossession.

       SELL THE COLLATERAL. Lender shall have full power to sell, lease,
       transfer, or otherwise deal with the Collateral or proceeds thereof in
       its own name or that of Grantor. Lender may sell the Collateral at public
       auction or private sale. Unless the Collateral threatens to decline
       speedily in value or is of a type customarily sold on a recognized
       market, Lender will give Grantor reasonable notice of the time after
       which any private sale or any other intended disposition of the
       Collateral is to be made, The requirements of reasonable notice shall be
       met if such notice is given at least ten (10) days, or such lesser time
       as required by state law, before the time of the sale or disposition. All
       expenses relating to the disposition of the Collateral, including without
       limitation the expenses of retaking, holding, insuring, preparing for
       sale and selling the Collateral, shall become a part of the Indebtedness
       secured by this Agreement and shall be payable on demand, with interest
       at the Note rate from date of expenditure until repaid.

       APPOINT RECEIVER. To the extent permitted by applicable law, Lender shall
       have the following rights and remedies regarding the appointment of a
       receiver: (a) Lender may have a receiver appointed as a matter of right,
       (b) the receiver may be an employee of Lender and may serve without bond,
       and (c) all fees of the receiver and his or her attorney shall become
       part of the indebtedness secured by this Agreement and shall be payable
       on demand, with interest at the Note rate from date of expenditure until
       repaid.

       COLLECT REVENUES, APPLY ACCOUNTS. Lender, either itself or through a
       receiver, may collect the payments, rents, income, and revenues from the
       Collateral. Lender may at any time in its discretion transfer any
       Collateral into its own name or that of its nominee and receive the
       payments, rents, income, and revenues therefrom and hold the same as
       security for the Indebtedness or apply it to payment of the Indebtedness
       in such order of preference as Lender may determine. Insofar as the
       Collateral consists of accounts, general intangibles, insurance policies,
       instruments, chattel paper, choses in action, or similar property, Lender
       may demand, collect, receipt for, settle, compromise, adjust, sue for,
       foreclose, or realize on the Collateral as Lender may determine, whether
       or not Indebtedness or Collateral is then due. For these purposes, Lender
       may, on behalf of and in the name of Grantor, receive, open and dispose
       of mail addressed to Grantor; change any address to which mail and
       payments are to be sent; and endorse notes, checks, drafts, money orders,
       documents of title, instruments and items pertaining to payment,
       shipment, or storage of any Collateral. To facilitate collection, Lender
       may notify account debtors and obligors on any Collateral to make
       payments directly to Lender.

       OBTAIN DEFICIENCY. If Lender chooses to sell any or all of the
       Collateral, Lender may obtain a judgment against Grantor for any
       deficiency remaining on the Indebtedness due to Lender after application
       of all amounts received from the exercise of the rights provided in this
       Agreement. Grantor shall be liable for a deficiency even if the
       transaction described in this subsection is a sale of accounts or chattel
       paper.

       OTHER RIGHTS AND REMEDIES. Lender shall have all the rights and remedies
       of a secured creditor under the provisions of the Uniform Commercial
       Code, as may be amended from time to time. In addition, Lender shall have
       and may exercise any or all other rights and remedies it may have
       available at law, in equity, or otherwise.

       CUMULATIVE REMEDIES. All of Lender's rights and remedies, whether
       evidenced by this Agreement or the Related Documents or by any other
       writing, shall be cumulative and may be exercised singularly or
       concurrently. Election by Lender to pursue any remedy shall not exclude
       pursuit of any other remedy, and an election to make expenditures or to
       take action to perform an obligation of Grantor under this Agreement,
       after Grantor's failure to perform, shall not affect Lender's right to
       declare a default and to exercise its remedies.

MISCELLANEOUS PROVISIONS. The following miscellaneous provisions are a part of
this Agreement:

       AMENDMENTS. This Agreement, together with any Related Documents,
       constitutes the entire understanding and agreement of the parties as to
       the matters set forth in this Agreement. No alteration of or amendment to
       this Agreement shall be effective unless given in writing and signed by
       the party or parties sought to be charged or bound by the alteration or
       amendment.

       APPLICABLE LAW. This Agreement has been delivered to Lender and accepted
       by Lender in the State of California. If there is a lawsuit, Grantor
       agrees upon Lender's request to submit to the jurisdiction of the courts
       of NEVADA County, the State of California. This Agreement shall be
       governed by and construed in accordance with the laws of the State of
       California.

<PAGE>   48

03-01-1999                  COMMERCIAL SECURITY AGREEMENT
LOAN NO. 3400169949                  (CONTINUED)                          PAGE 7

--------------------------------------------------------------------------------

       ATTORNEYS' FEES; EXPENSES. Grantor agrees to pay upon demand all of
       Lender's costs and expenses, including attorneys' fees and Lender's legal
       expenses, incurred in connection with the enforcement of this Agreement.
       Lender may pay someone else to help enforce this Agreement, and Grantor
       shall pay the costs and expenses of such enforcement. Costs and expenses
       include Lender's attorneys' fees and legal expenses whether or not there
       is a lawsuit, including attorneys' fees and legal expenses for bankruptcy
       proceedings (and including efforts to modify or vacate any automatic stay
       or injunction), appeals, and any anticipated post-judgment collection
       services. Grantor also shall pay all court costs and such additional fees
       as may be directed by the court.

       CAPTION HEADINGS. Caption headings in this Agreement are for convenience
       purposes only and are not to be used to interpret or define the
       provisions of this Agreement.

       MULTIPLE PARTIES; CORPORATE AUTHORITY. All obligations of Grantor under
       this Agreement shall be joint and several, and all references to Grantor
       shall mean each and every Grantor. This means that each of the persons
       signing below is responsible for all obligations in this Agreement.

       NOTICES. All notices required to be given under this Agreement shall be
       given in writing, may be sent by telefacsimile (unless otherwise required
       by law), and shall be effective when actually delivered or when deposited
       with a nationally recognized overnight courier or deposited in the United
       States mail, first class, postage prepaid, addressed to the party to whom
       the notice is to be given at the address shown above. Any party may
       change its address for notices under this Agreement by giving formal
       written notice to the other parties, specifying that the purpose of the
       notice is to change the party's address. To the extent permitted by
       applicable law, if there is more than one Grantor, notice to any Grantor
       will constitute notice to all Grantors. For notice purposes, Grantor will
       keep Lender informed at all times of Grantor's current address(es),

       POWER OF ATTORNEY. Grantor hereby appoints Lender as its true and lawful
       attorney- in- fact, irrevocably, with full power of substitution to do
       the following: (a) to demand, collect, receive, receipt for, sue and
       recover all sums of money or other property which may now or hereafter
       become due, owing or payable from the Collateral; (b) to execute, sign
       and endorse any and all claims, instruments, receipts, checks, drafts or
       warrants issued in payment for the Collateral; (c) to settle or
       compromise any and all claims arising under the Collateral, and, in the
       place and stead of Grantor, to execute and deliver its release and
       settlement for the claim; and (d) to file any claim or claims or to take
       any action or institute or take part in any proceedings, either in its
       own name or in the name of Grantor, or otherwise, which in the discretion
       of Lender may seem to be necessary or advisable. This power is given as
       security for the Indebtedness, and the authority hereby conferred is and
       shall be irrevocable and shall remain in full force and effect until
       renounced by Lender.

       ??????? [Draft cut-off last line] Indebtedness and, at Lender's option,
       shall be payable by Borrower as provided above in the "EXPENDITURES BY
       LENDER" paragraph.

       SEVERABILITY. If a court of competent jurisdiction finds any provision of
       this Agreement to be invalid or unenforceable as to any person or
       circumstance, such finding shall not render that provision invalid or
       unenforceable as to any other persons or circumstances. If feasible, any
       such offending provision shall be deemed to be modified to be within the
       limits of enforceability or validity; however, if the offending provision
       cannot be so modified, it shall be stricken and all other provisions of
       this Agreement in all other respects shall remain valid and enforceable.

       SUCCESSOR INTERESTS. Subject to the limitations set forth above on
       transfer of the Collateral, this Agreement shall be binding upon and
       inure to the benefit of the parties, their successors and assigns.

       WAIVER. Lender shall not be deemed to have waived any rights under this
       Agreement unless such waiver is given in writing and signed by Lender. No
       delay or omission on the part of Lender in exercising any right shall
       operate as a waiver of such right or any other right. A waiver by Lender
       of a provision of this Agreement shall not prejudice or constitute a
       waiver of Lender's right otherwise to demand strict compliance with that
       provision or any other provision of this Agreement. No prior waiver by
       Lender, nor any course of dealing between Lender and Grantor, shall
       constitute a waiver of any of Lender's rights or of any of Grantor's
       obligations as to any future transactions. Whenever the consent of Lender
       is required under this Agreement, the granting of such consent by Lender
       in any instance shall not constitute continuing consent to subsequent
       instances where such consent is required and in all cases such consent
       may be granted or withheld in the sole discretion of Lender.

       WAIVER OF CO-OBLIGOR'S RIGHTS. If more than one person is obligated for
       the Indebtedness, Borrower irrevocably waives, disclaims and relinquishes
       all claims against such other person which Borrower has or would
       otherwise have by virtue of payment of the Indebtedness or any part
       thereof, specifically including but not limited to all rights of
       indemnity, contribution or exoneration.

GRANTOR ACKNOWLEDGES HAVING READ ALL THE PROVISIONS OF THIS COMMERCIAL SECURITY
AGREEMENT, AND GRANTOR AGREES TO ITS TERMS. THIS AGREEMENT IS DATED
NOVEMBER 30,1998,

GRANTOR:

BIOSOURCE TECHNOLOGIES, INC.

By:  Robert L. Erwin                          By: Michael D. Centron
   -----------------------------------------    --------------------------------
     ROBERT L. ERWIN, CHAIRMAN OF THE BOARD       MICHAEL D. CENTRON, TREASURER.

--------------------------------------------------------------------------------

<PAGE>   49
                             BUSINESS LOAN AGREEMENT

<TABLE>
<CAPTION>
    PRINCIPAL         LOAN DATE       MATURITY       LOAN NO     CALL   COLLATERAL  ACCOUNT   OFFICER  INITIALS
<S>                  <C>             <C>           <C>           <C>    <C>         <C>       <C>      <C>
  $1,503,985.26      06-07-1999      10-01-2001    3400369949     11                111721      791
</TABLE>

  References in the shaded area are for Lender's use only and do not limit the
         applicability of this document to any particular loan or item.

<TABLE>
<S>                                              <C>
BORROWER: BIOSOURCE TECHNOLOGIES, INC.           LENDER: SIERRAWEST BANK
          (TIN: 77-0154648)                              CENTRAL PACIFIC REGION
          3333 VACA VALLEY PARKWAY, SUITE 1000           1100 TEXAS ST
          VACAVILLE, CA 95688-9412                       FAIRFIELD, CA 94533
</TABLE>

THIS BUSINESS LOAN AGREEMENT between BIOSOURCE TECHNOLOGIES, INC. ("Borrower")
and SierraWest Bank ("Lender") is made and executed on the following terms and
conditions. Borrower has received prior commercial loans from Lender or has
applied to Lender for a commercial loan or loans and other financial
accommodations, Including those which may be described on any exhibit or
schedule attached to this Agreement. All such loans and financial
accommodations, together with all future loans and financial accommodations from
Lender to Borrower, are referred to in this Agreement individually as the "Loan"
and collectively as the "Loans." Borrower understands and agrees that: (a) in
granting, renewing, or extending any Loan, Lender Is relying upon Borrower's
representations, warranties, and agreements, as set forth In this Agreement; (b)
the granting, renewing, or extending of any Loan by Lender at all times shall be
subject to Lender's sole judgment and discretion; and (c) all such Loans shall
be and shall remain subject to the following terms and conditions of this
Agreement.

TERM. This Agreement shall be effective as of June 7, 1999, and shall continue
thereafter until all Indebtedness of Borrower to Lender has been performed in
full and the parties terminate this Agreement in writing.

DEFINITIONS. The following words shall have the following meanings when used in
this Agreement. Terms not otherwise defined in this Agreement shall have the
meanings attributed to such terms in the Uniform Commercial Code. All references
to dollar amounts shall mean amounts in lawful money of the United States of
America.

    AGREEMENT. The word "Agreement" means this Business Loan Agreement, as this
    Business Loan Agreement may be amended or modified from time to time,
    together with all exhibits and schedules attached to this Business Loan
    Agreement from time to time.

    BORROWER. The word "Borrower" means BIOSOURCE TECHNOLOGIES, INC.. The word
    "Borrower" also includes, as applicable, all subsidiaries and affiliates of
    Borrower as provided below in the paragraph titled "Subsidiaries and
    Affiliates."

    COLLATERAL. The word "Collateral" means and includes without limitation all
    property and assets granted as collateral security for a Loan, whether real
    or personal property, whether granted directly or indirectly, whether
    granted now or in the future, and whether granted in the form of a security
    interest, mortgage, deed of trust, assignment, pledge, chattel mortgage,
    chattel trust, factor's lien, equipment trust, conditional sale, trust
    receipt, lien, charge, lien or title retention contract, lease or
    consignment intended as a security device, or any other security or lien
    interest whatsoever, whether created by law, contract, or otherwise.

    ERISA. The word "ERISA" means the Employee Retirement Income Security Act of
    1974, as amended.

    EVENT OF DEFAULT. The words "Event of Default" mean and include without
    limitation any of the Events of Default set forth below in the section
    titled "EVENTS OF DEFAULT."

    GRANTOR. The word "Grantor" means and includes without limitation each and
    all of the persons or entities granting a Security Interest in any
    Collateral for the Indebtedness, including without limitation all Borrowers
    granting such a Security Interest.

    GUARANTOR. The word "Guarantor" means and includes without limitation each
    and all of the guarantors, sureties, and accommodation parties in connection
    with any Indebtedness.

    INDEBTEDNESS. The word "Indebtedness" means and includes without limitation
    all Loans, together with all other obligations, debts and liabilities of
    Borrower to Lender, or any one or more of them, as well as all claims by
    Lender against Borrower, or any one or more of them; whether now or
    hereafter existing, voluntary or involuntary, due or not due, absolute or
    contingent, liquidated or unliquidated; whether Borrower may be liable
    individually or jointly with others; whether Borrower may be obligated as a
    guarantor, surety, or otherwise; whether recovery upon such Indebtedness may
    be or hereafter may become barred by any statute of limitations; and whether
    such Indebtedness may be or hereafter may become otherwise unenforceable.

    LENDER. The word "Lender" means SierraWest Bank, its successors and assigns.

    LOAN. The word "Loan" or "Loans" means and includes without limitation any
    and all commercial loans and financial accommodations from Lender to
    Borrower, whether now or hereafter existing, and however evidenced,
    including without limitation those loans and financial accommodations
    described herein or described on any exhibit or schedule attached to this
    Agreement from time to time.

    NOTE. The word "Note" means and includes without limitation Borrower's
    promissory note or notes, if any, evidencing Borrower's Loan obligations in
    favor of Lender, as well as any substitute, replacement or refinancing note
    or notes therefor.

    PERMITTED LIENS. The words "Permitted Liens" mean: (a) liens and security
    interests securing Indebtedness owed by Borrower to Lender; (b) liens for
    taxes, assessments, or similar charges either not yet due or being contested
    in good faith; (c) liens of materialmen, mechanics, warehousemen, or
    carriers, or other like liens arising in the ordinary course of business and
    securing obligations which are not yet delinquent; (d) purchase money liens
    or purchase money security interests upon or in any property acquired or
    held by Borrower in the ordinary course of business to secure indebtedness
    outstanding on the date of this Agreement or permitted to be incurred under
    the paragraph of this Agreement titled "Indebtedness and Liens"; (e) liens
    and security interests which, as of the date of this Agreement, have been
    disclosed to and approved by the Lender in writing; and (f) those liens and
    security interests which in the aggregate constitute an immaterial and
    insignificant monetary amount with respect to the net value of Borrower's
    assets.

    RELATED DOCUMENTS. The words "Related Documents" mean and include without
    limitation all promissory notes, credit agreements, loan agreements,
    environmental agreements, guaranties, security agreements, mortgages, deeds
    of trust, and all other instruments, agreements and documents, whether now
    or hereafter existing, executed in connection with the Indebtedness.

<PAGE>   50
09-01-1999                   BUSINESS LOAN AGREEMENT
LOAN NO 3400269949                 (CONTINUED)                            PAGE 2
================================================================================

    SECURITY AGREEMENT. The words "Security Agreement" mean and include without
    limitation any agreements, promises, covenants, arrangements, understandings
    or other agreements, whether created by law, contract, or otherwise,
    evidencing, governing, representing, or creating a Security Interest.

    SECURITY INTEREST. The words "Security Interest" mean and include without
    limitation any type of collateral security, whether in the form of a lien,
    charge, mortgage, deed of trust, assignment, pledge, chattel mortgage,
    chattel trust, factor's lien equipment trust conditional sale trust receipt,
    lien or title retention contract, lease or consignment intended as a
    security device, or any other security or lien interest whatsoever, whether
    created by law, contract, or otherwise.

CONDITIONS PRECEDENT TO EACH ADVANCE. Lender's obligation to make the initial
Loan Advance and each subsequent Loan Advance under this Agreement shall be
subject to the fulfillment to Lender's satisfaction of all of the conditions set
forth in this Agreement and in the Related Documents.

    LOAN DOCUMENTS. Borrower shall provide to Lender in form satisfactory to
    Lender the following documents for the Loan: (a) the Note, (b) Security
    Agreements granting to Lender security interests in the Collateral, (c)
    Financing Statements perfecting Lender's Security Interests; (d) evidence of
    insurance as required below; and (e) any other documents required under this
    Agreement or by Lender or its counsel.

    BORROWER'S AUTHORIZATION. Borrower shall have provided in form and substance
    satisfactory to Lender properly certified resolutions, duly authorizing the
    execution and delivery of this Agreement, the Note and the Related
    Documents, and such other authorizations and other documents and instruments
    as Lender or its counsel, in their sole discretion, may require.

    PAYMENT OF FEES AND EXPENSES. Borrower shall have paid to Lender all fees,
    charges, and other expenses which are then due and payable as specified in
    this Agreement or any Related Document.

    REPRESENTATIONS AND WARRANTIES. The representations and warranties set forth
    in this Agreement, in the Related Documents, and in any document or
    certificate delivered to Lender under this Agreement are true and correct.

    NO EVENT OF DEFAULT. There shall not exist at the time of any advance a
    condition which would constitute an Event of Default under this Agreement.

REPRESENTATIONS AND WARRANTIES. Borrower represents and warrants to Lender, as
of the date of this Agreement, as of the date of each disbursement of Loan
proceeds, as of the date of any renewal, extension or modification of any Loan,
and at all times any Indebtedness exists:

    ORGANIZATION. Borrower is a corporation which is duly organized, validly
    existing, and in good standing under the laws of the State of California and
    is validly existing and in good standing in all states in which Borrower is
    doing business. Borrower has the full power and authority to own its
    properties and to transact the businesses in which it is presently engaged
    or presently proposes to engage. Borrower also is duly qualified as a
    foreign corporation and is in good standing in all states in which the
    failure to so qualify would have a material adverse effect on its business
    of financial condition.

    AUTHORIZATION. The execution, delivery, and performance of this Agreement
    and all Related Documents by Borrower, to the extent to be executed,
    delivered or performed by Borrower, have been duly authorized by all
    necessary action by Borrower; do not require the consent or approval of any
    other person, regulatory authority or governmental body; and do not conflict
    with, result in a violation of, or constitute a default under (a) any
    provision of its articles of incorporation or organization, or bylaws, or
    any agreement or other instrument binding upon Borrower or (b) any law,
    governmental regulation, court decree, or order applicable to Borrower.

    FINANCIAL INFORMATION. Each financial statement of Borrower supplied to
    Lender truly and completely disclosed Borrower's financial condition as of
    the date of the statement, and there has been no material adverse change in
    Borrower's financial condition subsequent to the date of the most recent
    financial statement supplied to Lender. Borrower has no material contingent
    obligations except as disclosed in such financial statements.

    LEGAL EFFECT. This Agreement constitutes, and any instrument or agreement
    required hereunder to be given by Borrower when delivered will constitute,
    legal, valid and binding obligations of Borrower enforceable against
    Borrower in accordance with their respective terms.

    PROPERTIES. Except as contemplated by this Agreement or as previously
    disclosed in Borrower's financial statements or in writing to Lender and as
    accepted by Lender, and except for property tax liens for taxes not
    presently due and payable, Borrower owns and has good title to all of
    Borrower's properties free and clear of all Security Interests, and has not
    executed any security documents or financing statements relating to such
    properties. All of Borrower's properties are titled in Borrower's legal
    name, and Borrower has not used, or filed a financing statement under, any
    other name for at least the last five (5) years.

    LITIGATION AND CLAIMS. No litigation, claim, investigation, administrative
    proceeding or similar action (including those for unpaid taxes) against
    Borrower is pending or threatened, and no other event has occurred which may
    materially adversely affect Borrower's financial condition or properties,
    other than litigation, claims, or other events, if any, that have been
    disclosed to and acknowledged by Lender in writing.

    TAXES. To the best of Borrower's knowledge, all tax returns and reports of
    Borrower that are or were required to be filed, have been filed, and all
    taxes, assessments and other governmental charges have been paid in full,
    except those presently being or to be contested by Borrower in good faith in
    the ordinary course of business and for which adequate reserves have been
    provided.

    LIEN PRIORITY. Unless otherwise previously disclosed to Lender in writing,
    Borrower has not entered into or granted any Security Agreements, or
    permitted the filing or attachment of any Security Interests on or affecting
    any of the Collateral directly or indirectly securing repayment of
    Borrower's Loan and Note, that would be prior or that may in any way be
    superior to Lender's Security Interests and rights in and to such
    Collateral.

    BINDING EFFECT. This Agreement, the Note, all Security Agreements directly
    or indirectly securing repayment of Borrower's Loan and Note and all of the
    Related Documents are binding upon Borrower as well as upon Borrower's
    successors, representatives and assigns, and are legally enforceable in
    accordance with their respective terms.

    COMMERCIAL PURPOSES. Borrower intends to use the Loan proceeds solely for
    business or commercial related purposes.

    EMPLOYEE BENEFIT PLANS. Each employee benefit plan as to which Borrower may
    have any liability complies in all material respects with all applicable
    requirements of law and regulations, and (i) no Reportable Event nor
    Prohibited Transaction (as defined in ERISA) has occurred with respect to
    any such plan, (ii) Borrower has not withdrawn from any such plan or
    initiated steps to do so, (iii) no steps have been taken to terminate any
    such plan, and (iv) there are no unfunded liabilities other than those
    previously disclosed to Lender in writing.

<PAGE>   51
09-01-1999                   BUSINESS LOAN AGREEMENT
LOAN NO 3400269949                 (CONTINUED)                            PAGE 3
================================================================================

    LOCATION OF BORROWER'S OFFICES AND RECORDS. Borrower's place of business, or
    Borrower's Chief executive office, if Borrower has more than one place of
    business, is located at 3333 VACA VALLEY PARKWAY, SUITE 1000, VACAVILLE, CA
    95688-9412. Unless Borrower has designated otherwise in writing this
    location is also the office or offices where Borrower keeps its records
    concerning the Collateral.

    INFORMATION. All information heretofore or contemporaneously herewith
    furnished by Borrower to Lender for the purposes of or in connection with
    this Agreement or any transaction contemplated hereby is, and all
    information hereafter furnished by or on behalf of Borrower to Lender will
    be, true and accurate in every material respect on the date as of which such
    information is dated or certified; and none of such information is or will
    be incomplete by omitting to state any material fact necessary to make such
    information not misleading.

    SURVIVAL OF REPRESENTATIONS AND WARRANTIES. Borrower understands and agrees
    that Lender, without independent investigation, is relying upon the above
    representations and warranties in making the above referenced Loan to
    Borrower. Borrower further agrees that the foregoing representations and
    warranties shall be continuing in nature and shall remain in full force and
    effect until such time as Borrower's Indebtedness shall be paid in full, or
    until this Agreement shall be terminated in the manner provided above,
    whichever is the last to occur.

AFFIRMATIVE COVENANTS. Borrower covenants and agrees with Lender that, while
this Agreement is in effect, Borrower will:

    LITIGATION. Promptly inform Lender in writing of (a) all material adverse
    changes in Borrower's financial condition, and (b) all existing and all
    threatened litigation, claims, investigations, administrative proceedings or
    similar actions affecting Borrower or any Guarantor which could materially
    affect the financial condition of Borrower or the financial condition of any
    Guarantor.

    FINANCIAL RECORDS. Maintain its books and records in accordance with
    generally accepted accounting principles, applied on a consistent basis, and
    permit Lender to examine and audit Borrower's books and records at all
    reasonable times.

    ADDITIONAL INFORMATION. Furnish such additional information and statements,
    lists of assets and liabilities, agings of receivables and payables,
    inventory schedules, budgets, forecasts, tax returns, and other reports with
    respect to Borrower's financial condition and business operations as Lender
    may request from time to time.

    INSURANCE. Maintain fire and other risk insurance, public liability
    insurance, and such other insurance as Lender may require with respect to
    Borrower's properties and operations, in form, amounts, coverages and with
    insurance companies reasonably acceptable to Lender. Borrower, upon request
    of Lender, will deliver to Lender from time to time the policies or
    certificates of insurance in form satisfactory to Lender, including
    stipulations that coverages will not be cancelled or diminished without at
    least ten (10) days' prior written notice to Lender. Each insurance policy
    also shall include an endorsement providing that coverage in favor of Lender
    will not be impaired in any way by any act, omission or default of Borrower
    or any other person. In connection with all policies covering assets in
    which Lender holds or is offered a security interest for the Loans, Borrower
    will provide Lender with such loss payable or other endorsements as Lender
    may require.

    INSURANCE REPORTS. Furnish to Lender, upon request of Lender, reports on
    each existing insurance policy showing such information as Lender may
    reasonably request, including without limitation the following: (a) the name
    of the insurer; (b) the risks insured; (c) the amount of the policy; (d) the
    properties insured; (e) the then current property values on the basis of
    which insurance has been obtained, and the manner of determining those
    values; and (f) the expiration date of the policy. In addition, upon request
    of Lender (however not more often than annually), Borrower will have an
    independent appraiser satisfactory to Lender determine, as applicable, the
    actual cash value or replacement cost of any Collateral. The cost of such
    appraisal shall be paid by Borrower.

    OTHER AGREEMENTS. Comply with all terms and conditions of all other
    agreements, whether now or hereafter existing, between Borrower and any
    other party and notify Lender immediately in writing of any default in
    connection with any other such agreements.

    LOAN PROCEEDS. Use all Loan proceeds solely for Borrower's business
    operations, unless specifically consented to the contrary by Lender in
    writing.

    TAXES, CHARGES AND LIENS. Pay and discharge when due all of its indebtedness
    and obligations, including without limitation all assessments, taxes,
    governmental charges, levies and liens, of every kind and nature, imposed
    upon Borrower or its properties, income, or profits, prior to the date on
    which penalties would attach, and all lawful claims that, if unpaid, might
    become a lien or charge upon any of Borrower's properties, income, or
    profits. Provided however, Borrower will not be required to pay and
    discharge any such assessment, tax, charge, levy, lien or claim so long as
    (a) the legality of the same shall be contested in good faith by appropriate
    proceedings, and (b) Borrower shall have established on its books adequate
    reserves with respect to such contested assessment, tax, charge, levy, lien,
    or claim in accordance with generally accepted accounting practices.
    Borrower, upon demand of Lender, will furnish to Lender evidence of payment
    of the assessments, taxes, charges, levies, liens and claims and will
    authorize the appropriate governmental official to deliver to Lender at any
    time a written statement of any assessments, taxes, charges, levies, liens
    and claims against Borrower's properties, income, or profits.

    PERFORMANCE. Perform and comply with all terms, conditions, and provisions
    set forth in this Agreement and in the Related Documents in a timely manner,
    and promptly notify Lender if Borrower learns of the occurrence of any event
    which constitutes an Event of Default under this Agreement or under any of
    the Related Documents.

    OPERATIONS. Maintain executive and management personnel with substantially
    the same qualifications and experience as the present executive and
    management personnel; provide written notice to Lender of any change in
    executive and management personnel; conduct its business affairs in a
    reasonable and prudent manner and in compliance with all applicable federal,
    state and municipal laws, ordinances, rules and regulations respecting its
    properties, charters, businesses and operations, including without
    limitation, compliance with the Americans With Disabilities Act and with all
    minimum funding standards and other requirements of ERISA and other laws
    applicable to Borrower's employee benefit plans.

    INSPECTION. Permit employees or agents of Lender at any reasonable time to
    inspect any and all Collateral for the Loan or Loans and Borrower's other
    properties and to examine or audit Borrower's books, accounts, and records
    and to make copies and memoranda of Borrower's books accounts, and records.
    If Borrower now or at any time hereafter maintains any records (including
    without limitation computer generated records and computer software programs
    for the generation of such records) in the possession of a third party,
    Borrower, upon request of Lender, shall notify such party to permit Lender
    free access to such records at all reasonable times and to provide Lender
    with copies of any records it may request, all at Borrower's expense.

    COMPLIANCE CERTIFICATE. Unless waived in writing by Lender, provide Lender
    at least annually and at the time of each disbursement of Loan proceeds with
    a certificate executed by Borrower's chief financial officer, or other
    officer or person acceptable to Lender, certifying that the representations
    and warranties set forth in this Agreement are true and correct as of the
    date of the certificate and further certifying that, as of the date of the
    certificate, no Event of Default exists under this Agreement.

<PAGE>   52
09-01-1999                   BUSINESS LOAN AGREEMENT
LOAN NO 3400269949                 (CONTINUED)                            PAGE 4
================================================================================

    ENVIRONMENTAL COMPLIANCE AND REPORTS. Borrower shall comply in all respects
    with all covenants, terms, conditions and provisions set forth in the
    Environmental Indemnity Certificate and Agreement executed in connection
    with the Loan.

    ADDITIONAL ASSURANCES. Make, execute and deliver to Lender such promissory
    notes, mortgages, deeds of trust, security agreements, financing statements,
    instruments, documents and other agreements as Lender or its attorneys may
    reasonably request to evidence and secure the Loans and to perfect all
    Security Interests.

NEGATIVE COVENANTS. Borrower covenants and agrees with Lender that while this
Agreement is in effect, Borrower shall not, without the prior written consent of
Lender:

    INDEBTEDNESS AND LIENS. (a) Except for trade debt incurred in the normal
    course of business and indebtedness to Lender contemplated by this
    Agreement, create, incur or assume indebtedness for borrowed money,
    including capital leases, (b) except as allowed as a Permitted Lien, sell,
    transfer, mortgage, assign, pledge, lease, grant a security interest in, or
    encumber any of Borrower's assets, or (c) sell with recourse any of
    Borrower's accounts, except to Lender.

    CONTINUITY OF OPERATIONS. (a) Engage in any business activities
    substantially different than those in which Borrower is presently engaged,
    (b) cease operations, liquidate, merge, transfer, acquire or consolidate
    with any other entity, change ownership, change its name, dissolve or
    transfer or sell Collateral out of the ordinary course of business, (c) pay
    any dividends on Borrower's stock (other than dividends payable in its
    stock), provided, however that notwithstanding the foregoing, but only so
    long as no Event of Default has occurred and is continuing or would result
    from the payment of dividends, if Borrower is a "Subchapter S Corporation"
    (as defined in the Internal Revenue Code of 1986, as amended), Borrower may
    pay cash dividends on its stock to its shareholders from time to time in
    amounts necessary to enable the shareholders to pay income taxes and make
    estimated income tax payments to satisfy their liabilities under federal and
    state law which arise solely from their status as Shareholders of a
    Subchapter S Corporation because of their ownership of shares of stock of
    Borrower, or (d) purchase or retire any of Borrower's outstanding shares or
    alter or amend Borrower's capital structure.

    LOANS, ACQUISITIONS AND GUARANTIES. (a) Loan, invest in or advance money or
    assets, (b) purchase, create or acquire any interest in any other enterprise
    or entity, or (c) incur any obligation as surety or guarantor other than in
    the ordinary course of business.

CESSATION OF ADVANCES. If Lender has made any commitment to make any Loan to
Borrower, whether under this Agreement or under any other agreement, Lender
shall have no obligation to make Loan Advances or to disburse Loan proceeds if:
(a) Borrower or any Guarantor is in default under the terms of this Agreement or
any of the Related Documents or any other agreement that Borrower or any
Guarantor has with Lender; (b) Borrower or any Guarantor becomes insolvent,
files a petition in bankruptcy or similar proceedings, or is adjudged a
bankrupt; (c) there occurs a material adverse change in Borrower's financial
condition, in the financial condition of any Guarantor, or in the value of any
Collateral securing any Loan; (d) any Guarantor seeks, claims or otherwise
attempts to limit, modify or revoke such Guarantor's guaranty of the Loan or any
other loan with Lender; or (e) Lender in good faith deems itself insecure, even
though no Event of Default shall have occurred.

FINANCIAL COVENANTS.

1. ANNUALLY AUDITED FINANCIAL STATEMENTS WITHIN 90 DAYS OF FISCAL YEAR END.

2. QUARTERLY INTERNAL FINANCIAL STATEMENTS WITHIN 45 DAYS OF EACH PERIOD.

3. BORROWER TO PROVIDE MONTHLY INVOICES, OPERATING BUDGET AND CAPITAL PURCHASES
BUDGET WITHIN 30 DAYS OF EACH PERIOD.

4. BORROWER TO PROVIDE BANK WITH ANY PERTINENT REVISIONS TO DOW CHEMICAL
COLLABORATION AND LICENSE AGREEMENT.

5. BORROWER TO MAINTAIN CERTIFICATE OF DEPOSIT #2132399 AS PROVIDED FOR IN THE
ASSIGNMENT OF DEPOSIT ACCOUNT AND THE CREDIT APPROVAL REPORT ATTACHED THERETO.

DISBURSEMENT OF FUNDS. DISBURSEMENT OF FUNDS WITH WRITTEN REQUEST BY AUTHORIZED
SIGNERS AND PRESENTATION OF INVOICES SUPPORTING THE DOLLAR AMOUNT OF THE
REQUEST. DISBURSEMENTS WILL BE PAID TO VENDORS DIRECTLY.

PAYMENT TERMS.

BORROWER WILL PAY THIS LOAN IN ACCORDANCE WITH THE FOLLOWING PAYMENT SCHEDULE:
INTEREST ONLY PAYMENTS WILL BE REQUIRED MONTHLY BEGINNING JANUARY 1, 1999. THERE
IS TO BE FOUR ADVANCE PERIODS DURING THE TERM OF THIS NOTE. THE FIRST BEGINNING
ON THIS DATE AND ENDING FEBRUARY 28, 1999. THE SECOND BEGINNING MARCH 1, 1999
AND ENDING MAY 31, 1999. THE THIRD BEGINNING JUNE 1, 1999 AND ENDING AUGUST 31,
1999. THE FOURTH AND FINAL ADVANCE PERIOD BEGINNING SEPTEMBER 1, 1999 AND ENDING
NOVEMBER 30,1999. THE OUTSTANDING BALANCE ON THE LAST DAY OF EACH ADVANCE PERIOD
WILL BE PAID IN FULL BY A NEW NOTE ADVANCE FROM A SEPARATE TERM LOAN TO BE
PROVIDED BY SIERRAWEST BANK THAT WILL AMORTIZE SAID PRINCIPAL BALANCE IN FULL BY
OCTOBER 1, 2001.

HAZARDOUS SUBSTANCES. The terms "hazardous waste," "hazardous substance,"
"disposal", "release," and "threatened release," as used in this Agreement,
shall have the same meanings as set forth in the "CERCLA," "SARA," the Hazardous
Materials Transportation Act, 40 U.S.C. Section 1801, et seq., the Resource
Conservation and Recovery Act, 42 U.S.C. Section 6901, et seq., Chapters 6.5
through 7.7 of Division 20 of the California Health and Safety Code, Section
25100, et seq., or other applicable state or Federal laws, rules, or regulations
adopted pursuant to any of the foregoing. Except as disclosed to and
acknowledged by Lender in writing, Borrower represents and warrants that : (a)
During the period of Borrower's ownership of the properties, there has been no
unauthorized use, generation, manufacture, storage, treatment, disposal, release
or threatened release of any hazardous waste or substance by any person on,
under, about or from any of the properties. (b) Borrower has no knowledge of, or
reason to believe that there has been (i) an unauthorized use, generation,
manufacture, storage, treatment, disposal, release, or threatened release of any
hazardous waste or substance on, under, about or from the properties by any
prior owners or occupants of any of the properties, or (ii) any actual or
threatened litigation or claims of any kind by any person relating to such
matters. (c) Neither Borrower nor any tenant, contractor, agent or other
authorized user of any of the properties shall, in an unauthorized manner, use,
generate, manufacture, store, treat, dispose of, or release any hazardous waste
or substance on, under, about or from any of the properties; and any such
activity shall be conducted in compliance with all applicable federal, state,
and local laws, regulations, and ordinances, including without limitation those
laws, regulations and ordinances described above. As allowed by applicable law
and upon reasonable prior notice lender may enter upon the premises of Borrower
to inspect the properties for compliance with this section of the agreement. Any
inspections or test made by Lender shall be at Borrower's expense and for
Lender's purposes only and shall not be construed to create any responsibility
or liability on the part of Lender to Borrower or to any other person. The
representations and warranties contained herein are based on Borrower's due
diligence in investigating the properties for hazardous waste and hazardous
substances. Borrower hereby (a) releases and waives any

<PAGE>   53
09-01-1999                   BUSINESS LOAN AGREEMENT
LOAN NO 3400269949                 (CONTINUED)                            PAGE 5
================================================================================

future claims against Lender for indemnity or contribution in the event Borrower
becomes liable for cleanup or other costs under any such laws, and (b) agrees to
indemnify and hold harmless Lender against any and all claims, losses,
liabilities, damages, penalties, and expenses which Lender may directly or
indirectly sustain or suffer resulting from a breach of this section of the
Agreement or as a consequence of any unauthorized use, generation, manufacture,
storage, disposal, release or threatened release of a hazardous waste or
substance on the properties. The provisions of this section of the Agreement,
including the obligation to indemnify, shall survive the payment of the
indebtedness and the termination or expiration of this Agreement and shall not
be affected by Lender's acquisition of any interest in any of the properties,
whether by foreclosure or otherwise..

RIGHT OF SETOFF. Borrower grants to Lender a contractual security interest in,
and hereby assigns, conveys, delivers, pledges, and transfers to Lender all
Borrower's right, title and interest in and to, Borrower's accounts with Lender
(whether checking, savings, or some other account), including without limitation
all accounts held jointly with someone else and all accounts Borrower may open
in the future, excluding however all IRA and Keogh accounts, and all trust
accounts for which the grant of a security interest would be prohibited by law.
Borrower authorizes Lender, to the extent permitted by applicable law, to charge
or setoff all sums owing on the Indebtedness against any and all such accounts.

EVENTS OF DEFAULT. Each of the following shall constitute an Event of Default
under this Agreement:

    DEFAULT ON INDEBTEDNESS. Failure of Borrower to make any payment when due on
    the Loans.

    OTHER DEFAULTS. Failure of Borrower or any Grantor to comply with or to
    perform when due any other term, obligation, covenant or condition contained
    in this Agreement or in any of the Related Documents, or failure of Borrower
    to comply with or to perform any other term, obligation, covenant or
    condition contained in any other agreement between Lender and Borrower.

    ENVIRONMENTAL DEFAULT. Failure of any party to comply with or perform when
    due any term, obligation, covenant or condition contained in any
    environmental agreement executed in connection with any Loan.

    DEFAULT IN FAVOR OF THIRD PARTIES. Should Borrower or any Grantor default
    under any loan, extension of credit, security agreement, purchase or sales
    agreement, or any other agreement, in favor of any other creditor or person
    that may materially affect any of Borrower's property or Borrower's or any
    Grantor's ability to repay the Loans or perform their respective obligations
    under this Agreement or any of the Related Documents

    FALSE STATEMENTS. Any warranty, representation or statement made or
    furnished to Lender by or on behalf of Borrower or any Grantor under this
    Agreement or the Related Documents is false or misleading in any material
    respect at the time made or furnished, or becomes false or misleading at any
    time thereafter.

    DEFECTIVE COLLATERALIZATION. This Agreement or any of the Related Documents
    ceases to be in full force and effect (including failure of any Security
    Agreement to create a valid and perfected Security Interest) at any time and
    for any reason.

    INSOLVENCY. The dissolution or termination of Borrower's existence as a
    going business, the insolvency of Borrower, the appointment of a receiver
    for any part of Borrower's property, any assignment for the benefit of
    creditors, any type of creditor workout, or the commencement of any
    proceeding under any bankruptcy or insolvency laws by or against Borrower.

    CREDITOR OR FORFEITURE PROCEEDINGS. Commencement of foreclosure or
    forfeiture proceedings, whether by judicial proceeding, self-help,
    repossession or any other method, by any creditor of Borrower, any creditor
    of any Grantor against any collateral securing the Indebtedness, or by any
    governmental agency. This includes a garnishment, attachment, or levy on or
    of any of Borrower's deposit accounts with Lender. However, this Event of
    Default shall not apply if there is a good faith dispute by Borrower or
    Grantor, as the case may be, as to the validity or reasonableness of the
    claim which is the basis of the creditor or forfeiture proceeding, and if
    Borrower or Grantor gives Lender written notice of the creditor or
    forfeiture proceeding and furnishes reserves or a surety bond for the
    creditor or forfeiture proceeding satisfactory to Lender.

    EVENTS AFFECTING GUARANTOR. Any of the preceding events occurs with respect
    to any Guarantor of any of the Indebtedness or any Guarantor dies or becomes
    incompetent, or revokes or disputes the validity of, or liability under, any
    Guaranty of the Indebtedness. Lender, at its option, may, but shall not be
    required to, permit the Guarantor's estate to assume unconditionally the
    obligations arising under the guaranty in a manner satisfactory to Lender,
    and, in doing so, cure the Event of Default.

    CHANGE IN OWNERSHIP. Any change in ownership of twenty-five percent (25%) or
    more of the common stock of Borrower.

    ADVERSE CHANGE. A material adverse change occurs in Borrower's financial
    condition, or Lender believes the prospect of payment or performance of the
    Indebtedness is impaired.

    INSECURITY. Lender, in good faith, deems itself insecure.

    RIGHT TO CURE. If any default, other than a Default on Indebtedness, is
    curable and if Borrower or Grantor, as the case may be, has not been given a
    notice of a similar default within the preceding twelve (12) months, it may
    be cured (and no Event of Default will have occurred) if Borrower or
    Grantor, as the case may be, after receiving written notice from Lender
    demanding cure of such default: (a) cures the default within fifteen (15)
    days; or (b) if the cure requires more than fifteen (15) days, immediately
    initiates steps which Lender deems in Lender's sole discretion to be
    sufficient to cure the default and thereafter continues and completes all
    reasonable and necessary steps sufficient to produce compliance as soon as
    reasonably practical.

EFFECT OF AN EVENT OF DEFAULT. If any Event of Default shall occur, except where
otherwise provided in this Agreement or the Related Documents, all commitments
and obligations of Lender under this Agreement or the Related Documents or any
other agreement immediately will terminate and, at Lender's option, all
Indebtedness immediately will become due and payable, all without notice of any
kind to Borrower, except that in the case of an Event of Default of the type
described in the "Insolvency" subsection above, such acceleration shall be
automatic and not optional. In addition, Lender shall have all the rights and
remedies provided in the Related Documents or available at law, in equity, or
otherwise. Except as may be prohibited by applicable law, all of Lender's rights
and remedies shall be cumulative and may be exercised singularly or
concurrently. Election by Lender to pursue any remedy shall not exclude pursuit
of any other remedy, and an election to make expenditures or to take action to
perform an obligation of Borrower or of any Grantor shall not affect Lender's
right to declare a default and to exercise its rights and remedies.

MISCELLANEOUS PROVISIONS. The following miscellaneous provisions are a part of
this Agreement:

    AMENDMENTS. This Agreement, together with any Related Documents, constitutes
    the entire understanding and agreement of the parties as to the matters set
    forth in this Agreement. No alteration of or amendment to this Agreement
    shall be effective unless given in writing and signed by the party or
    parties sought to be charged or bound by the alteration or amendment.

<PAGE>   54
09-01-1999                   BUSINESS LOAN AGREEMENT
LOAN NO 3400269949                 (CONTINUED)                            PAGE 6
================================================================================

    APPLICABLE LAW. THIS AGREEMENT HAS BEEN DELIVERED TO LENDER AND ACCEPTED BY
    LENDER IN THE STATE OF CALIFORNIA. IF THERE IS A LAWSUIT, BORROWER AGREES
    UPON LENDER'S REQUEST TO SUBMIT TO THE JURISDICTION OF THE COURTS OF NEVADA
    COUNTY, THE STATE OF CALIFORNIA. THIS AGREEMENT SHALL BE GOVERNED BY AND
    CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF CALIFORNIA.

    CAPTION HEADINGS. Caption headings in this Agreement are for convenience
    purposes only and are not to be used to interpret or define the provisions
    of this Agreement.

    MULTIPLE PARTIES; CORPORATE AUTHORITY. All obligations of Borrower under
    this Agreement shall be joint and several, and all references to Borrower
    shall mean each and every Borrower. This means that each of the persons
    signing below is responsible for all obligations in this Agreement.

    CONSENT TO LOAN PARTICIPATION. Borrower agrees and consents to Lender's sale
    or transfer, whether now or later, of one or more participation interests in
    the Loans to one or more purchasers, whether related or unrelated to Lender.
    Lender may provide, without any limitation whatsoever, to any one or more
    purchasers, or potential purchasers, any information or knowledge Lender may
    have about Borrower or about any other matter relating to the Loan, and
    Borrower hereby waives any rights to privacy it may have with respect to
    such matters. Borrower additionally waives any and all notices of sale of
    participation interests, as well as all notices of any repurchase of such
    participation interests. Borrower also agrees that the purchasers of any
    such participation interests will be considered as the absolute owners of
    such interests in the Loans and will have all the rights granted under the
    participation agreement or agreements governing the sale of such
    participation interests. Borrower further waives all rights of offset or
    counterclaim that it may have now or later against Lender or against any
    purchaser of such a participation interest and unconditionally agrees that
    either Lender or such purchaser may enforce Borrower's obligation under the
    Loans irrespective of the failure or insolvency of any holder of any
    interest in the Loans. Borrower further agrees that the purchaser of any
    such participation interests may enforce its interests irrespective of any
    personal claims or defenses that Borrower may have against Lender.

    COSTS AND EXPENSES. Borrower agrees to pay upon demand all of Lender's
    expenses, including without limitation attorneys' fees, incurred in
    connection with the preparation, execution, enforcement, modification and
    collection of this Agreement or in connection with the Loans made pursuant
    to this Agreement. Lender may pay someone else to help collect the Loans and
    to enforce this Agreement, and Borrower will pay that amount. This includes,
    subject to any limits under applicable law, Lender's attorneys' fees and
    Lender's legal expenses, whether or not there is a lawsuit, including
    attorneys' fees for bankruptcy proceedings (including efforts to modify or
    vacate any automatic stay or injunction), appeals, and any anticipated
    post-judgment collection services. Borrower also will pay any court costs,
    in addition to all other sums provided by law.

    NOTICES. All notices required to be given under this Agreement shall be
    given in writing, may be sent by telefacsimile (unless otherwise required by
    law), and shall be effective when actually delivered or when deposited with
    a nationally recognized overnight courier or deposited in the United States
    mail, first class, postage prepaid, addressed to the party to whom the
    notice is to be given at the address shown above. Any party may change its
    address for notices under this Agreement by giving formal written notice to
    the other parties, specifying that the purpose of the notice is to change
    the party's address. To the extent permitted by applicable law, if there is
    more than one Borrower, notice to any Borrower will constitute notice to all
    Borrowers. For notice purposes, Borrower will keep Lender informed at all
    times of Borrower's current address(es).

    SEVERABILITY. If a court of competent jurisdiction finds any provision of
    this Agreement to be invalid or unenforceable as to any person or
    circumstance, such finding shall not render that provision invalid or
    unenforceable as to any other persons or circumstances. If feasible, any
    such offending provision shall be deemed to be modified to be within the
    limits of enforceability or validity; however, if the offending provision
    cannot be so modified, it shall be stricken and all other provisions of this
    Agreement in all other respects shall remain valid and enforceable.

    SUBSIDIARIES AND AFFILIATES OF BORROWER. To the extent the context of any
    provisions of this Agreement makes it appropriate, including without
    limitation any representation, warranty or covenant, the word "Borrower" as
    used herein shall include all subsidiaries and affiliates of Borrower.
    Notwithstanding the foregoing however, under no circumstances shall this
    Agreement be construed to require Lender to make any Loan or other financial
    accommodation to any subsidiary or affiliate of Borrower.

    SUCCESSORS AND ASSIGNS. All covenants and agreements contained by or on
    behalf of Borrower shall bind its successors and assigns and shall inure to
    the benefit of Lender, its successors and assigns. Borrower shall not,
    however, have the right to assign its rights under this Agreement or any
    interest therein, without the prior written consent of Lender.

    SURVIVAL. All warranties, representations, and covenants made by Borrower in
    this Agreement or in any certificate or other instrument delivered by
    Borrower to Lender under this Agreement shall be considered to have been
    relied upon by Lender and will survive the making of the Loan and delivery
    to Lender of the Related Documents, regardless of any investigation made by
    Lender or on Lender's behalf.

    TIME IS OF THE ESSENCE. Time is of the essence in the performance of this
    Agreement.

    WAIVER. Lender shall not be deemed to have waived any rights under this
    Agreement unless such waiver is given in writing and signed by Lender, No
    delay or omission on the part of Lender in exercising any right shall
    operate as a waiver of such right or any other fight. A waiver by Lender of
    a provision of this Agreement shall not prejudice or constitute a waiver of
    Lender's right otherwise to demand strict compliance with that provision or
    any other provision of this Agreement. No prior waiver by Lender, nor any
    course of dealing between Lender and Borrower, or between Lender and any
    Grantor, shall constitute a waiver of any of Lender's rights or of any
    obligations of Borrower or of any Grantor as to any future transactions.
    Whenever the consent of Lender is required under this Agreement the granting
    of such consent by Lender in any instance shall not constitute continuing
    consent in subsequent instances where such consent is required, and in all
    cases such consent may be granted or withheld in the sole discretion of
    Lender.

<PAGE>   55
09-01-1999                   BUSINESS LOAN AGREEMENT
LOAN NO 3400269949                 (CONTINUED)                            PAGE 7
================================================================================

BORROWER ACKNOWLEDGES HAVING READ ALL THE PROVISIONS OF THIS BUSINESS LOAN
AGREEMENT, AND BORROWER AGREES TO ITS TERMS. THIS AGREEMENT IS DATED AS OF JUNE
7,1999.

BORROWER:

BIOSOURCE TECHNOLOGIES, INC.

By:  Robert L. Erwin                         By: Michael D. Centron
     --------------------------------------      -----------------------------
     ROBERT L. ERWIN, CHAIRMAN OF THE BOARD      MICHAEL D. CENTRON, TREASURER.

LENDER:

SierraWest Bank

By:
    -------------------------------
    Authorized Officer

<PAGE>   56
                                 PROMISSORY NOTE

<TABLE>
<CAPTION>
    PRINCIPAL         LOAN DATE       MATURITY       LOAN NO    CALL   COLLATERAL  ACCOUNT    OFFICER  INITIALS
<S>                  <C>             <C>           <C>          <C>    <C>         <C>        <C>      <C>
  $1,503,985.26      06-07-1999      10-01-2001    3400269949    11                 111721      791
</TABLE>

  References in the shaded area are for Lender's use only and do not limit the
         applicability of this document to any particular loan or item.

<TABLE>
<S>                                              <C>
BORROWER: BIOSOURCE TECHNOLOGIES, INC.  (TI N:   LENDER: SIERRAWEST BANK
          77-0154648)                                    CENTRAL PACIFIC REGION
          3333 VACA VALLEY PARKWAY, SUITE 1000           1100 TEXAS ST
          VACAVILLE, CA 95688-9412                       FAIRFIELD, CA 94533
</TABLE>

PRINCIPAL AMOUNT:            INITIAL RATE:        DATE OF NOTE:
$1,503,985.26                7.750%               JUNE 7, 1999

PROMISE TO PAY. BIOSOURCE TECHNOLOGIES, INC. ("Borrower") promises to pay to
SierraWest Bank ("Lender"), or order, in lawful money of the United States of
America, the principal amount of One Million Five Hundred Three Thousand Nine
Hundred Eighty Five & 26/100 Dollars ($1,503,985.26), together with Interest on
the unpaid principal balance from June 7, 1999, until paid in full.

PAYMENT. SUBJECT TO ANY PAYMENT CHANGES RESULTING FROM CHANGES IN THE INDEX,
BORROWER WILL PAY THIS LOAN IN 27 PAYMENTS OF $58,900.03 EACH PAYMENT AND AN
IRREGULAR LAST PAYMENT ESTIMATED AT $58,900.16. BORROWER'S FIRST PAYMENT IS DUE
JULY 1, 1999, AND ALL SUBSEQUENT PAYMENTS ARE DUE ON THE SAME DAY OF EACH MONTH
AFTER THAT. BORROWER'S FINAL PAYMENT WILL BE DUE ON OCTOBER 1, 2001, AND WILL BE
FOR ALL PRINCIPAL AND ALL ACCRUED INTEREST NOT YET PAID. PAYMENTS INCLUDE
PRINCIPAL AND INTEREST. The annual interest rate for this Note is computed on a
365/360 basis; that is, by applying the ratio of the annual interest rate over a
year of 360 days, multiplied by the outstanding principal balance, multiplied by
the actual number of days the principal balance is outstanding. Borrower will
pay Lender at Lender's address shown above or at such other place as Lender may
designate in writing. Unless otherwise agreed or required by applicable law,
payments will be applied first to accrued unpaid interest, then to principal,
and any remaining amount to any unpaid collection costs and late charges.

VARIABLE INTEREST RATE. The interest rate on this Note is subject to change from
time to time based on changes in an independent index which is the Prime rate as
published in the western edition of the Wall Street Journal (the "Index"). The
Index is not necessarily the lowest rate charged by Lender on its loans. If the
Index becomes unavailable during the term of this loan, Lender may designate a
substitute index after notice to Borrower. Lender will tell Borrower the current
Index rate upon Borrower's request. Borrower understands that Lender may make
loans based on other rates as well. The interest rate change will not occur more
often than each DAY. THE INDEX CURRENTLY IS 7.750%. THE INTEREST RATE TO BE
APPLIED TO THE UNPAID PRINCIPAL BALANCE OF THIS NOTE WILL BE AT A RATE EQUAL TO
THE INDEX, RESULTING IN AN INITIAL RATE OF 7.750%. NOTICE: Under no
circumstances will the interest rate on this Note be more than the maximum rate
allowed by applicable law. Whenever increases occur in the interest rate,
Lender, at its option, may do one or more of the following: (a) increase
Borrower's payments to ensure Borrower's loan will pay off by its original final
maturity date, (b) increase Borrower's payments to cover accruing interest, (c)
increase the number of Borrower's payments, and (d) continue Borrower's payments
at the same amount and increase Borrower's final payment.

PREPAYMENT. Borrower may pay without penalty all or a portion of the amount owed
earlier than it is due. Early payments will not, unless agreed to by Lender in
writing, relieve Borrower of Borrower's obligation to continue to make payments
under the payment schedule. Rather, they will reduce the principal balance due
and may result in Borrower making fewer payments.

LATE CHARGE. If a payment is 10 days or more late, Borrower will be charged
5.000% of the regularly scheduled payment or $15.00, whichever is greater.

DEFAULT. Borrower will be in default if any of the following happens: (a)
Borrower fails to make any payment when due. (b) Borrower breaks any promise
Borrower has made to Lender, or Borrower fails to comply with or to perform when
due any other term, obligation, covenant, or condition contained in this Note or
any agreement related to this Note, or in any other agreement or loan Borrower
has with Lender. (c) Borrower defaults under any loan, extension of credit,
security agreement, purchase or sales agreement, or any other agreement, in
favor of any other creditor or person that may materially affect any of
Borrower's property or Borrower's ability to repay this Note or perform
Borrower's obligations under this Note or any of the Related Documents. (d) Any
representation or statement made or furnished to Lender by Borrower or on
Borrower's behalf is false or misleading in any material respect either now or
at the time made or furnished. (e) Borrower becomes insolvent, a receiver is
appointed for any part of Borrower's property, Borrower makes an assignment for
the benefit of creditors, or any proceeding is commenced either by Borrower or
against Borrower under any bankruptcy or insolvency laws. (f) Any creditor tries
to take any of Borrower's property on or in which Lender has a lien or security
interest. This includes a garnishment of any of Borrower's accounts with Lender.
(g) Any guarantor dies or any of the other events described in this default
section occurs with respect to any guarantor of this Note. (h) A material
adverse change occurs in Borrower's financial condition, or Lender believes the
prospect of payment or performance of the Indebtedness is impaired. (1) Lender
in good faith deems itself insecure.

If any default, other than a default in payment, is curable and if Borrower has
not been given a notice of a breach of the same provision of this Note within
the preceding twelve (12) months, it may be cured (and no event of default will
have occurred) if Borrower, after receiving written notice from Lender demanding
cure of such default: (a) cures the default within fifteen (15) days; or (b) if
the cure requires more than fifteen (15) days, immediately initiates steps which
Lender deems in Lender's sole discretion to be sufficient to cure the default
and thereafter continues and completes all reasonable and necessary steps
sufficient to produce compliance as soon as reasonably practical.

LENDER'S RIGHTS. Upon default, Lender may declare the entire unpaid principal
balance on this Note and all accrued unpaid interest immediately due, without
notice, and then Borrower will pay that amount. Upon Borrower's failure to pay
all amounts declared due pursuant to this section, including failure to pay upon
final maturity, Lender, at its option, may also, if permitted under applicable
law, increase the variable interest rate on this Note to 5.000 percentage points
over the Index. Lender may hire or pay someone else to help collect this Note if
Borrower does not pay. Borrower also will pay Lender that amount. This includes,
subject to any limits under applicable law, Lender's attorneys' fees and
Lender's legal expenses whether or not there is a lawsuit, including attorneys'
fees and legal expenses for bankruptcy proceedings (including efforts to modify
or vacate any automatic stay or injunction), appeals, and any anticipated
post-judgment collection services. Borrower also will pay any court costs, in
addition to all other sums provided by law. THIS NOTE HAS BEEN DELIVERED TO
LENDER AND ACCEPTED BY LENDER IN THE STATE OF CALIFORNIA. IF THERE IS A LAWSUIT,
BORROWER AGREES UPON LENDER'S REQUEST TO SUBMIT TO THE JURISDICTION OF THE
COURTS OF NEVADA COUNTY, THE STATE OF CALIFORNIA. THIS NOTE SHALL BE GOVERNED BY
AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF CALIFORNIA.

<PAGE>   57
09-01-1999                       PROMISSORY NOTE
LOAN NO 3400269949                  (CONTINUED)                           PAGE 2
================================================================================

RIGHT OF SETOFF. Borrower grants to Lender a contractual security interest in,
and hereby assigns, conveys, delivers, pledges, and transfers to Lender all
Borrower's right, title and interest in and to, Borrower's accounts with Lender
(whether checking, savings, or some other account), including without limitation
all accounts held jointly with someone else and all accounts Borrower may open
in the future, excluding however all IRA and Keogh accounts, and all trust
accounts for which the grant of a security interest would be prohibited by law.
Borrower authorizes Lender, to the extent permitted by applicable law, to charge
or setoff all sums owing on this Note against any and all such accounts.

DISBURSEMENT OF FUNDS. DISBURSEMENT OF FUNDS WITH WRITTEN REQUEST BY AUTHORIZED
SIGNERS AND PRESENTATION OF INVOICES SUPPORTING THE DOLLAR AMOUNT OF THE
REQUEST. DISBURSEMENTS WILL BE PAID TO VENDORS DIRECTLY.

CROSS-COLLATERALIZATION. THIS NOTE IS CROSS-COLLATERALIZED WITH NOTE 3400069949
DATED NOVEMBER 30, 1998 AND NOTE 3400169949 BETWEEN BIOSOURCE TECHNOLOGIES, INC.
AND SIERRAWEST BANK.

GENERAL PROVISIONS. Lender may delay or forgo enforcing any of its rights or
remedies under this Note without losing them. Borrower and any other person who
signs, guarantees or endorses this Note, to the extent allowed by law, waive any
applicable statute of limitations, presentment, demand for payment, protest and
notice of dishonor. Upon any change in the terms of this Note, and unless
otherwise expressly stated in writing, no party who signs this Note, whether as
maker, guarantor, accommodation maker or endorser, shall be released from
liability. All such parties agree that Lender may renew or extend (repeatedly
and for any length of time) this loan, or release any party or guarantor or
collateral; or impair, fail to realize upon or perfect Lender's security
interest in the collateral; and take any other action deemed necessary by Lender
without the consent of or notice to anyone. All such parties also agree that
Lender may modify this loan without the consent of or notice to anyone other
than the party with whom the modification is made.

PRIOR TO SIGNING THIS NOTE, BORROWER READ AND UNDERSTOOD ALL THE PROVISIONS OF
THIS NOTE, INCLUDING THE VARIABLE INTEREST RATE PROVISIONS. BORROWER AGREES TO
THE TERMS OF THE NOTE AND ACKNOWLEDGES RECEIPT OF A COMPLETED COPY OF THE NOTE.

BORROWER:

BIOSOURCE TECHNOLOGIES, INC.

By:                                         By:
    --------------------------------------      ------------------------------
    ROBERT L. ERWIN, CHAIRMAN OF THE BOARD      MICHAEL D. CENTRON, TREASURER.

<PAGE>   58
                     DISBURSEMENT REQUEST AND AUTHORIZATION

<TABLE>
<CAPTION>
    PRINCIPAL         LOAN DATE       MATURITY       LOAN NO    CALL   COLLATERAL  ACCOUNT    OFFICER  INITIALS
<S>                  <C>             <C>           <C>          <C>    <C>         <C>        <C>      <C>
  $1,503,985.26      06-07-1999      10-01-2001    3400269949    11                 111721      791
</TABLE>

  References in the shaded area are for Lender's use only and do not limit the
         applicability of this document to any particular loan or item.

<TABLE>
<S>                                                        <C>
BORROWER: BIOSOURCE TECHNOLOGIES, INC.          LENDER:    SIERRAWEST BANK
          (TIN: 77-0154648)                                CENTRAL PACIFIC REGION
          3333 VACA VALLEY PARKWAY, SUITE 1000             1100 TEXAS ST
          VACAVILLE, CA 95688-9412                         FAIRFIELD, CA 94533
</TABLE>

LOAN TYPE. This is a Variable Rate (at Prime rate as published in the western
edition of the Wall Street Journal, making an initial rate of 7.750%),
Installment Loan to a Corporation for $1,503,985.26 due on October 1, 2001.

PRIMARY PURPOSE OF LOAN. The primary purpose of this loan is for:

    [ ]     Personal, Family, or Household Purposes or Personal Investment.

    [X]     Business (Including Real Estate Investment).

SPECIFIC PURPOSE. The specific purpose of this loan is: TERM OUT BALANCE AS OF
05/28/99 ON LINE OF CREDIT.

DISBURSEMENT INSTRUCTIONS. Borrower understands that no loan proceeds will be
disbursed until all of Lender's conditions for making the loan have been
satisfied. Please disburse the loan proceeds of $1,503,985.26 as follows:

<TABLE>
<S>                                                      <C>
        AMOUNT PAID ON BORROWER'S ACCOUNT:               $1,503,985.26
          $1,503,985.26 Payment on Loan # 3400069949
                                                         -------------
               NOTE PRINCIPAL:                           $1,503,985.26
</TABLE>

FINANCIAL CONDITION. BY SIGNING THIS AUTHORIZATION, BORROWER REPRESENTS AND
WARRANTS TO LENDER THAT THE INFORMATION PROVIDED ABOVE IS TRUE AND CORRECT AND
THAT THERE HAS BEEN NO MATERIAL ADVERSE CHANGE IN BORROWER'S FINANCIAL CONDITION
AS DISCLOSED IN BORROWER'S MOST RECENT FINANCIAL STATEMENT TO LENDER. THIS
AUTHORIZATION IS DATED JUNE 7,1999.

BORROWER:

BIOSOURCE TECHNOLOGIES, INC.

By: Robert L. Erwin                          By: Michael D. Centron
    --------------------------------------       ------------------------------
    ROBERT L. ERWIN, CHAIRMAN OF THE BOARD       MICHAEL D. CENTRON, TREASURER.

<PAGE>   59

                                 PROMISSORY NOTE
================================================================================

<TABLE>
<CAPTION>
PRINCIPAL             LOAN DATE       MATURITY      LOAN NO     CALL    COLLATERAL  ACCOUNT   OFFICER  INITIALS
<S>                  <C>             <C>            <C>         <C>     <C>         <C>       <C>      <C>
$640,895.40          02-07-2000      10-01-2001       0002      04A0       210      894071    282475
</TABLE>

  References in the shaded area are for Lender's use only and do not limit the
 applicability of this document to any particular loan or item. Any item above
       containing "***" has been omitted due to text length limitations.

<TABLE>
<S>                                                           <C>
BORROWER:  LARGE SCALE BIOLOGY CORPORATION FORMERLY KNOWN AS  LENDER:  BANK OF THE WEST
           BIOSOURCE TECHNOLOGIES, INC.                                NORTH VALLEY BUSINESS BANKING REGION #078
           3333 VACA VALLEY PARKWAY, SUITE #1000                       1651 RESPONSE ROAD
           VACAVILLE, CA 95688-9421                                    SACRAMENTO, CA 95815
                                                                       (800) 300-8343
</TABLE>

<TABLE>
<S>                           <C>                 <C>
PRINCIPAL AMOUNT:             INITIAL RATE:       DATE OF NOTE:
$640,895.140                  8.750               FEBRUARY 7, 2000
</TABLE>

PROMISE TO PAY. Large Scale Biology Corporation formerly known as Biosource
Technologies, Inc. ("Borrower") promises to pay to BANK OF THE WEST ("Lender"),
or order, in lawful money of the United States of America, the principal amount
of Six Hundred Forty Thousand Eight Hundred Ninety Five & 401100 Dollars
($640,895.40), together with interest on the unpaid principal balance from
February 7, 2000, until paid in full.

PAYMENT. Subject to any payment changes resulting from changes in the Index,
Borrower will pay this loan in 19 payments of $34,535.75 each payment and an
irregular last payment estimated at $34,535.79. Borrower's first payment is due
March 1, 2000, and all subsequent payments are due on the same day of each month
after that. Borrower's final payment will be due on October 1, 2001, and will be
for all principal and all accrued interest not yet paid. Payments include
principal and interest. Unless otherwise agreed or required by applicable law,
payments will be applied first to any unpaid collection costs and any late
charges, then to any unpaid interest, and any remaining amount to principal. The
annual interest rate for this Note is computed on a 365/360 basis; that is, by
applying the ratio of the annual interest rate over a year of 360 days,
multiplied by the outstanding principal balance, multiplied by the actual number
of days the principal balance is outstanding. Borrower will pay Lender at
Lender's address shown above or at such other place as Lender may designate in
writing.

VARIABLE INTEREST RATE. The interest rate on this Note is subject to change from
time to time based on changes in an index which is the Bank of the West Prime
Rate (the "Index"). The Index is not necessarily the lowest rate charged by
Lender on its loans and is set by Lender in its sole discretion. If the Index
becomes unavailable during the term of this loan, Lender may designate a
substitute index after notifying Borrower. Lender will tell Borrower the current
Index rate upon Borrower's request. The interest rate change will not occur more
often than each day. Borrower understands that Lender may make loans based on
other rates as well. The Index currently is 8.750%. The interest rate to be
applied to the unpaid principal balance of this Note will be at a rate equal to
the Index, resulting in an initial rate of 8.750%. NOTICE: Under no
circumstances will the interest rate on this Note be more than the maximum rate
allowed by applicable law. Whenever increases occur in the interest rate,
Lender, at its option, may do one or more of the following: (A) increase
Borrower's payments to ensure Borrower's loan will pay off by its original final
maturity date, (B) increase Borrower's payments to cover accruing interest, (C)
increase the number of Borrower's payments, and (D) continue Borrower's payments
at the same amount and increase Borrower's final payment.

REPAYMENT. Borrower may pay without penalty all or a portion of the amount owed
earlier than it is due. Early payments will not, unless agreed to Lender in
writing, relieve Borrower of Borrower's obligation to continue to make payments
under the payment schedule. Rather, early payments will reduce the principal
balance due and may result in Borrower's making fewer payments. Borrower agrees
not to send Lender payments marked "paid in full", "without recourse", or
similar language. If Borrower sends such a payment, Lender may accept it without
losing any of Lender's rights under this Note, and Borrower will remain
obligated to pay any further amount owed to Lender. All written communications
concerning disputed amounts, including any check or other payment instrument
that indicates that the payment constitutes "payment in full" of the amount owed
or that is tendered with other conditions or limitations or as full satisfaction
of a disputed amount must be mailed or delivered to: BANK OF THE WEST, North
Valley Business Banking Region #078,1651 Response Road, Sacramento, CA 95815.

LATE CHARGE. If a payment is 15 days or more late Borrower will be charged
5.000% of the unpaid portion of the regularly scheduled payment.

INTEREST AFTER DEFAULT. Upon default, including failure to pay upon final
maturity, at Lender's option, and if permitted by applicable law, Lender may add
any unpaid accrued interest to principal and such sum will bear interest
therefrom until paid at the rate provided in this Note (including any increased
rate). Upon Borrower's failure to pay all amounts declared due pursuant to this
section, Lender, at its option, may, if permitted under applicable law, increase
the variable interest rate on this Note to 5.000 percentage points over the
Index.

DEFAULT. Each of the following shall constitute an event of default ("Event of
Default") under this Note:

    PAYMENT DEFAULt. Borrower fails to make any payment when due under this
    Note.

    OTHER DEFAULTS. Borrower fails to comply with or to perform any other term,
    obligation, covenant or condition contained in this Note or in any of the
    related documents or to comply with or to perform any term, obligation,
    covenant or condition contained in any other agreement between Lender and
    Borrower.

    DEFAULT IN FAVOR OF THIRD PARTIES. Borrower or any Grantor defaults under
    any loan, extension of credit, security agreement, purchase or sales
    agreement, or any other agreement, in favor of any other creditor or person
    that may materially affect any of Borrower's property or Borrower's ability
    to repay this Note or perform Borrower's obligations under this Note or any
    of the related documents.

    FALSE STATEMENTS. Any warranty, representation or statement made or
    furnished to Lender by Borrower or on Borrower's behalf under this Note or
    the related documents is false or misleading in any material respect, either
    now or at the time made or furnished or becomes false or misleading at any
    time thereafter.

    INSOLVENCY. The dissolution or termination of Borrower's existence as a
    going business, the insolvency of Borrower, the appointment of a receiver
    for any part of Borrower's property, any assignment for the benefit of
    creditors, any type of creditor workout, or the commencement of any
    proceeding under any bankruptcy or insolvency laws by or against Borrower.

    CREDITOR OR FORFEITURE PROCEEDINGS. Commencement of foreclosure or
    forfeiture proceedings, whether by judicial proceeding, self-help,
    repossession or any other method, by any creditor of Borrower or by any
    governmental agency against any collateral securing the loan. This

<PAGE>   60
                                 PROMISSORY NOTE
                                  (Continued)                             Page 2
================================================================================

    includes a garnishment of any of Borrower's accounts, including deposit
    accounts, with Lender. However, this Event of Default shall not apply if
    there is a good faith dispute by Borrower as to the validity or
    reasonableness of the claim which is the basis of the creditor or forfeiture
    proceeding and if Borrower gives Lender written notice of the creditor or
    forfeiture proceeding and deposits with Lender monies or a surety bond for
    the creditor or forfeiture proceeding, in an amount determined by Lender, in
    its sole discretion, as being an adequate reserve or bond for the dispute.

    EVENTS AFFECTING GUARANTOR. Any of the preceding events occurs with respect
    to any guarantor, endorser, surety, or accommodation party of any of the
    indebtedness or any guarantor, endorser, surety, or accommodation party dies
    or becomes incompetent, or revokes or disputes the validity of, or liability
    under, any guaranty of the indebtedness .

    ADVERSE CHANGE. A material adverse change occurs in Borrower's financial
    condition, or Lender believes the prospect of payment or performance of this
    Note is impaired.

LENDER'S RIGHTS. Upon default, Lender may declare the entire unpaid principal
balance on this Note and all accrued unpaid interest immediately due, and then
Borrower will pay that amount.

ATTORNEYS' FEES; EXPENSES. Lender may hire or pay someone else to help collect
the loan it Borrower does not pay. Borrower also will pay Lender that amount.
This includes, subject to any limits under applicable law, Lender's attorneys'
fees and Lender's legal expenses, whether or not there is a lawsuit, including
attorneys' fees, expenses for bankruptcy proceedings (including efforts to
modify or vacate any automatic stay or injunction), and appeals. Borrower also
will pay any court costs, in addition to all other sums provided by law.

JURY WAIVER. Lender and Borrower hereby waive the right to any jury trial in any
action, proceeding, or counterclaim brought by either Lender or Borrower against
the other.

GOVERNING LAW. This Note will be governed by, construed and enforced in
accordance with federal law and the laws of the State of California. This Note
has been accepted by Lender in the State of California.

CHOICE OF VENUE. If there is a lawsuit, Borrower agrees upon Lender's request to
submit to the jurisdiction of the courts of the State of California, in the
county in which Borrower's following address is located: 3333 Vaca Valley
Parkway, Suite #1000, Vacaville, CA 95688-9421.

COLLATERAL. Borrower acknowledges this Note is secured by a Assignment of
Deposit Account of even date.

CROSS-COLLATERALIZATION. THIS NOTE IS CROSS-COLLATERALIZED WITH NOTE
#894071-0001,0003,0004 AND 0005 BETWEEN LARGE SCALE BIOLOGY CORPORATION FORMERLY
KNOWN AS BIOSOURCE TECHNOLOGIES, INC. AND BANK OF THE WEST,
SUCCESSOR-IN-INTEREST BY MERGER TO SIERRAWEST BANK.

PRIOR NOTE. The Promissory Note dated November 30,1998, in the principal sum of
$5,000,000.00.

GENERAL PROVISIONS. Lender may delay or forgo enforcing any of its rights or
remedies under this Note without losing them. Borrower and any other person who
signs, guarantees or endorses this Note, to the extent allowed by law, waive any
applicable statute of limitations, presentment, demand for payment, and notice
of dishonor. Upon any change in the terms of this Note, and unless otherwise
expressly stated in writing, no party who signs this Note, whether as maker,
guarantor, accommodation maker or endorser, shall be released from liability.
All such parties agree that Lender may renew or extend (repeatedly and for any
length of time) this loan or release any party or guarantor or collateral; or
impair, fail to realize upon or perfect Lender's security interest in the
collateral; and take any other action deemed necessary by Lender without the
consent of or notice to anyone. All such parties also agree that Lender may
modify this loan without the consent of or notice to anyone other than the party
with whom the modification is made. The obligations under this Note are joint
and several. -

PRIOR TO SIGNING THIS NOTE, BORROWER READ AND UNDERSTOOD ALL THE PROVISIONS OF
THIS NOTE, INCLUDING THE VARIABLE INTEREST RATE PROVISIONS. BORROWER AGREES TO
THE TERMS OF THE NOTE.

BORROWER ACKNOWLEDGES RECEIPT OF A COMPLETED COPY OF THIS PROMISSORY NOTE.

BORROWER:

LARGE SCALE BIOLOGY CORPORATION FORMERLY KNOWN AS BIOSOURCE TECHNOLOGIES, INC.

<TABLE>
<S>                                                       <C>
By:    Robert L. Erwin                                    By:    Michael D. Centron
       -----------------------------------------------           --------------------------------------------
       Robert L. Erwin, Chairman of the Board of Large           Michael D. Centron, Chairman of the Board of
       Scale Biology Corporation formerly known as               Large Scale Biology Corporation formerly
       Biosource Technologies, Inc.                              known as Biosource Technologies, Inc.

By:    John S. Rakita
       -----------------------------------------------
       John S. Rakitan, Secretary of Large Scale
       Biology Corporation formerly known as Biosource
       Technologies, Inc.
</TABLE>

<PAGE>   61
                              CORPORATE RESOLUTION

<TABLE>
<CAPTION>
    PRINCIPAL         LOAN DATE       MATURITY      LOAN NO     CALL    COLLATERAL  ACCOUNT   OFFICER  INITIALS
<S>                  <C>             <C>            <C>         <C>     <C>         <C>       <C>      <C>
   $640,895.40       02-07-2000      10-01-2001       0002      04A0       210      894071    282475
</TABLE>

  References in the shaded area are for Lender's use only and do not limit the
 applicability of this document to any particular loan or item. Any item above
       containing "***" has been omitted due to text length limitations.

<TABLE>
<S>                                                              <C>
CORPORATION: LARGE SCALE BIOLOGY CORPORATION FORMERLY KNOWN AS   LENDER: BANK OF THE WEST
             BIOSOURCE TECHNOLOGIES, INC.                                NORTH VALLEY BUSINESS BANKING REGION #078
             3333 VACA VALLEY PARKWAY, SUITE #1000                       1651 RESPONSE ROAD
             VACAVILLE, CA 95688-9421                                    SACRAMENTO, CA 95815
                                                                         (800) 300-8343
</TABLE>

I, THE UNDERSIGNED, DO HEREBY CERTIFY THAT:

THE CORPORATION'S EXISTENCE. The complete and correct name of the Corporation is
Large Scale Biology Corporation formerly known as Biosource Technologies, Inc.
("Corporation"). The Corporation is a corporation for profit which is, and at
all times shall be, duly organized, validly existing, and in good standing under
and by virtue of the laws of the State of California. The Corporation is duly
authorized to transact business in all other states in which the Corporation is
doing business, having obtained all necessary filings, governmental licenses and
approvals for each state in which the Corporation is doing business.
Specifically, the Corporation is, and at all times shall be, duly qualified as a
foreign corporation in all states in which the failure to so qualify would have
a material adverse effect on its business or financial condition. The
Corporation has the full power and authority to own its properties and to
transact the business in which it is presently engaged or presently proposes to
engage. The Corporation maintains an office at 3333 Vaca Valley Parkway, Suite
#1000, Vacaville, CA 95688-9421. Unless the Corporation has designated otherwise
in writing, the principal office is the office at which the Corporation keeps
its books and records. The Corporation will notify Lender of any change in the
location of the Corporation's principal office. The Corporation shall do all
things necessary to preserve and to keep in full force and effect its existence,
rights and privileges, and shall comply with all regulations, rules, ordinances,
statutes, orders and decrees of any governmental or quasi-governmental authority
or court applicable to the Corporation and the Corporation's business
activities.

RESOLUTIONS ADOPTED. At a meeting of the Directors of the Corporation, or if the
Corporation is a close corporation having no Board of Directors then at a
meeting of the Corporation's shareholders, duly called and held on October 16,
1998, at which a quorum was present and voting, or by other duly authorized
action in lieu of a meeting, the resolutions set forth in this Resolution Were
adopted.

OFFICERS. The following named persons are officers of Large Scale Biology
Corporation formerly known as Biosource Technologies, Inc.:

<TABLE>
<CAPTION>
           NAMES                        TITLES                   AUTHORIZED              ACTUAL SIGNATURES
           -----                        ------                   ----------              -----------------
<S>                           <C>                                <C>                 <C>
Robert L. Erwin               Chairman of the Board                   Y              Robert L. Erwin

Michael D. Centron            Treasurer                               Y              Michael D. Centron

John S. Rakitan               Secretary                               Y              John S. Rakitan
</TABLE>

ACTIONS AUTHORIZED. Any two (2) of the authorized persons listed above may enter
into any agreements of any nature with Lender, and those of agreements will bind
the Corporation. Specifically, but without limitation, any J2) of such
authorized persons are authorized, empowered, and directed to do the following
for and on behalf of the Corporation:

    BORROW MONEY. To borrow from time to time from Lender, on such terms as may
    be agreed upon between the Corporation and Lender, such sum or sums of money
    as in their judgment should be borrowed, without limitation.

    EXECUTE NOTES. To execute and deliver to Lender the promissory note or
    notes, or other evidence of the Corporation's credit accommodations, on
    Lender's forms, at such rates of interest and on such terms as may be agreed
    upon, evidencing the sums of money so borrowed or any of the Corporation's
    indebtedness to Lender, and also to execute and deliver to Lender one or
    more renewals, extensions, modifications, refinancings, consolidations, or
    substitutions for one or more of the notes, any portion of the notes, or any
    other evidence of credit accommodations.

    GRANT SECURITY. To mortgage, pledge, transfer, endorse, hypothecate, or
    otherwise encumber and deliver to Lender any property now or hereafter
    belonging to the Corporation or in which the Corporation now or hereafter
    may have an interest, including without limitation all real property and all
    personal property (tangible or intangible) of the Corporation, as security
    for the payment of any loans or credit accommodations so obtained, any
    promissory notes so executed (including any amendments to or modifications,
    renewals, and extensions of such promissory notes), or any other or further
    indebtedness of the Corporation to Lender at any time owing, however the
    same may be evidenced. Such property may be mortgaged, pledged, transferred,
    endorsed, hypothecated or encumbered at the time such loans are obtained or
    such indebtedness is incurred, or at any other time or times, and may be
    either in addition to or in lieu of any property theretofore mortgaged,
    pledged, transferred, endorsed, hypothecated or encumbered.

    EXECUTE SECURITY DOCUMENTS. To execute and deliver to Lender the forms of
    mortgage, deed of trust, pledge agreement, hypothecation agreement, and
    other security agreements and financing statements which Lender may require
    and which shall evidence the terms and conditions under and pursuant to
    which such liens and encumbrances, or any of them, are given; and also to
    execute and deliver to Lender any other written instruments, any chattel
    paper, or any other collateral, of any kind or nature, which Lender may deem
    necessary or proper in connection with or pertaining to the giving of the
    liens and encumbrances. Notwithstanding the foregoing, any one of the above
    authorized persons may execute, deliver, or record financing statements.

    NEGOTIATE ITEMS. To draw, endorse, and discount with Lender all drafts,
    trade acceptances, promissory notes, or other evidences of indebtedness
    payable to or belonging to the Corporation or in which the Corporation may
    have an interest, and either to receive cash for the same or to cause such
    proceeds to be credited to the Corporation's account with Lender, or to
    cause such other disposition of the proceeds derived therefrom as they may
    deem advisable.

    FURTHER ACTS. In the case of lines of credit, to designate additional or
    alternate individuals as being authorized to request advances under such
    lines, and in all cases, to do and perform such other acts and things, to
    pay any and all fees and costs, and to execute and deliver such other

<PAGE>   62
                              CORPORATE RESOLUTION
                                  (CONTINUED)                             PAGE 2
================================================================================

    documents and agreements, including agreements waiving the right to a trial
    by jury, as the officers may in their discretion deem reasonably necessary
    or proper in order to carry into effect the provisions of this Resolution.

ASSUMED BUSINESS NAMES. The Corporation has filed or recorded all documents or
filings required by law relating to all assumed business names used by the
Corporation. Excluding the name of the Corporation, the following is a complete
list of all assumed business names under which the Corporation does business:
None.

NOTICES TO LENDER. The Corporation will notify Lender in writing at Lender's
address shown above (or such other addresses as Lender may designate from time
to time) prior to any (A) change in the Corporation's name, (B) change in the
Corporation's assumed business name(s), (C) change in the management of the
Corporation, (D) change in the authorized signer(s), (E) change in the
Corporation's principal office address, (F) conversion of the Corporation to a
new or different type of business entity, or (G) change in any other aspect of
the Corporation that directly or indirectly relates to any agreements between
the Corporation and Lender. No change in the Corporation's name will take effect
until after Lender has been notified.

CERTIFICATION CONCERNING OFFICERS AND RESOLUTIONS. The officers named above are
duly elected, appointed, or employed by or for the Corporation, as the case may
be, and occupy the positions set opposite their respective names. This
Resolution now stands of record on the books of the Corporation, is in full
force and effect, and has not been modified or revoked in any manner whatsoever.

NO CORPORATE SEAL. The Corporation has no corporate seal, and therefore, no seal
is affixed to this Resolution.

CONTINUING VALIDITY. Any and all acts authorized pursuant to this Resolution and
performed prior to the passage of this Resolution are hereby ratified and
approved. This Resolution shall be continuing, shall remain in full force and
affect and Lender may rely on it until written notice of its revocation shall
have been delivered to and received by Lender at Lender's address shown above
(or such addresses as Lender may designate from time to time). Any such notice
shall not affect any of the Corporation's agreements or commitments in effect at
the time notice is given.

IN TESTIMONY WHEREOF, I have hereunto set my hand.

I have read all the provisions of this Resolution, and I personally and on
behalf of the Corporation certify that all statements and representations made
in this Resolution are true and correct. This Corporate Resolution is dated
October 16, 1998.

                                CERTIFIED TO AND ATTESTED BY:

                                By  John S. Ratikan
                                    -------------------------------
                                     John S. Ratikan, Secretary

                                By:
                                    -------------------------------
                                       Authorized Signer

NOTE: If the officers signing this Resolution are designated by the foregoing
document as one of the officers authorized to act on the Corporation's behalf,
it is advisable to have this Resolution signed by at least one non-authorized
officer of the Corporation.

<PAGE>   63
                     DISBURSEMENT REQUEST AND AUTHORIZATION

<TABLE>
<CAPTION>
    PRINCIPAL         LOAN DATE       MATURITY      LOAN NO     CALL    COLLATERAL  ACCOUNT   OFFICER  INITIALS
<S>                  <C>             <C>            <C>         <C>     <C>         <C>       <C>      <C>
   $640,895.40       02-07-2000      10-01-2001       0002      04A0       210      894071    282475
</TABLE>

  References in the shaded area are for Lender's use only and do not limit the
 applicability of this document to any particular loan or item. Any item above
       containing "***" has been omitted due to text length limitations.

<TABLE>
<S>                                                           <C>
BORROWER: LARGE SCALE BIOLOGY CORPORATION FORMERLY KNOWN AS   LENDER: BANK OF THE WEST
          BIOSOURCE TECHNOLOGIES, INC.                                NORTH VALLEY BUSINESS BANKING
          3333 VACA VALLEY PARKWAY, SUITE #1000                       1651 RESPONSE ROAD
          VACAVILLE, CA 95688-9421                                    SACRAMENTO, CA 95815
                                                                      (800) 300-8343
</TABLE>

LOAN TYPE. This is a Variable Rate Nondisclosable Loan to a Corporation for
$640,895.40 due on October 1, 2001. The reference rate (Bank of the West Prime
Rate, currently 8.750%) resulting in an initial rate of 8.750.

PRIMARY PURPOSE OF LOAN. The primary purpose of this loan is for (please
initial):

         [ ]    Personal, Family, or Household Purposes or Personal Investment.

         [X]    Business (Including Real Estate Investment).

SPECIFIC PURPOSE. The specific purpose of this loan is: Term-out line of credit
#894071-002.

DISBURSEMENT INSTRUCTIONS. Borrower understands that no loan proceeds will be
disbursed until all of Lender's conditions for making the loan have been
satisfied. Please disburse the loan proceeds of $640,895.40 as follows:

<TABLE>
<S>                                                          <C>
               Amount paid on Borrower's account:            $640,895.40
                 Payment on Loan # 894071-0002
                                                             -----------
               Note Principal:                               $640,895.40
</TABLE>

AUTOMATIC PAYMENTS. Borrower hereby authorizes Lender automatically to deduct
from Borrower's account numbered ******** the amount of any loan payment. If
the funds in the account are insufficient to cover any payment, Lender shall not
be obligated to advance funds to cover the payment. At any time and for any
reason, Borrower or Lender may voluntarily terminate Automatic Payments.

FINANCIAL CONDITION. BY SIGNING THIS AUTHORIZATION, BORROWER REPRESENTS AND
WARRANTS TO LENDER THAT THE INFORMATION PROVIDED ABOVE IS TRUE AND CORRECT AND
THAT THERE HAS BEEN NO MATERIAL ADVERSE CHANGE IN BORROWER'S FINANCIAL CONDITION
AS DISCLOSED IN BORROWER'S MOST RECENT FINANCIAL STATEMENT TO LENDER. THIS
AUTHORIZATION IS DATED FEBRUARY 7,2000.

BORROWER:

LARGE SCALE BIOLOGY CORPORATION FORMERLY KNOWN AS BIOSOURCE TECHNOLOGIES, INC.

<TABLE>
<S>                                                       <C>
By:     /s/ Robert L. Erwin                               By:     Michael D. Centron
       -----------------------------------------------           --------------------------------------------
       Robert L. Erwin, Chairman of the Board of Large           Michael D. Centron, Chairman of the Board of
       Scale Biology Corporation formerly known as               Large Scale Biology Corporation formerly
       Biosource Technologies, Inc.                              known as Biosource Technologies, Inc.

By:    John S. Rakita
       -----------------------------------------------
       John S. Rakitan, Secretary of Large Scale
       Biology Corporation formerly known as Biosource
       Technologies, Inc.
</TABLE>

<PAGE>   64
                          ASSIGNMENT OF DEPOSIT ACCOUNT

<TABLE>
<CAPTION>
    PRINCIPAL         LOAN DATE       MATURITY      LOAN NO     CALL    COLLATERAL  ACCOUNT   OFFICER  INITIALS
<S>                  <C>             <C>            <C>         <C>     <C>         <C>       <C>      <C>
   $640,895.40       02-07-2000      10-01-2001       0002      04A0       210      894071    282475
</TABLE>

  References in the shaded area are for Lender's use only and do not limit the
 applicability of this document to any particular loan or item. Any item above
       containing "***" has been omitted due to text length limitations.

<TABLE>
<S>                                                          <C>
GRANTOR: LARGE SCALE BIOLOGY CORPORATION FORMERLY KNOWN AS   LENDER: BANK OF THE WEST
         BIOSOURCE TECHNOLOGIES, INC.                                NORTH VALLEY BUSINESS BANKING REGION #078
         3333 VACA VALLEY PARKWAY, SUITE #1000                       1651 RESPONSE ROAD
         VACAVILLE, CA 95688-9421                                    SACRAMENTO, CA 95815
                                                                     (800) 300-8343
</TABLE>

THIS ASSIGNMENT OF DEPOSIT ACCOUNT dated February 7, 2000, is made and executed
between Large Scale Biology Corporation formerly known as Biosource
Technologies, Inc. ("Grantor") and BANK OF THE WEST ("Lender").

ASSIGNMENT. For valuable consideration, Grantor assigns and grants to Lender a
security interest in the Collateral, including without limitation the deposit
accounts described below, to secure the Indebtedness and agrees that Lender
shall have the rights stated in this Agreement with respect to the Collateral,
in addition to all other rights which Lender may have by law.

COLLATERAL. The word "Collateral" means the following described deposit account
("Account").

    CD Account Number 250-853736 with Lender with an approximate balance of
    $1,239,776.71

together with (A) all interest, whether now accrued or hereafter accruing; (B)
all additional deposits hereafter made to the Account; (C) any and all proceeds
from the Account; and (D) all renewals, replacements and substitutions for any
of the foregoing.

CROSS-COLLATERALIZATION. In addition to the Note, this Agreement secures all
obligations, debts and liabilities, plus interest thereon, of Grantor to Lender,
or any one or more of them, as well as all claims by Lender against Grantor or
any one or more of them, whether now existing or hereafter arising, whether
related or unrelated to the purpose of the Note, whether voluntary or otherwise,
whether due or not due, direct or indirect, absolute or contingent, liquidated
or unliquidated and whether Grantor may be liable individually or jointly with
others, whether obligated as guarantor, surety, accommodation party or
otherwise, and whether recovery upon such amounts may be or hereafter may become
barred by any statute of limitations, and whether the obligation to repay such
amounts may be or hereafter may become otherwise unenforceable. (Initial Here
_______________ )

GRANTOR'S REPRESENTATIONS AND WARRANTIES WITH RESPECT TO THE COLLATERAL. With
respect to the Collateral, Grantor represents and warrants to Lender that:

    OWNERSHIP. Grantor is the lawful owner of the Collateral free and clear of
    all loans, liens, encumbrances, and claims except as disclosed to and
    accepted by Lender in writing.

    RIGHT TO GRANT SECURITY INTEREST. Grantor has the full right, power, and
    authority to enter into this Agreement and to assign the Collateral to
    Lender.

    NO PRIOR ASSIGNMENT. Grantor has not previously granted a security interest
    in the Collateral to any other creditor.

    NO DEFAULTS. There are no defaults relating to the Collateral, and there are
    no offsets or counterclaims to the same. Grantor will strictly and promptly
    do everything required of Grantor under the terms, conditions, promises, and
    agreements contained in or relating to the Collateral. Validity; Binding
    Effect. This Agreement is binding upon Grantor and Grantor's successors and
    assigns and is legally enforceable in accordance with its terms.

LENDER'S RIGHTS AND OBLIGATIONS WITH RESPECT TO THE COLLATERAL. While this
Agreement is in effect, Lender may retain the rights to possession of the
Collateral, together with any and all evidence of the Collateral, such as
certificates or passbooks. This Agreement will remain in effect until (a) there
no longer is any Indebtedness owing to Lender; (b) all other obligations secured
by this Agreement have been fulfilled; and (c) Grantor, in writing, has
requested from Lender a release of this Agreement.

LENDER'S EXPENDITURES. If any action or proceeding is commenced that would
materially affect Lender's interest in the Collateral or if Grantor fails to
comply with any provision of this Agreement or any Related Documents, including
but not limited to Grantor's failure to discharge or pay when due any amounts
Grantor is required to discharge or pay under this Agreement or any Related
Documents, Lender on Grantor's behalf may (but shall not be obligated to) take
any action that Lender deems appropriate, including but not limited to
discharging or paying all taxes, liens, security interests, encumbrances and
other claims, at any time levied or placed on the Collateral and paying all
costs for insuring, maintaining and preserving the Collateral All such
expenditures incurred or paid by Lender for such purposes will then bear
interest at the rate charged under the Note from the date incurred or paid by
Lender to the date of repayment by Grantor. All such expenses will become a part
of the Indebtedness and, at Lender's option, will (A) be payable on demand; (13)
be added to the balance of the Note and be apportioned among and be payable with
any installment payments to become due during either (1) the term of any
applicable insurance policy; or (2) the remaining term of the Note; or (C) be
treated as a balloon payment which will be due and payable at the Note's
maturity. The Collateral also will secure payment of these amounts. Such right
shall be in addition to all other rights and remedies to which Lender may be
entitled upon Default.

LIMITATIONS ON OBLIGATIONS OF LENDER. Lender shall use ordinary reasonable care
in the physical preservation and custody of any certificate or passbook for the
Collateral but shall have no other obligation to protect the Collateral or its
value. In particular, but without limitation, Lender shall have no
responsibility (A) for the collection or protection of any income on the
Collateral; (13) for the preservation of rights against issuers of the
Collateral or against third persons; (C) for ascertaining any maturities,
conversions, exchanges, offers, tenders, or similar matters relating to the
Collateral; nor (D) for informing the Grantor about any of the above, whether or
not Lender has or is deemed to have knowledge of such matters.

DEFAULT. Each of the following shall constitute an Event of Default under this
Agreement:

    PAYMENT DEFAULT. Grantor fails to make any payment when due under the
    Indebtedness.

<PAGE>   65
                          ASSIGNMENT OF DEPOSIT ACCOUNT
                                  (CONTINUED)                             PAGE 2
================================================================================

    OTHER DEFAULTS. Grantor fails to comply with or to perform any other term,
    obligation, covenant or condition contained in this Agreement or in any of
    the Related Documents or to comply with or to perform any term, obligation,
    covenant or condition contained in any other agreement between Lender and
    Grantor.

    DEFAULT IN FAVOR OF THIRD PARTIES. Should Grantor or any Grantor default
    under any loan, extension of credit, security agreement, purchase or sales
    agreement, or any other agreement, in favor of any other creditor or person
    that may materially affect any of Grantor's property or Grantor's or any
    Grantor's ability to repay the Indebtedness or perform their respective
    obligations under this Agreement or any of the Related Documents.

    FALSE STATEMENTS. Any warranty, representation or statement made or
    furnished to Lender by Grantor or on Grantor's behalf under this Agreement,
    the Note, or the Related Documents is false or misleading in any material
    respect, either now or at the time made or furnished or becomes false or
    misleading at any time thereafter.

    DEFECTIVE COLLATERALIZATION. This Agreement or any of the Related Documents
    ceases to be in full force and effect (including failure of any collateral
    document to create a valid and perfected security interest or lien) at any
    time and for any reason.

    INSOLVENCY. The dissolution or termination of Grantor's existence as a going
    business, the insolvency of Grantor, the appointment of a receiver for any
    part of Grantor's property, any assignment for the benefit of creditors, any
    type of creditor workout, or the commencement of any proceeding under any
    bankruptcy or insolvency laws by or against Grantor.

    CREDITOR OR FORFEITURE PROCEEDINGS. Commencement of foreclosure or
    forfeiture proceedings, whether by judicial proceeding, self-help,
    repossession or any other method, by any creditor of Grantor or by any
    governmental agency against any collateral securing the Indebtedness. This
    includes a garnishment of any of Grantor's accounts, including deposit
    accounts, with Lender. However, this Event of Default shall not apply if
    there is a good faith dispute by Grantor as to the validity or
    reasonableness of the claim which is the basis of the creditor or forfeiture
    proceeding and if Grantor gives Lender written notice of the creditor or
    forfeiture proceeding and deposits with Lender monies or a surety bond for
    the creditor or forfeiture proceeding, in an amount determined by Lender, in
    its sole discretion, as being an adequate reserve or bond for the dispute.

    EVENTS AFFECTING GUARANTOR. Any of the preceding events occurs with respect
    to guarantor, endorser, surety, or accommodation party of any of the
    Indebtedness or guarantor, endorser, surety, or accommodation party dies or
    becomes incompetent.

    ADVERSE CHANGE. A material adverse change occurs in Grantor's financial
    condition, or Lender believes the prospect of payment or performance of the
    Indebtedness is impaired.

    INSECURITY. Lender in good faith believes itself insecure.

RIGHTS AND REMEDIES ON DEFAULT. Upon the occurrence of an Event of Default, or
at any time thereafter, Lender may exercise any one or more of the following
rights and remedies, in addition to any rights or remedies that may be available
at law, in equity, or otherwise:

    ACCELERATE INDEBTEDNESS. Lender may declare all Indebtedness of Grantor to
    Lender immediately due and payable, without notice of any kind to Grantor.

    APPLICATION OF ACCOUNT PROCEEDS. Lender may take directly all funds in the
    Account and apply them to the Indebtedness. If the Account is subject to an
    early withdrawal penalty, that penalty shall be deducted from the Account
    before its application to the Indebtedness, whether the Account is with
    Lender or some other institution. Any excess funds remaining after
    application of the Account proceeds to the Indebtedness will be paid to
    Grantor as the interests of Grantor may appear. Grantor agrees, to the
    extent permitted by law, to pay any deficiency after application of the
    proceeds of the Account to the Indebtedness. Lender also shall have all the
    rights of a secured party under the California Uniform Commercial Code, even
    if the Account is not otherwise subject to such Code concerning security
    interests, and the parties to this Agreement agree that the provisions of
    the Code giving rights to a secured party shall nonetheless be a part of
    this Agreement.

    OTHER RIGHTS AND REMEDIES. Lender shall have and may exercise any or all of
    the rights and remedies of a secured creditor under the provisions of the
    California Uniform Commercial Code, at law, in equity, or otherwise.

    DEFICIENCY JUDGMENT. If permitted by applicable law, Lender may obtain a
    judgment for any deficiency remaining in the Indebtedness due to Lender
    after application of all amounts received from the exercise of the rights
    provided in this section.

    ELECTION OF REMEDIES. Except as may be prohibited by applicable law, all of
    Lender's rights and remedies, whether evidenced by this Agreement or by any
    other writing, shall be cumulative and may be exercised singularly or
    concurrently. Election by Lender to pursue any remedy will not bar any other
    remedy, and an election to make expenditures or to take action to perform an
    obligation of Grantor under this Agreement, after Grantor's failure to
    perform, shall not affect Lender's right to declare a default and exercise
    its remedies.

    CUMULATIVE REMEDIES. All of Lender's rights and remedies, whether evidenced
    by this Agreement or by any other writing, shall be cumulative and may be
    exercised singularly or concurrently. Election by Lender to pursue any
    remedy shall not exclude pursuit of any other remedy, and an election to
    make expenditures or to take action to perform an obligation of Grantor
    under this Agreement, after Grantor's failure to perform, shall not affect
    Lender's right to declare a default and to exercise its remedies.

MISCELLANEOUS PROVISIONS. The following miscellaneous provisions are a part of
this Agreement:

    AMENDMENTS. This Agreement, together with any Related Documents, constitutes
    the entire understanding and agreement of the parties as to the matters set
    forth in this Agreement. No alteration of or amendment to this Agreement
    shall be effective unless given in writing and signed by the party or
    parties sought to be charged or bound by the alteration or amendment.

    ATTORNEYS' FEES; EXPENSES. Grantor agrees to pay upon demand all of Lender's
    costs and expenses, including Lender's attorneys' fees and Lender's legal
    expenses, incurred in connection with the enforcement of this Agreement.
    Lender may hire or pay someone else to help enforce this Agreement, and
    Grantor shall pay the costs and expenses of such enforcement. Costs and
    expenses include Lender's attorneys' fees and legal expenses whether or not
    there is a lawsuit, including attorneys' fees and legal expenses for
    bankruptcy proceedings (including efforts to modify or vacate any automatic
    stay or injunction), appeals, and any anticipated post-judgment collection
    services. Grantor also shall pay all court costs and such additional fees as
    may be directed by the court.

    CAPTION HEADINGS. Caption headings in this Agreement are for convenience
    purposes only and are not to be used to interpret or define the provisions
    of this Agreement.

<PAGE>   66
                          ASSIGNMENT OF DEPOSIT ACCOUNT
                                  (CONTINUED)                             PAGE 3
================================================================================

    GOVERNING LAW. This Agreement will be governed by, construed and enforced in
    accordance with federal law and the laws of the State of California. This
    Agreement has been accepted by Lender in the State of California.

    CHOICE OF VENUE. If there is a lawsuit, Grantor agrees upon Lender's request
    to submit to the jurisdiction of the courts of the State of California, in
    the county in which Grantor's following address is located: 3333 Vaca Valley
    Parkway, Suite #1000, Vacaville, CA 95688-9421.

    PREFERENCE PAYMENTS. Any monies Lender pays because of an asserted
    preference claim in Grantor's bankruptcy will become a part of the
    Indebtedness and, at Lender's option, shall be payable by Grantor as
    provided in this Agreement.

    NO WAIVER BY LENDER. Lender shall not be deemed to have waived any rights
    under this Agreement unless such waiver is given in writing and signed by
    Lender. No delay or omission on the part of Lender in exercising any right
    shall operate as a waiver of such right or any other right. A waiver by
    Lender of a provision of this Agreement shall not prejudice or constitute a
    waiver of Lender's right otherwise to demand strict compliance with that
    provision or any other provision of this Agreement. No prior waiver by
    Lender, nor any course of dealing between Lender and Grantor, shall
    constitute a waiver of any of Lender's rights or of any of Grantor's
    obligations as to any future transactions. Whenever the consent of Lender is
    required under this Agreement, the granting of such consent by Lender in any
    instance shall not constitute continuing consent to subsequent instances
    where such consent is required and in all cases such consent may be granted
    or withheld in the sole discretion of Lender.

    NOTICES. Any notice required to be given under this Agreement shall be given
    in writing, and shall be effective when actually delivered, when actually
    received by telefacsimile (unless otherwise required by law), when deposited
    with a nationally recognized overnight courier, or, it mailed, when
    deposited in the United States mail, as first class, certified or registered
    mail postage prepaid, directed to the addresses shown near the beginning of
    this Agreement. Any party may change its address for notices under this
    Agreement by giving formal written notice to the other parties, specifying
    that the purpose of the notice is to change the party's address. For notice
    purposes, Grantor agrees to keep Lender informed at all times of Grantor's
    current address. Unless otherwise provided or required by law, if there is
    more than one Grantor, any notice given by Lender to any Grantor is deemed
    to be notice given to all Grantors.

    POWER OF ATTORNEY. Grantor hereby appoints Lender as its true and lawful
    attorney- i n-fact, irrevocably, with full power of substitution to do the
    following: (a) to demand, collect, receive, receipt for, sue and recover all
    sums of money or other property which may now or hereafter become due, owing
    or payable from the Collateral; (b) to execute, sign and endorse any and all
    claims, instruments, receipts, checks, drafts or warrants issued in payment
    for the Collateral; (c) to settle or compromise any and all claims arising
    under the Collateral, and, in the place and stead of Grantor, to execute and
    deliver its release and settlement for the claim; and (d) to file any claim
    or claims or to take any action or institute or take part in any
    proceedings, either in its own name or in the name of Grantor, or otherwise,
    which in the discretion of Lender may seem to be necessary or advisable.
    This power is given as security for the Indebtedness, and the authority
    hereby conferred is and shall be irrevocable and shall remain in full force
    and effect until renounced by Lender.

    WAIVER OF CO-OBLIGOR'S RIGHTS. If more than one person is obligated for the
    Indebtedness, Grantor irrevocably waives, disclaims and relinquishes all
    claims against such other person which Grantor has or would otherwise have
    by virtue of payment of the Indebtedness or any part thereof, specifically
    including but not limited to all rights of indemnity, contribution or
    exoneration.

    SEVERABILITY. If a court of competent jurisdiction finds any provision of
    this Agreement to be illegal, invalid, or unenforceable as to any
    circumstance, that finding shall not make the offending provision illegal,
    invalid, or unenforceable as to any other circumstance. It feasible, the
    offending provision shall be considered modified so that it becomes legal,
    valid and enforceable. It the offending provision cannot be so modified, it
    shall be considered deleted from this Agreement. Unless otherwise required
    by law, the illegality, invalidity, or unenforceability of any provision of
    this Agreement shall not affect the legality, validity or enforceability of
    any other provision of this Agreement.

    SUCCESSORS AND ASSIGNS. Subject to any limitations stated in this Agreement
    on transfer of Grantor's interest, this Agreement shall be binding upon and
    inure to the benefit of the parties, their successors and assigns. It
    ownership of the Collateral becomes vested in a person other than Grantor,
    Lender, without notice to Grantor, may deal with Grantor's successors with
    reference to this Agreement and the Indebtedness by way of forbearance or
    extension without releasing Grantor from the obligations of this Agreement
    or liability under the Indebtedness.

    SURVIVAL OF REPRESENTATIONS AND WARRANTIES. All representations, warranties,
    and agreements made by Grantor in this Agreement shall survive the execution
    and delivery of this Agreement, shall be continuing in nature, and shall
    remain in full force and effect until such time as Grantor's Indebtedness
    shall be paid in full.

    TIME IS OF THE ESSENCE. Time is of the essence in the performance of this
    Agreement.

    WAIVE JURY. All parties to this Agreement hereby waive the right to any jury
    trial in any action, proceeding, or counterclaim brought by any party
    against any other party.

DEFINITIONS. The following capitalized words and terms shall have the following
meanings when used in this Agreement. Unless specifically stated .-) the
contrary, all references to dollar amounts shall mean amounts in lawful money of
the United States of America. Words and terms used in the singular shall include
the plural, and the plural shall include the singular, as the context may
require. Words and terms not otherwise defined in this Agreement shall have the
meanings attributed to such terms in the Uniform Commercial Code:

    ACCOUNT. The word "Account" means the deposit account described in the
    "Collateral Description" section.

    AGREEMENT. The word "Agreement' means this Assignment of Deposit Account, as
    this Assignment of Deposit Account may be amended or modified from time to
    time, together with all exhibits and schedules attached to this Assignment
    of Deposit Account from time to time.

    BORROWER. The word "Borrower' means Large Scale Biology Corporation formerly
    known as Biosource Technologies, Inc., and all other persons and entities
    signing the Note in whatever capacity.

    COLLATERAL. The word "Collateral" means all of Grantor's right, title and
    interest in and to all the Collateral as described in the Collateral
    Description section of this Agreement.

    DEFAULT. The word "Default' means the Default set forth in this Agreement in
    the section titled "Default".

    EVENT OF DEFAULT. The words "Event of Default" mean any of the Events of
    Default set forth in this Agreement in the Default section of this
    Agreement.

    GRANTOR. The word "Grantor' means Large Scale Biology Corporation formerly
    known as Biosource Technologies, Inc.

<PAGE>   67
                          ASSIGNMENT OF DEPOSIT ACCOUNT
                                  (CONTINUED)                             PAGE 4
================================================================================

    INDEBTEDNESS. The word "Indebtedness" means the indebtedness evidenced by
    the Note or Related Documents, including all principal and interest together
    with all other indebtedness and costs and expenses for which Grantor is
    responsible under this Agreement or under any of the Related Documents. In
    addition, and without limitation, the term "Indebtedness" includes all
    amounts identified in the Cross-Collateralization and Future Advances
    paragraphs as contained in one or more of the Related Documents.

    LENDER. The word "Lender" means BANK OF THE WEST, its successors and
    assigns.

    NOTE. The word "Note" means the Note executed by Grantor in the principal
    amount of $640,895.40 dated February 7, 2000, together with all renewals of,
    extensions of, modifications of, refinancings of, consolidations of, and
    substitutions for the note or credit agreement.

    RELATED DOCUMENTS. The words "Related Documents" mean all promissory notes,
    credit agreements, loan agreements, environmental agreements, guaranties,
    security agreements, mortgages, deeds of trust, security deeds, collateral
    mortgages, and all other instruments, agreements and documents, whether now
    or hereafter existing, executed in connection with the Indebtedness.

GRANTOR HAS READ AND UNDERSTOOD ALL THE PROVISIONS OF THIS ASSIGNMENT OF DEPOSIT
ACCOUNT AND AGREES TO ITS RMS. THIS AGREEMENT IS DATED FEBRUARY 7, 2000.

GRANTOR:

LARGE SCALE BIOLOGY CORPORATION FORMERLY KNOWN AS BIOSOURCE TECHNOLOGIES, INC.

<TABLE>
<S>                                                       <C>
By:     /s/ Robert L. Erwin                               By:     Michael D. Centron
       -----------------------------------------------           --------------------------------------------
       Robert L. Erwin, Chairman of the Board of Large           Michael D. Centron, Chairman of the Board of
       Scale Biology Corporation formerly known as               Large Scale Biology Corporation formerly
       Biosource Technologies, Inc.                              known as Biosource Technologies, Inc.

By:    John S. Rakita
       -----------------------------------------------
       John S. Rakitan, Secretary of Large Scale
       Biology Corporation formerly known as Biosource
       Technologies, Inc.
</TABLE>

LENDER:

BANK OF THE WEST

-------------------------------
Authorized Signer

<PAGE>   68
                                 PROMISSORY NOTE

<TABLE>
<CAPTION>
    PRINCIPAL         LOAN DATE       MATURITY       LOAN NO     CALL   COLLATERAL  ACCOUNT   OFFICER  INITIALS
<S>                  <C>             <C>           <C>           <C>    <C>         <C>       <C>      <C>
   $954,695.60       09-01-1999      10-01-2001    3400369949     11                111721      791
</TABLE>

  References in the shaded area are for Lender's use only and do not limit the
         applicability of this document to any particular loan or item.

<TABLE>
<S>                                                   <C>
BORROWER: BIOSOURCE TECHNOLOGIES, INC.  (TI N:        LENDER: SIERRAWEST BANK
          77-0154648)                                         CENTRAL PACIFIC REGION
          3333 VACA VALLEY PARKWAY, SUITE 1000                1100 TEXAS ST
          VACAVILLE, CA 95688-9412                            FAIRFIELD, CA 94533
</TABLE>

PRINCIPAL AMOUNT:             INITIAL RATE:            DATE OF NOTE:
$954,695.60                   8.250%                   SEPTEMBER 1, 1999

PROMISE TO PAY. BIOSOURCE TECHNOLOGIES, INC. ("Borrower") promises to pay to
SierraWest Bank ("Lender"), or order, in lawful money of the United States of
America, the principal amount of Nine Hundred Fifty Four Thousand Six Hundred
Ninety Five & 60/100 Dollars ($954,695.60), together with interest on the unpaid
principal balance from September 1, 1999, until paid in full.

PAYMENT. Subject to any payment changes resulting from changes in the Index,
Borrower will pay this loan In 24 payments of $41,747.54 each payment and an
Irregular last payment estimated at $41,747.47. Borrower's first payment is due
October 1, 1999, and all subsequent payments are due on the same day of each
month after that. Borrower's final payment will be due on October 1, 2001, and
will be for all principal and all accrued interest not yet paid. Payments
include principal and interest. The annual interest rate for this Note is
computed on a 365/360 basis; that is, by applying the ratio of the annual
interest rate over a year of 360 days, multiplied by the outstanding principal
balance, multiplied by the actual number of days the principal balance is
outstanding. Borrower will pay Lender at Lender's address shown above or at such
other place as Lender may designate in writing. Unless otherwise agreed or
required by applicable law, payments will be applied first to accrued unpaid
interest, then to principal, and any remaining amount to any unpaid collection
costs and late charges.

VARIABLE INTEREST RATE. The interest rate on this Note is subject to change from
time to time based on changes in an independent index which is the Prime rate as
published in the western edition of the Wall Street Journal (the "Index"). The
Index is not necessarily the lowest rate charged by Lender on its loans. If the
Index becomes unavailable during the term of this loan, Lender may designate a
substitute index after notice to Borrower. Lender wilt tell Borrower the current
Index rate upon Borrower's request. Borrower understands that Lender may make
loans based on other rates as well. The interest rate change will not occur more
often than each DAY. THE INDEX CURRENTLY IS 8.250%. THE INTEREST RATE TO BE
APPLIED TO THE UNPAID PRINCIPAL BALANCE OF THIS NOTE WILL BE AT A RATE EQUAL TO
THE INDEX, RESULTING IN AN INITIAL RATE OF 8.250%. NOTICE: Under no
circumstances will the interest rate on this Note be more than the maximum rate
allowed by applicable law. Whenever increases occur in the interest rate,
Lender, at its option, may do one or more of the following: (a) increase
Borrower's payments to ensure Borrower's loan will pay off by its original final
maturity date, (b) increase Borrower's payments to cover accruing interest, (c)
increase the number of Borrower's payments, and (d) continue Borrower's payments
at the same amount and increase Borrower's final payment.

PREPAYMENT. Borrower may pay without penalty all or a portion of the amount owed
earlier than it is due. Early payments will not, unless agreed to by Lender in
writing, relieve Borrower of Borrower's obligation to continue to make payments
under the payment schedule. Rather, they will reduce the principal balance due
and may result in Borrower making fewer payments.

LATE CHARGE. If a payment is 10 days or more late, Borrower will be charged
5.000% of the regularly scheduled payment or $15.00, whichever is greater.

DEFAULT. Borrower will be in default if any of the following happens: (a)
Borrower fails to make any payment when due. (b) Borrower breaks any promise
Borrower has made to Lender, or Borrower fails to comply with or to perform when
due any other term, obligation, covenant, or condition contained in this Note or
any agreement related to this Note, or in any other agreement or loan Borrower
has with Lender. (c) Borrower defaults under any loan, extension of credit,
security agreement, purchase or sales agreement, or any other agreement, in
favor of any other creditor or person that may materially affect any of
Borrower's property or Borrower's ability to repay this Note or perform
Borrower's obligations under this Note or any of the Related Documents. (d) Any
representation or statement made or furnished to Lender by Borrower or on
Borrower's behalf is false or misleading in any material respect either now or
at the time made or furnished. (e) Borrower becomes insolvent, a receiver is
appointed for any part of Borrower's property, Borrower makes an assignment for
the benefit of creditors, or any proceeding is commenced either by Borrower or
against Borrower under any bankruptcy or insolvency laws. (f) Any creditor tries
to take any of Borrower's property on or in which Lender has a lien or security
interest. This includes a garnishment of any of Borrower's accounts with Lender.
(g) Any guarantor dies or any of the other events described in this default
section occurs with respect to any guarantor of this Note. (h) A material
adverse change occurs in Borrower's financial condition, or Lender believes the
prospect of payment or performance of the Indebtedness is impaired. (i) Lender
in good faith deems itself insecure.

If any default, other than a default in payment, is curable and if Borrower has
not been given a notice of a breach of the same provision of this Note within
the preceding twelve (12) months, it may be cured (and no event of default will
have occurred) if Borrower, after receiving written notice from Lender demanding
cure of such default: (a) cures the default within fifteen (15) days; or (b) if
the cure requires more than fifteen (15) days, immediately initiates steps which
Lender deems in Lender's sole discretion to be sufficient to cure the default
and thereafter continues and completes all reasonable and necessary steps
sufficient to produce compliance as soon as reasonably practical.

LENDER'S RIGHTS. Upon default, Lender may declare the entire unpaid principal
balance on this Note and all accrued unpaid interest immediately due, without
notice, and then Borrower will pay that amount. Upon Borrower's failure to pay
all amounts declared due pursuant to this section, including failure to pay upon
final maturity, Lender, at its option, may also, if permitted under applicable
law, increase the variable interest rate on this Note to 5.000 percentage points
over the Index. Lender may hire or pay someone else to help collect this Note if
Borrower does not pay. Borrower also will pay Lender that amount. This includes,
subject to any limits under applicable law, Lender's attorneys' fees and
Lender's legal expenses whether or not there is a lawsuit, including attorneys'
fees and legal expenses for bankruptcy proceedings (including efforts to modify
or vacate any automatic stay or injunction), appeals, and any anticipated
post-judgment collection services. Borrower also will pay any court costs, in
addition to all other sums provided by law. THIS NOTE HAS BEEN DELIVERED TO
LENDER AND ACCEPTED BY LENDER IN THE STATE OF CALIFORNIA. IF THERE IS A LAWSUIT,
BORROWER AGREES UPON LENDER'S REQUEST TO SUBMIT TO THE JURISDICTION OF THE
COURTS OF NEVADA COUNTY, THE STATE OF CALIFORNIA. THIS NOTE SHALL BE GOVERNED BY
AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF CALIFORNIA.

<PAGE>   69
09-01-1999                       PROMISSORY NOTE
LOAN NO 3400369949                 (CONTINUED)                            PAGE 2
================================================================================

RIGHT OF SETOFF. Borrower grants to Lender a contractual security interest in,
and hereby assigns, conveys, delivers, pledges, and transfers to Lender all
Borrower's right, title and interest in and to, Borrower's accounts with Lender
(whether checking, savings, or some other account), including without limitation
all accounts held jointly with someone else and all accounts Borrower may open
in the future, excluding however all IRA and Keogh accounts, and all trust
accounts for which the grant of a security interest would be prohibited by law.
Borrower authorizes Lender, to the extent permitted by applicable law, to charge
or setoff all sums owing on this Note against any and all such accounts.

COLLATERAL. CERTIFICATE OF DEPOSIT # 2132399 IS TO BE MAINTAINED THROUGHOUT THE
COURSE OF THIS LOAN AND ALL SUBSEQUENT TERM LOANS THAT WILL REPAY THIS LOAN. THE
BALANCE OF THE CERTIFICATE OF DEPOSIT MAY VARY ACCORDING TO THE ADDENDUM TO THE
CREDIT APPROVAL REPORT ATTACHED.

CROSS-COLLATERALIZATION. THIS NOTE IS CROSS-COLLATERALIZED WITH NOTE 3400069949,
3400169949 AND NOTE 3400269949 BETWEEN BIOSOURCE TECHNOLOGIES, INC. AND
SIERRAWEST BANK.

GENERAL PROVISIONS. Lender may delay or forgo enforcing any of its rights or
remedies under this Note without losing them. Borrower and any other person who
signs, guarantees or endorses this Note, to the extent allowed by law, waive any
applicable statute of limitations, presentment, demand for payment, protest and
notice of dishonor. Upon any change in the terms of this Note, and unless
otherwise expressly stated in writing, no party who signs this Note, whether as
maker, guarantor, accommodation maker or endorser, shall be released from
liability. All such parties agree that Lender may renew or extend (repeatedly
and for any length of time) this loan, or release any party or guarantor or
collateral; or impair, fail to realize upon or perfect Lender's security
interest in the collateral; and take any other action deemed necessary by Lender
without the consent of or notice to anyone. All such parties also agree that
Lender may modify this loan without the consent of or notice to anyone other
than the party with whom the modification is made.

PRIOR TO SIGNING THIS NOTE, BORROWER READ AND UNDERSTOOD ALL THE PROVISIONS OF
THIS NOTE, INCLUDING THE VARIABLE INTEREST RATE PROVISIONS. BORROWER AGREES TO
THE TERMS OF THE NOTE AND ACKNOWLEDGES RECEIPT OF A COMPLETED COPY OF THE NOTE.

BORROWER:

BIOSOURCE TECHNOLOGIES, INC.

<TABLE>
<S>                                           <C>
By:  Robert L. Erwin                          By: Michael D. Centron
     --------------------------------------       --------------------------------
     ROBERT L. ERWIN, CHAIRMAN OF THE BOARD       MICHAEL D. CENTRON, TREASURER.
</TABLE>

<PAGE>   70
                     DISBURSEMENT REQUEST AND AUTHORIZATION

<TABLE>
<CAPTION>
    PRINCIPAL         LOAN DATE       MATURITY       LOAN NO     CALL   COLLATERAL  ACCOUNT   OFFICER  INITIALS
<S>                  <C>             <C>           <C>           <C>    <C>         <C>       <C>      <C>
   $954,695.60       09-01-1999      10-01-2001    3400369949     11                111721      791
</TABLE>

  References in the shaded area are for Lender's use only and do not limit the
         applicability of this document to any particular loan or item.

<TABLE>
<S>                                               <C>
BORROWER: BIOSOURCE TECHNOLOGIES, INC.  (TI N:    LENDER: SIERRAWEST BANK
          77-0154648)                                     CENTRAL PACIFIC REGION
          3333 VACA VALLEY PARKWAY, SUITE 1000            1100 TEXAS ST
          VACAVILLE, CA 95688-9412                        FAIRFIELD, CA 94533
</TABLE>

LOAN TYPE. This is a Variable Rate (at Prime rate as published in the western
edition of the Wall Street Journal, making an initial rate of 8.250%),
Installment Loan to a Corporation for $954,695.60 due on October 1, 2001.

PRIMARY PURPOSE OF LOAN. The primary purpose of this loan is for:

     [ ]    Personal, Family, or Household Purposes or Personal Investment.

     [X]    Business (Including Real Estate Investment).

SPECIFIC PURPOSE. The specific purpose of this loan is: TERM OUT BALANCE AS OF
08/31/99 ON LINE OF CREDIT.

DISBURSEMENT INSTRUCTIONS. Borrower understands that no loan proceeds will be
disbursed until all of Lender's conditions for making the loan have been
satisfied. Please disburse the loan proceeds of $954,695.60 as follows:

<TABLE>
<S>                                                         <C>
             AMOUNT PAID ON BORROWER'S ACCOUNT:             $954,695.60
              $954,695.60 Payment on Loan # 3400069949
                                                            -----------
             Note Principal:                                $954,695.60
</TABLE>

FINANCIAL CONDITION. BY SIGNING THIS AUTHORIZATION, BORROWER REPRESENTS AND
WARRANTS TO LENDER THAT THE INFORMATION PROVIDED ABOVE IS TRUE AND CORRECT AND
THAT THERE HAS BEEN NO MATERIAL ADVERSE CHANGE IN BORROWER'S FINANCIAL CONDITION
AS DISCLOSED IN BORROWER'S MOST RECENT FINANCIAL STATEMENT TO LENDER. THIS
AUTHORIZATION IS DATED SEPTEMBER 1, 1999.

BORROWER:

BIOSOURCE TECHNOLOGIES, INC.

By: Robert L. Erwin                          By: Michael D. Centron
    --------------------------------------       -------------------------------
    ROBERT L. ERWIN, CHAIRMAN OF THE BOARD       MICHAEL D. CENTRON, TREASURER.

<PAGE>   71

                                               PROMISSORY NOTE

<TABLE>
<CAPTION>
----------------------------------------------------------------------------------------------------------------
PRINCIPAL             LOAN DATE       MATURITY      LOAN NO     CALL     COLLATERAL    ACCOUNT   OFFICER   INITIALS
<S>                  <C>             <C>          <C>           <C>      <C>           <C>       <C>       <C>
$95,000.00           06-18-1998      06-18-1999   3400069792     10                     111721     274
----------------------------------------------------------------------------------------------------------------
References in the shaded area are for Lender's use only and do not limit the
applicability of this document to any particular loan or item.
----------------------------------------------------------------------------------------------------------------
</TABLE>

<TABLE>
<S>                                               <C>      <C>
BORROWER: BIOSOURCE TECHNOLOGIES, INC.            (TIN:   LENDER:    SIERRAWEST BANK
                                                                     CENTRAL PACIFIC REGION
          77-0154648                                                 1100 TEXAS ST.
          3333 VACA VALLEY PARKWAY, SUITE #1000                      FAIRFIELD, CA 94533
          VACAVILLE, CA 95688-9421
</TABLE>

================================================================================

PRINCIPAL AMOUNT: $95,000.00  INITIAL RATE: 9.500%  DATE OF NOTE: JUNE 18, 1998

PROMISE TO PAY BIOSOURCE TECHNOLOGIES, INC. ("BORROWER") PROMISES TO PAY TO
SIERRAWEST BANK ("LENDER"), OR ORDER, IN LAWFUL MONEY OF THE UNITED STATES OF
AMERICA, THE PRINCIPAL AMOUNT OF NINETY FIVE THOUSAND & 00/100 DOLLARS
($95,000.00) OR SO MUCH AS MAY BE OUTSTANDING, TOGETHER WITH INTEREST ON THE
UNPAID OUTSTANDING PRINCIPAL BALANCE OF EACH ADVANCE. INTEREST SHALL BE
CALCULATED FROM THE DATE OF EACH ADVANCE UNTIL REPAYMENT OF EACH ADVANCE.

PAYMENT. BORROWER WILL PAY THIS LOAN IN ONE PAYMENT OF ALL OUTSTANDING PRINCIPAL
PLUS ALL ACCRUED UNPAID INTEREST ON JUNE 18, 1999. IN ADDITION, BORROWER WILL
PAY REGULAR MONTHLY PAYMENTS OF ACCRUED UNPAID INTEREST BEGINNING JULY 18, 1998,
AND ALL SUBSEQUENT INTEREST PAYMENTS ARE DUE ON THE SAME DAY OF EACH MONTH AFTER
THAT. The annual interest rate for this Note is computed on a 365/360 basis;
that is, by a days the principal balance is outstanding. Borrower will pay
Lender at Lender's address shown above or at such other place as Lender may
designate in writing. Unless otherwise agreed or required by applicable law,
payments will be applied first to accrued unpaid interest, then to principal,
and any remaining amount to any unpaid collection costs and late charges.

VARIABLE INTEREST RATE. The interest rate on this Note is subject to change from
time to time based on changes in an independent index which is the Prime rate as
published in the western edition of the Wall Street Journal (the "Index"). The
Index is not necessarily the lowest rate charged by Lender on its loans. If the
Index becomes unavailable during the term of this loan, Lender may designate a
substitute index after notice to Borrower. Lender will tell Borrower the current
Index rate upon Borrower's request. Borrower understands that Lender may make
loans based on other rates as well. The interest rate change will not occur more
often than each day. THE INDEX CURRENTLY IS 8.500%. THE INTEREST RATE TO BE
APPLIED TO THE UNPAID PRINCIPAL BALANCE OF THIS NOTE WILL BE AT A RATE OF 1.000
PERCENTAGE POINT OVER THE INDEX, RESULTING IN AN INITIAL RATE OF 9.500%. NOTICE:
Under no circumstances will the interest rate on this Note be more than the
maximum rate allowed by applicable law.

REPAYMENT. Borrower may pay without penalty all or a portion of the amount owed
earlier than it is due. Early payments will not, unless agreed to by Lender in
writing, relieve Borrower of Borrower's obligation to continue to make payments
of accrued unpaid interest. Rather, they will reduce the principal balance due.

LATE CHARGE. If a payment is 10 DAYS OR MORE LATE, Borrower will be charged
5.000% OF THE REGULARLY SCHEDULED PAYMENT OR $15.00, WHICHEVER IS GREATER.

DEFAULT. Borrower will be in default it any of the following happens: (a)
Borrower fails to make any payment when due. (b) Borrower breaks any promise
Borrower has made to Lender, or Borrower fails to comply with or to perform when
due any other term, obligation, covenant, or condition contained in this Note or
any agreement related to this Note, or in any other agreement or loan Borrower
has with Lender. (c) Borrower defaults under any loan, extension of credit,
security agreement, purchase or sales agreement, or any other agreement, in
favor of any other creditor or person that may materially affect any of
Borrower's property or Borrower's ability to repay this Note or perform
Borrower's obligations under this Note or any of the Related Documents. (d) Any
representation or statement made or furnished to Lender by Borrower or on
Borrower's behalf is false or misleading in any material respect either now or
at the time made or furnished. (e) Borrower becomes insolvent, a receiver is
appointed for any part of Borrower's property, Borrower makes an assignment for
the benefit of creditors, or any proceeding is commenced either by Borrower or
against Borrower under any bankruptcy or insolvency laws. (f) Any creditor tries
to take any of Borrower's property on or in which Lender has a lien or security
interest. This includes a garnishment of any of Borrower's accounts with Lender.
(g) Any guarantor dies or any of the other events described in this default
section occurs with respect to any guarantor of this Note. (h) A material
adverse change occurs in Borrower's financial condition, or Lender believes the
prospect of payment or performance of the Indebtedness is impaired. (i) Lender
in good faith deems itself insecure.

If any default, other than a default in payment, is curable and if Borrower has
not been given a notice of a breach of the same provision of this Note within
the preceding twelve (12) months, it may be cured (and no event of default will
have occurred) if Borrower, after receiving written notice from Lender demanding
cure of such default: (a) cures the default within fifteen (15) days; or (b) if
the cure requires more than fifteen (15) days, immediately initiates steps which
Lender deems in Lender's sole discretion to be sufficient to cure the default
and thereafter continues and completes all reasonable and necessary steps
sufficient to produce compliance as soon as reasonably practical.

LENDER'S RIGHTS. Upon default, Lender may declare the entire unpaid principal
balance on this Note and all accrued unpaid interest immediately due, without
notice, and then Borrower will pay that amount. Upon Borrower's failure to pay
all amounts declared due pursuant to this section, including failure to pay upon
final maturity, Lender, at its option, may also, if permitted under applicable
law, increase the variable interest rate on this Note to 6.000 percentage points
over the Index. Lender may hire or pay someone else to help collect this Note if
Borrower does not pay. Borrower also will pay Lender that amount. This includes,
subject to any limits under applicable law, Lender's attorneys' fees and
Lender's legal expenses whether or not there is a lawsuit, including attorneys'
fees and legal expenses for bankruptcy proceedings (including efforts to modify
or vacate any automatic stay or injunction), appeals, and any anticipated
post-judgment collection services. Borrower also will pay any court costs, in
addition to all other sums provided by law. THIS NOTE HAS BEEN DELIVERED TO
LENDER AND ACCEPTED BY LENDER IN THE STATE OF CALIFORNIA. IF THERE IS A LAWSUIT,
BORROWER AGREES UPON LENDER'S REQUEST TO SUBMIT TO THE JURISDICTION OF THE
COURTS OF NEVADA COUNTY, THE STATE OF CALIFORNIA. THIS NOTE SHALL BE GOVERNED BY
AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF CALIFORNIA.

RIGHT OF SETOFF. Borrower grants to Lender a contractual security interest in,
and hereby assigns, conveys, delivers, pledges, and transfers to Lender all
Borrower's right, title and interest in and to, Borrower's accounts with Lender
(whether checking, savings, or some other account), including without limitation
all accounts held jointly with someone else and all accounts Borrower may open
in the future, excluding however all IRA and Keogh accounts, and all trust
accounts for which the grant of a security interest would be prohibited by law.
Borrower authorizes Lender, to the extent permitted by applicable law, to charge
or setoff all sums owing on this Note against any and all such accounts.

<PAGE>   72
06-18-1998                  PROMISSORY NOTE
LOAN NO 3400069792            (CONTINUED)                                 PAGE 2
================================================================================

LINE OF CREDIT. This Note evidences a straight line of credit. Once the total
amount of principal has been advanced, Borrower is not entitled to further loan
advances. Advances under this Note may be requested orally by Borrower or by an
authorized person. All oral requests shall be confirmed in writing on the day of
the request. All communications, instructions, or directions by telephone or
otherwise to Lender are to be directed to Lender's office shown above. The
following party or parties are authorized to request advances under the line of
credit until Lender receives from Borrower Eat Lender's address shown above
written notice of revocation of their authority: ROBERT L. ERWIN, PRESIDENT;
MICHAEL D. CENTRON, TREASURER. Borrower agrees to be liable for all sums either:
(a) advanced in accordance with the &R; an' I instructions of an authorized
person or (b) credited to any of Borrower's accounts with Lender. The unpaid
principal balance owing on this Note at any time may be evidenced by
endorsements on this Note or by Lender's internal records, including daily
computer print-outs. Lender will have no obligation to advance funds under this
Note if: (a) Borrower or any guarantor is in default under the terms of this
Note or any agreement that Borrower or any guarantor has with Lender, including
any agreement made in connection with the signing of this Note; (b) Borrower or
any guarantor ceases doing business or is insolvent; (c) any guarantor seeks,
claims or otherwise attempts to limit, modify or revoke such guarantor's
guarantee of this Note or any other loan with Lender; (d) Borrower has applied
funds provided pursuant to this Note for purposes other than those authorized by
Lender; or (e) Lender in good faith deems itself insecure under this Note or any
other agreement between Lender and Borrower.

GENERAL PROVISIONS. Lender may delay or forgo enforcing any of its rights or
remedies under this Note without losing them. Borrower and any other person who
signs, guarantees or endorses this Note, to the extent allowed by law, waive any
applicable statute of limitations, presentment, demand for payment, protest and
notice of dishonor. Upon any change in the terms of this Note, and unless
otherwise expressly stated in writing, no party who signs this Note, whether as
maker, guarantor, accommodation maker or endorser, shall be released from
liability. All such parties agree that Lender may renew or extend (repeatedly
and for any length of time) this loan, or release any party or guarantor or
collateral; or impair, fail to realize upon or perfect Lender's security
interest in the collateral; and take any other action deemed necessary by Lender
without the consent of or notice to anyone. All such parties also agree that
Lender may modify this loan without the consent of or notice to anyone other
than the party with whom the modification is made.

PRIOR TO SIGNING THIS NOTE, BORROWER READ AND UNDERSTOOD ALL THE PROVISIONS OF
THIS NOTE, INCLUDING THE VARIABLE INTEREST RATE PROVISIONS. BORROWER AGREES TO
THE TERMS OF THE NOTE.

BORROWER:

BIOSOURCE TECHNOLOGIES, INC.

By: /s/ Robert L. Erwin                By: /s/ Michael D. Centron
    -----------------------------      -----------------------------------------
    ROBERT L. ERWIN, PRESIDENT         MICHAEL D. CENTRON, TREASURER
================================================================================
<PAGE>   73
                         CORPORATE RESOLUTION TO BORROW

<TABLE>
<CAPTION>
---------------------------------------------------------------------------------------------------------------
    PRINCIPAL       LOAN DATE       MATURITY      LOAN NO     CALL    COLLATERAL   ACCOUNT    OFFICER  INITIALS
<S>                 <C>             <C>          <C>          <C>     <C>          <C>        <C>
   $95,000.00       06-18-1998      06-18-1999   3400069792     10                  111721      274
---------------------------------------------------------------------------------------------------------------
References in the shaded area are for Lender's use only and do not limit the
applicability of this document to any particular loan or item.
---------------------------------------------------------------------------------------------------------------
</TABLE>

<TABLE>
<S>                                                  <C>         <C>
BORROWER: BIOSOURCE TECHNOLOGIES,                    (TIN:       LENDER:  SIERRAWEST BANK
          77-0154648                                                      CENTRAL PACIFIC REGION
          3333 VACA VALLEY PARKWAY, SUITE #1000                           1100 TEXAS ST.
          VACAVILLE, CA 95688-9421                                        FAIRFIELD, CA 94533
</TABLE>

================================================================================

I, THE UNDERSIGNED SECRETARY OR ASSISTANT SECRETARY OF BIOSOURCE TECHNOLOGIES,
INC. (THE "CORPORATION"), HEREBY CERTIFY THAT the Corporation is organized and
existing under and by virtue of the laws of the State of California as a
corporation for profit, with its principal office at 3333 VACA VALLEY PARKWAY,
SUITE 1000, VACAVILLE, CA 95688-9412, and is duly authorized to transact
business in the State of California.

I FURTHER CERTIFY that at a meeting of the Directors of the Corporation, duly
called and held on (resolutions attached hereto), at which a quorum was present
and voting, or by other duly authorized corporate action in lieu of a meeting,
the resolutions attached hereto were adopted, and that any two (2) of the
following named officers, employees, or agents of this Corporation, whose actual
signatures are shown below:

<TABLE>
<CAPTION>
        NAMES                  POSITIONS                   ACTUAL SIGNATURES
<S>                        <C>                             <C>
Robert L. Erwin            Chief Executive Officer         Robert L. Erwin
Michael D. Centron         Treasurer                       Michael D. Centron
</TABLE>

IN TESTIMONY WHEREOF, I have hereunto set my hand on June 18, 1998 and attest
that the signatures set opposite the names listed above are their genuine
signatures.

                                       CERTIFIED TO AND ATTESTED BY:

                                       By  John S. Rakitan
                                           -------------------------------------
                                           John S. Rakitan, Secretary

                                       By:
                                          --------------------------------------
                                          Authorized Signer

NOTE: In case the Secretary or other certifying officer is designated by the
foregoing resolutions as one of the signing officers, it is advisable to have
this certificate signed by a second Officer or Director of the Corporation.
================================================================================

<PAGE>   74
                            CHANGE IN TERMS AGREEMENT

<TABLE>
<CAPTION>
------------------------------------------------------------------------------------------------------------------------
     PRINCIPAL       LOAN DATE       MATURITY        LOAN NO       CALL    COLLATERAL     ACCOUNT     OFFICER   INITIALS
<S>                  <C>            <C>            <C>             <C>     <C>            <C>         <C>       <C>
    $95,000.00                      06-18-2000     3400069792       10                     111721       274
------------------------------------------------------------------------------------------------------------------------
References in the shaded area are for Lender's use only and do not limit the
applicability of this document to any particular loan or item.
------------------------------------------------------------------------------------------------------------------------
</TABLE>

<TABLE>
<S>                                                <C>        <C>
BORROWER: BIOSOURCE TECHNOLOGIES, INC.             (TIN:      LENDER:  SIERRAWEST BANK
          77-0154648                                                   CENTRAL PACIFIC REGION
          3333 VACA VALLEY PARKWAY, SUITE #1000                        1100 TEXAS ST.
          VACAVILLE, CA 95688-9421                                     FAIRFIELD, CA 94533
</TABLE>

PRINCIPAL AMOUNT: $95,000.00                   DATE OF AGREEMENT: JUNE 14, 1999

DESCRIPTION OF EXISTING INDEBTEDNESS. A PROMISSORY NOTE IN THE AMOUNT OF
$95,000-00.

DESCRIPTION OF COLLATERAL. UNSECURED.

DESCRIPTION OF CHANGE IN TERMS. THE MATURITY DATE HAS BEEN EXTENDED TO
06/18/2000. ALL OTHER TERMS AND CONDITIONS ARE TO REMAIN THE SAME.

PROMISE TO PAY. BIOSOURCE TECHNOLOGIES, INC. ("BORROWER") PROMISES TO PAY TO
SIERRAWEST BANK ("LENDER"), OR ORDER, IN LAWFUL MONEY OF THE UNITED STATES OF
AMERICA, THE PRINCIPAL AMOUNT OF NINETY FIVE THOUSAND & 00/100 DOLLARS
($95,000.00) OR SO MUCH AS MAY BE OUTSTANDING, TOGETHER WITH INTEREST ON THE
UNPAID OUTSTANDING PRINCIPAL BALANCE OF EACH ADVANCE. INTEREST SHALL BE
CALCULATED FROM THE DATE OF EACH ADVANCE UNTIL REPAYMENT OF EACH ADVANCE.

PAYMENT. BORROWER WILL PAY THIS LOAN IN ONE PAYMENT OF ALL OUTSTANDING PRINCIPAL
PLUS ALL ACCRUED UNPAID INTEREST ON JUNE. 18, 2000. IN ADDITION, BORROWER WILL
PAY REGULAR MONTHLY PAYMENTS OF ACCRUED UNPAID INTEREST BEGINNING JULY 18, 1999,
AND ALL SUBSEQUENT INTEREST PAYMENTS ARE DUE ON THE SAME DAY OF EACH MONTH AFTER
THAT. The annual interest rate for this Agreement is computed on a 365/360
basis; that is, by applying the ratio of the annual interest rate over a year of
360 days, multiplied by the outstanding principal balance, multiplied by the
actual number of days the principal balance is outstanding. Borrower will pay
Lender at Lender's address shown above or at such other place as Lender may
designate in writing. Unless otherwise agreed or required by applicable law,
payments will be applied first to accrued unpaid interest, then to principal,
and any remaining amount to any unpaid collection costs and late charges.

VARIABLE INTEREST RATE. The interest rate on this Agreement is subject to change
from time to time based on changes in an independent index which is the Prime
rate as published in the western edition of the Wall Street Journal (the
"Index"). The Index is not necessarily the lowest rate charged by Lender on its
loans. If the Index becomes unavailable during the term of this loan, Lender may
designate a substitute index after notice to Borrower. Lender will tell Borrower
the current Index rate upon Borrower's request. Borrower understands that Lender
may make loans based on other rates as well. The interest rate change will not
occur more often than each DAY. THE INDEX CURRENTLY IS 7.750%. THE INTEREST RATE
TO BE APPLIED TO THE UNPAID PRINCIPAL BALANCE OF THIS AGREEMENT WILL BE AT A
RATE OF 1.000 PERCENTAGE POINT OVER THE INDEX, RESULTING IN AN INITIAL RATE OF
8.750%. NOTICE: Under no circumstances will the interest rate on this Agreement
be more than the maximum rate allowed by applicable law.

PREPAYMENT. Borrower may pay without penalty all or a portion of the amount owed
earlier than it is due. Early payments will not, unless agreed to by Lender in
writing, relieve Borrower of Borrower's obligation to continue to make, payments
of accrued unpaid interest. Rather, they will reduce the principal balance due.

LATE CHARGE. If a payment is 10 DAYS OR MORE LATE, Borrower will be charged
5.000% OF THE REGULARLY SCHEDULED PAYMENT OR $15.00, WHICHEVER IS GREATER.

DEFAULT. Borrower will be in default if any of the following happens: (a)
Borrower fails to make any payment when due. (b) Borrower breaks any promise
Borrower has made to Lender, or Borrower fails to comply with or to perform when
due any other term, obligation, covenant, or condition contained in this
Agreement or any agreement related to this Agreement, or in any other agreement
or loan Borrower has with Lender. (c) Borrower defaults under any loan,
extension of credit, security agreement, purchase or sales agreement, or any
other agreement, in favor of any other creditor or person that may materially
affect any of Borrower's property or Borrower's ability to repay this Note or
perform Borrower's obligations under this Note or any of the Related Documents.
(d) Any representation or statement made or furnished to Lender by Borrower or
on Borrower's behalf is false or misleading in any material respect either now
or at the time made or furnished. (e) Borrower becomes insolvent, a receiver is
appointed for any part of Borrower's property, Borrower makes an assignment for
the benefit of creditors, or any proceeding is commenced either by Borrower or
against Borrower under any bankruptcy or insolvency laws. (f) Any creditor tries
to take any of Borrower's property on or in which Lender has a lien or security
interest. This includes a garnishment of any of Borrower's accounts with Lender.
(g) Any guarantor dies or any of the other events described in this default
section occurs with respect to any guarantor of this Agreement. (h) A material
adverse change occurs in Borrower's financial condition, or Lender believes the
prospect of payment or performance of the Indebtedness is impaired. (i) Lender
in good faith deems itself insecure.

If any default, other than a default in payment, is curable and if Borrower has
not been given a notice of a breach of the same provision of this Agreement
within the preceding twelve (12) months, it may be cured (and no event of
default will have occurred) if Borrower, after receiving written notice from
Lender demanding cure of such default: (a) cures the default within fifteen (15)
days; or (b) if the cure requires more than fifteen (15) days,. immediately
initiates steps which Lender deems in Lender's sole discretion to be sufficient
to cure the default and thereafter continues and completes all reasonable and
necessary steps sufficient to produce compliance as soon as reasonably
practical.

LENDER'S RIGHTS. Upon default, Lender may declare the entire unpaid principal
balance on this Agreement and all accrued unpaid interest immediately due,
without notice, and then Borrower will pay that amount. Upon Borrower's failure
to pay all amounts declared due pursuant to this section, including failure to
pay upon final maturity, Lender, at its option, may also, if permitted under
applicable law, increase the variable interest rate on this Agreement to 6.000
percentage points over the Index. Lender may hire or pay someone else to help
collect this Agreement if Borrower does not pay. Borrower also will pay Lender
that amount. This includes, subject to any limits under applicable law, Lender's
attorneys' fees and Lender's legal expenses whether or not there is a lawsuit,
including attorneys' fees and legal expenses for bankruptcy proceedings
(including efforts to modify or vacate any automatic stay or injunction),
appeals, and any anticipated post-judgment collection services. Borrower also
will pay any court costs, in addition to all other sums provided by law. THIS
AGREEMENT HAS BEEN DELIVERED TO LENDER AND ACCEPTED BY LENDER IN THE STATE OF
CALIFORNIA. IF

<PAGE>   75
06-18-1998                 CHANGE IN TERMS AGREEMENT
LOAN NO 3400069792               (CONTINUED)                              PAGE 2
================================================================================

THERE IS A LAWSUIT, BORROWER AGREES UPON LENDER'S REQUEST TO SUBMIT TO THE
JURISDICTION OF THE COURTS OF NEVADA COUNTY, THE STATE OF CALIFORNIA. THIS
AGREEMENT SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE
STATE OF CALIFORNIA.

RIGHT OF SETOFF. Borrower grants to Lender a contractual security interest in,
and hereby assigns, conveys, delivers, pledges, and transfers to Lender all
Borrower's right, title and interest in and to, Borrower's accounts with Lender
(whether checking, savings, or some other account), including without limitation
all accounts held jointly with someone else and all accounts Borrower may open
in the future, excluding however all IRA and Keogh accounts, and all trust
accounts for which the grant of a security interest would be prohibited by law.
Borrower authorizes Lender, to the, extent permitted by applicable law, to
charge or setoff all sums owing on this Agreement against any and all such
accounts.

LINE OF CREDIT. This Agreement evidences a revolving line of credit. Advances
under this Agreement, as well as directions for payment from Borrower's
accounts, may be requested orally or in writing by Borrower or by an authorized
person. Lender may, but need not, require that all oral requests be confirmed in
writing. Borrower agrees to be liable for all sums either: (a) advanced in
accordance with the instructions of an authorized person or (b) credited to any
of Borrower's accounts with Lender. The unpaid principal balance owing on this
Agreement at any time may be evidenced by endorsements on this Agreement or by
Lender's internal records, including daily computer print-outs. Lender will have
no obligation to advance funds under this Agreement if: (a) Borrower or any
guarantor is in default under the terms of this Agreement or any agreement that
Borrower or any guarantor has with Lender, including any agreement made in
connection with the signing of this Agreement; (b) Borrower or any guarantor
ceases doing business or is insolvent; (c) any guarantor seeks, claims or
otherwise attempts to limit, modify or revoke such guarantor's guarantee of this
Agreement or any other loan with Lender; (d) Borrower has applied funds provided
pursuant to this Agreement for purposes other than those authorized by Lender;
or (e) Lender in good faith deems itself insecure under this Agreement or any
other agreement between Lender and Borrower.

CONTINUING VALIDITY. Except as expressly changed by this Agreement, the terms of
the original obligation or obligations, including all agreements evidenced or
securing the obligation(s), remain unchanged and in full force and effect.
Consent by Lender to this Agreement does not waive Lender's right to strict
performance of the obligation(s) as changed, nor obligate Lender to make any
future change in terms. Nothing in this Agreement will constitute a satisfaction
of the obligation(s). It is the intention of Lender to retain as liable parties
all makers and endorsers of the original obligation(s), including accommodation
parties, unless a party is expressly released by Lender in writing. Any maker or
endorser, including accommodation makers, will not be released by virtue of this
Agreement. If any person who signed the original obligation does not sign this
Agreement below, then all persons signing below acknowledge that this Agreement
is given conditionally, based on the representation to Lender that the
non-signing party consents to the changes and provisions of this Agreement or
otherwise will not be released by it. This waiver applies not only to any
initial extension, modification or release, but also to all such subsequent
actions.

MISCELLANEOUS PROVISIONS. Lender may delay or forgo enforcing any of its rights
or remedies under this Agreement without losing them. Borrower and any other
person who signs, guarantees or endorses this Agreement, to the extent allowed
by law, waive any applicable statute of limitations, presentment, demand for
payment, protest and notice of dishonor. Upon any change in the terms of this
Agreement, and unless otherwise expressly stated in writing, no party who signs
this Agreement, whether as maker, guarantor, accommodation maker or endorser,
shall be released from liability. All such parties agree that Lender may renew
or extend (repeatedly and for any length of time) this loan, or release any
party or guarantor or collateral; or impair, fail to realize upon or perfect
Lender's security interest in the collateral; and take any other action deemed
necessary by Lender without the consent of or notice to anyone. All such parties
also agree that Lender may modify this loan without the consent of or notice to
anyone other than the party with whom the modification is made.

PRIOR TO SIGNING THIS AGREEMENT, BORROWER READ AND UNDERSTOOD ALL THE PROVISIONS
OF THIS AGREEMENT, INCLUDING THE VARIABLE INTEREST RATE PROVISIONS. BORROWER
AGREES TO THE TERMS OF THE AGREEMENT AND ACKNOWLEDGES RECEIPT OF A COMPLETED
COPY OF THE AGREEMENT.

BORROWER:

BIOSOURCE TECHNOLOGIES, INC.

By: /s/ Robert L. Erwin                   By: /s/ Michael D. Centron
    ---------------------------------         ----------------------------------
    ROBERT L. ERWIN, PRESIDENT                MICHAEL D. CENTRON, TREASURER
================================================================================

<PAGE>   76

                     DISBURSEMENT REQUEST AND AUTHORIZATION

<TABLE>
<CAPTION>
---------------------------------------------------------------------------------------------------------------------
    PRINCIPAL       LOAN DATE       MATURITY      LOAN NO       CALL    COLLATERAL    ACCOUNT     OFFICER    INITIALS
<S>                 <C>           <C>            <C>            <C>     <C>           <C>         <C>        <C>
   $95,000.00                     06-18-2000     3400069792      10                   111721        274
---------------------------------------------------------------------------------------------------------------------
References in the shaded area are for Lender's use only and do not limit the
applicability of this document to any particular loan or item.
---------------------------------------------------------------------------------------------------------------------
</TABLE>

<TABLE>
<S>                                              <C>        <C>
BORROWER: BIOSOURCE TECHNOLOGIES, INC.           (TIN:      LENDER: SIERRAWEST BANK
          77-0154648                                                CENTRAL PACIFIC REGION
          3333 VACA VALLEY PARKWAY, SUITE #1000                     1100 TEXAS ST.
          VACAVILLE, CA 95688-9421                                  FAIRFIELD, CA 94533
</TABLE>

================================================================================

LOAN TYPE. This is a Variable Rate (1.000% over Prime rate as published in the
western edition of the Wall Street Journal, making an initial rate of 8.750%),
Revolving Line of Credit Loan to a Corporation for $95,000.00 due on June 18,
2000.

PRIMARY PURPOSE OF LOAN. The primary purpose of this loan is for:

   [ ]         Personal, Family, or Household Purposes or Personal Investment.

   [X]         Business (Including Real Estate Investment).

SPECIFIC PURPOSE. The specific purpose of this loan is: BUSINESS LETTER OF
CREDIT.

DISBURSEMENT INSTRUCTIONS. Borrower understands that no loan proceeds will be
disbursed until all of Lender's conditions for making the loan have been
satisfied. Please disburse the loan proceeds of $95,000.00 as follows:

<TABLE>
<S>                                                            <C>
               Undisbursed Funds:                              $ 95,000.00
               Amount paid to others on Borrower's                   $0.00
               behalf:
                                                               -----------
               Note Principal:                                 $640,895.40
</TABLE>

FINANCIAL CONDITION. BY SIGNING THIS AUTHORIZATION, BORROWER REPRESENTS AND
WARRANTS TO LENDER THAT THE INFORMATION PROVIDED ABOVE IS TRUE AND CORRECT AND
THAT THERE HAS BEEN NO MATERIAL ADVERSE CHANGE IN BORROWER'S FINANCIAL CONDITION
AS DISCLOSED IN BORROWER'S MOST RECENT FINANCIAL STATEMENT TO LENDER. THIS
AUTHORIZATION IS DATED JUNE 14,1999.

BORROWER:

BIOSOURCE TECHNOLOGIES, INC.

By: /s/ Robert L. Erwin                    By: /s/ Michael D. Centron
    --------------------------------           ---------------------------------
    ROBERT L. ERWIN, PRESIDENT                 MICHAEL D. CENTRON, TREASURER
================================================================================

<PAGE>   77
                         CORPORATE RESOLUTION TO BORROW

<TABLE>
<CAPTION>
----------------------------------------------------------------------------------------------------------------------
    PRINCIPAL         LOAN DATE        MATURITY       LOAN NO        CALL    COLLATERAL    ACCOUNT    OFFICER  INITIALS
<S>                   <C>             <C>            <C>             <C>     <C>           <C>        <C>      <C>
   $95,000.00                         06-18-2000     3400069792       10                    111721      274
----------------------------------------------------------------------------------------------------------------------
References in the shaded area are for Lender's use only and do not limit the
applicability of this document to any particular loan or item.
----------------------------------------------------------------------------------------------------------------------
</TABLE>

<TABLE>
<S>                                              <C>       <C>
BORROWER: BIOSOURCE TECHNOLOGIES, INC.           (TIN:     LENDER: SIERRAWEST BANK
          77-0154648                                               CENTRAL PACIFIC REGION
          3333 VACA VALLEY PARKWAY, SUITE #1000                    1100 TEXAS ST.
          VACAVILLE, CA 95688-9421                                 FAIRFIELD, CA 94533
</TABLE>

I, THE UNDERSIGNED SECRETARY OR ASSISTANT SECRETARY OF BIOSOURCE TECHNOLOGIES,
INC. (THE "CORPORATION"), HEREBY CERTIFY THAT the Corporation is organized and
existing under and by virtue of the laws of the State of California as a
corporation for profit, with its principal office at 3333 VACA VALLEY PARKWAY,
STE 1000, VACAVILLE, CA 95688, and is duly authorized to transact business in
the State of California.

I FURTHER CERTIFY that at a meeting of the Directors of the Corporation, duly
called and held on October 16 , 1998, at which a quorum was present and voting,
or by other duly authorized corporate action in lieu of a meeting, the following
resolutions were adopted:

BE IT RESOLVED, that ANY TWO (2) of the following named officers, employees, or
agents of this Corporation, whose actual signatures are shown below:

<TABLE>
<CAPTION>
       NAMES                      POSITIONS                    ACTUAL SIGNATURES
       -----                      ---------                    -----------------
<S>                          <C>                               <C>
Robert L. Erwin              Chairman of the Board             Robert L. Erwin
Michael D. Centron           Treasurer                         Michael D. Centron
John S. Rakitan              Secretary
</TABLE>

acting for and on behalf of the Corporation and as its act and deed be, and they
hereby are, authorized and empowered:

    BORROW MONEY. To borrow from time to time from SierraWest Bank ("Lender"),
    on such terms s may be agreed upon between the Corporation and Lender, such
    sum or sums of money as in their judgment should be borrowed; however, not
    exceeding at any one time the principal amount of NINETY FIVE THOUSAND &
    00/100 DOLLARS ($95,000.00), in addition to such sum or sums of money as may
    be currently borrowed by the Corporation from Lender.

    EXECUTE NOTES. To execute and deliver to Lender the promissory note or
    notes, or other evidence of credit accommodations and/or revision agreement
    or other evidence of obligation of the Corporation, on Lender's forms, at
    such rates of interest and on such terms as may be agreed upon, evidencing
    the sums of money so borrowed or any indebtedness of the Corporation to
    Lender, and also to execute and deliver to Lender one or more renewals,
    extensions, modifications, refinancings, consolidations, or substitutions
    for one or more of the notes, any portion of the notes, or any other
    evidence of credit accommodations.

    GRANT SECURITY. To mortgage, pledge, transfer, endorse, hypothecate, or
    otherwise encumber and deliver to Lender, as security for the payment of any
    loans or credit accommodations so obtained, any promissory notes so executed
    (including any amendments to or modifications, renewals, and extensions of
    such promissory notes), or any other or further indebtedness of the
    Corporation to Lender at any time owing, however the same may be evidenced,
    any property now or hereafter belonging to the Corporation or in which the
    Corporation now or hereafter may have an interest, including without
    limitation all real property and all personal property (tangible or
    intangible) of the Corporation. Such property may be mortgaged, pledged,
    transferred, endorsed, hypothecated, or encumbered at the time such loans
    are obtained or such indebtedness is incurred, or at any other time or
    times, and may be either in addition to or in lieu of any property
    theretofore mortgaged, pledged, transferred, endorsed, hypothecated, or
    encumbered.

    EXECUTE SECURITY DOCUMENTS. To execute and deliver to Lender the forms of
    mortgage, deed of trust, pledge agreement, hypothecation agreement, and
    other security agreements and financing statements which may be required by
    Lender, and which shall evidence the terms and conditions under and pursuant
    to which such liens and encumbrances, or any of them, are given; and also to
    execute and deliver to Lender any other written instruments, any chattel
    paper, or any other collateral, of any kind or nature, which Lender may deem
    necessary or proper in connection with or pertaining to the giving of the
    liens and encumbrances. Notwithstanding the foregoing, any one of the above
    authorized persons may execute, deliver, or record financing statements.

    NEGOTIATE ITEMS. To draw, endorse, and discount with Lender all drafts,
    trade acceptances, promissory notes, or other evidences of indebtedness
    payable to or belonging to the Corporation in which the Corporation may have
    an interest, and either to receive cash for the same or to cause such
    proceeds to be credited to the account of the Corporation with Lender, or to
    cause such other disposition of the proceeds derived therefrom as they may
    deem advisable.

    FURTHER ACTS. In the case of lines of credit, to designate additional or
    alternate individuals as being authorized to request advances thereunder,
    and in all cases, to do and perform such other acts and things, to pay any
    and all fees and costs, and to execute and deliver such other documents and
    agreements as they may in their discretion deem reasonably necessary or
    proper in order to carry into effect the provisions of these Resolutions.

BE IT FURTHER RESOLVED, that any and all acts authorized pursuant to these
Resolutions and performed prior to the passage of these Resolutions are hereby
ratified and approved, that these Resolutions shall remain in full force and
effect and Lender may rely on these Resolutions until written notice of their
revocation shall have been delivered to and received by Lender. Any such notice
shall not affect any of the Corporation's agreements or commitments in effect at
the time notice is given.

BE IT FURTHER RESOLVED, that the Corporation will notify Lender in writing at
Lender's address shown above (or such other addresses as Lender may designate
from time to time) prior to any (a) change in the name of the Corporation, (b)
change in the assumed business name(s) of the Corporation, (c) change in the
management of the Corporation,, (d) change in the authorized signer(s), (e)
conversion of the Corporation to a new or different type of business entity, or
(f) change in any other aspect of the Corporation that directly or indirectly
relates to any agreements between the Corporation and Lender. No change in the
name of the Corporation will take effect until after Lender has been notified.
<PAGE>   78
09-01-1999                CORPORATE RESOLUTION TO BORROW
LOAN NO 3400369949                  (CONTINUED)                           PAGE 2
================================================================================

I FURTHER CERTIFY that the officers, employees, and agents named above are duly
elected, appointed, or employed by or for the Corporation, as the case may be,
and occupy the positions set opposite their respective names; that the foregoing
Resolutions now stand of record on the books of the Corporation; and that the
Resolutions are in full force and effect and have not been modified or revoked
in any manner whatsoever. The Corporation has no corporate seal, and therefore,
no seal is affixed to this certificate.

IN TESTIMONY WHEREOF, I have hereunto set my hand on June 14, 1999 and attest
that the signatures set opposite the names listed above are their genuine
signatures.

                                       CERTIFIED TO AND ATTESTED BY:

                                       By  John S. Rakitan
                                           -------------------------------------
                                           John S. Rakitan, Secretary

                                       By:
                                          --------------------------------------
                                          Authorized Signer

NOTE: In case the Secretary or other certifying officer is designated by the
foregoing resolutions as one of the signing officers, it is advisable to have
this certificate signed by a second Officer or Director of the Corporation.
================================================================================

<PAGE>   79
<TABLE>
<CAPTION>
-------------------------------------------------------------------------------------------------------------------
    PRINCIPAL       LOAN DATE        MATURITY       LOAN NO       CALL   COLLATERAL    ACCOUNT    OFFICER  INITIALS
<S>                 <C>             <C>            <C>            <C>    <C>           <C>        <C>      <C>
   $95,000.00       06-18-1998      06-18-1999     3400069792      10                   111721      274
-------------------------------------------------------------------------------------------------------------------
References in the shaded area are for Lender's use only and do not limit the
applicability of this document to any particular loan or item.
-------------------------------------------------------------------------------------------------------------------
</TABLE>

<TABLE>
<S>                                            <C>      <C>
BORROWER:  BIOSOURCE TECHNOLOGIES, INC.        (TIN:    LENDER:  SIERRAWEST BANK
           77-0154648)                                           CENTRAL PACIFIC REGION
           3333 VACA VALLEY PARKWAY, SUITE 1000                  1100 TEXAS ST
           VACAVILLE, CA 95688-9412                              FAIRFIELD, CA 94533
</TABLE>

================================================================================

LOAN TYPE. This is a Variable Rate (1.000% over Prime rate as published in the
western edition of the Wall Street Journal, making an initial rate of 9.500%),
Non-Revolving Line of Credit Loan to a Corporation for $95,000.00 due on June
18, 1999.

PRIMARY PURPOSE OF LOAN. The primary purpose of this loan is for:

        [ ]    Personal, Family, or Household Purposes or Personal Investment.

        [X]    Business (Including Real Estate Investment).

SPECIFIC PURPOSE. The specific purpose of this loan is: BUSINESS NON-REVOLVING
LETTER OF CREDIT.

DISBURSEMENT INSTRUCTIONS. Borrower understands that no loan proceeds will be
disbursed until all of Lender's conditions for making the loan have been
satisfied. Please disburse the loan proceeds of $95,000.00 as follows:

                  Undisbursed Funds                      $95,000.00
                                                         ----------
                  Note Principal:                        $95,000.00

FINANCIAL CONDITION. BY SIGNING THIS AUTHORIZATION, BORROWER REPRESENTS AND
WARRANTS TO LENDER THAT THE INFORMATION PROVIDED ABOVE IS TRUE AND CORRECT AND
THAT THERE HAS BEEN NO MATERIAL ADVERSE CHANGE IN BORROWER'S FINANCIAL CONDITION
AS DISCLOSED IN BORROWER'S MOST RECENT FINANCIAL STATEMENT TO LENDER. THIS
AUTHORIZATION IS DATED JUNE 18, 1998.

BORROWER:

BIOSOURCE TECHNOLOGIES, INC.

By: /s/ Robert L. Erwin                       By: /s/ Michael D. Centron
    -----------------------------------           ------------------------------
    ROBERT L. ERWIN, PRESIDENT                    MICHAEL D. CENTRON, TREASURER
================================================================================

<PAGE>   80
                                  CERTIFICATION

I, the undersigned, do hereby certify that I am the duly elected, acting and
qualified Secretary of Biosource Technologies, Inc., and that the foregoing
Resolutions were duly adopted by the Board of Directors of Biosource
Technologies, Inc., on September 12, 1995:

        WHEREAS, this Board of Directors' deems it to be in the best interest of
        the Company to maintain commercial banking relationships for the
        purposes of managing the funds of this Corporation.

        RESOLVED, that any two individuals holding the positions of Chief
        Executive Officer, President, Chief Financial Officer or Treasurer of
        this organization acting jointly are authorized and empowered to act for
        and on behalf of the Corporation to establish and maintain commercial
        banking relationships with Bank of America, Continental Pacific Bank and
        South Valley Bank or other federal or state chartered bank institution
        (hereinafter individually, generically referred to as the "Bank").

        FURTHER RESOLVED, that any two (2) individuals, each of whom holds at
        least one (1) of the following positions in the Company: Chief Executive
        Officer, President, Chief Financial Officer or Treasurer, acting
        jointly, are authorized to open checking accounts, interest bearing
        accounts, debit card accounts, credit card accounts, loans or lines of
        credit aggregating up to $1 million ($ 1,000,000), safe deposit boxes
        and other accounts required for day to day operations of the Company
        with a Bank. Transactions authorized under these accounts shall include
        checking payment transactions, wire transfers, Automated Clearing House
        (ACH) transactions, collection transactions, cash concentration
        transactions, foreign currency exchanges, depository transactions and
        other typical banking transactions for payment of the Company's
        obligations and collection of amounts owed to the Company.

        FURTHER RESOLVED, that any two individuals holding the positions of
        Chief Executive Officer, President, Chief Financial Officer or Treasurer
        of this Company, acting jointly, are authorized to appoint and terminate
        any Bank, add and remove employees of the Company authorized to withdraw
        funds and execute transactions and documents on behalf of the Company
        and update a Bank's signature cards.

        FURTHER RESOLVED, that any two individuals, each of whom is properly
        appointed in accordance with these resolutions, listed as signatories on
        behalf of the Company, are authorized to endorse, on behalf of the
        Company, any checks or other items payable to the organization or its
        order, to deposit such checks and other items into the account with or
        without such endorsement, and to direct withdrawals from the account by
        check drawn on the account or other-wise with a Bank.

        FURTHER RESOLVED, the Controller shall install such controls and
        procedures over cash, any Bank and accounting records as deemed
        necessary including but not limited to dual signatures controls,
        password controls over computer systems and segregation of duties. The
        Controller shall review all documents and agreements with any Bank to
        ensure appropriate controls.

<PAGE>   81
        FURTHER RESOLVED, that the Chief Executive Officer, President, Chief
        Financial Officer or Treasurer execute any and all documents including
        account agreements as are necessary and appropriate to institute,
        maintain and properly administer all banking services and to effectuate
        the foregoing resolutions.

IN WITNESS WHEREOF, I have executed this Certification this 8th day of November
1995.

                                       /s/  John S. Rakitan
                                       -----------------------------------------
                                       John S. Rakitan, Secretary

<PAGE>   82
                           LETTER OF CREDIT AGREEMENT
                              DATED: JUNE 18, 1998

in consideration of the issuance by SierraWest BANK ("you") of the irrevocable
letter of credit (the "Credit") contemplated in the attached Letter of Credit
Application ("Application 11) we, the applicant for the credit, hereby agree:

1. We agree to pay you, in U.S. Dollars, the amount of each sight draft which
you have honored or will honor purporting to be drawn under the Credit. our
payment shall reach you on or, at your request, in advance of the date you or a
confirming bank are to honor the draft; but in no case later than JUNE 18, 1999.
we also agree to pay to you the fees indicated on the Application and interest
at an aggregate annual interest rate which is 1.0% in excess of prime rate
quoted by the Wall Street Journal, Western Edition, in its Money Rates Table on
any amounts owing to you hereunder if not paid to you as and when they become
due. (If a range of prime rates is quoted in the Money Rates Table, the highest
of those rates will apply. Changes to the prime rate will result in a change in
the interest rate as of the publication date of the Wall Street Journal
containing the new prime rate quotation.) It is understood that your acceptance
of this agreement to pay you interest on the amount we owe shall not deprive you
of your right to insist upon immediate payment of all amounts we owe you in the
case of an event of default as recited in Paragraph 4 below. We authorize you to
charge the account noted on our Application or any other account or accounts any
of us maintains with you for each amount we owe you hereunder.

2. We understand that if you approve our Application and issue the Credit, the
Credit may be drawn upon by the Beneficiary regardless of any representations or
agreements the Beneficiary may have made to us to the contrary. In this respect,
we understand, that you will be unconditionally obligated to, and will, timely
honor a properly presented draft drawn by the Beneficiary under the Credit. If
there is a drawing, we will repay you as provided in Paragraph 1 even if we
dispute the right of the Beneficiary to have drawn upon the credit.

3. Our obligations to you under this agreement are secured by each and every
item of personal property (and the proceeds thereof) covered by any security
agreement we or any of us has or in the future will have executed in your favor
pursuant to the terms and conditions of the security agreement covering that
collateral whether or not the security agreement specifically refers to this
agreement. However, personal property collateral taken in connection with
"consumer credit, 11 as that term is contemplated by the Federal Truth- In-
Lending Act, will not serve as collateral for our obligations hereunder unless
those of us who have executed the security agreement covering such collateral
specifically agree to the contrary. Any real property which serves as security
under a deed of trust in your favor will also serve as collateral hereunder if
the deed of trust or another writing signed by the trustor under the deed of
trust so states. We will furnish you with additional security of a value and
character satisfactory to you if you demand that we so do.

4. If (a) we fail to keep a satisfactory margin of security with you at all
times; (b) any of us make an assignment for the benefit of creditors; (c) any
voluntary or involuntary petition in bankruptcy is filed by or against us; (d)
any receiver of any of our property is appointed; or (e) any act of bankruptcy
or state of insolvency occurs as to any of us, at your option all of our
obligations to you under this agreement shall become immediately due and payable
without demand or notice notwithstanding any credit or time allowed to us under
any instrument further evidencing our obligations or otherwise. Without limited
the foregoing, if you so demand we will deposit with you the full amount of the
Credit whether or not the Credit has been drawn upon. This deposit shall be
maintained by you until the Credit expires unless before such expiration
drawings occur and are not otherwise covered by us, in which case you are
authorized to apply from the deposit the amounts necessary to cover such
drawings towards satisfaction of our obligations hereunder. If a deposit is
required and maintained, you shall have a security interest therein. You shall
have no obligation to pay interest to us. If we fail to make a deposit within
(S) days of your demand, you are authorized to foreclose upon any and all of the
collateral for our obligations under this agreement as provided in the security
agreement or deed of trust, if any, covering the respective properties, and as
provided by law. if not necessary to cover previous drawing under the Credit or
our obligations to you which have already matured, the proceeds of all
collateral disposition(s) shall be credited to the deposit described in this
paragraph. When all of our potential obligations to you under this agreement
have become known, quantified and satisfied, any amount remaining in the deposit
shall be paid to us, it being agreed that a payment to any of us shall be deemed
to be made to all of us and that we will settle among ourselves which of us is
or are ultimately to receive the amount so paid.

5. We have reviewed and approve of the proposed form of the Credit. If there are
any amendments or modifications of the terms of the Credit, this agreement shall
be binding upon us with regard to the Credit as amended.

6. The users of the Credit shall be deemed our agents and we assume all risks of
their acts or omissions. Neither you nor your correspondents shall be
responsible for (a) the adequacy or validity of any insurance or insurer; (b)
the validity, sufficiency or genuineness of documents, even if they are
ultimately proven to be in any or all respects invalid, insufficient, fraudulent
or forged; (c) the solvency or responsibility of any party issuing any
documents; (d) delay in arrival or failure to arrive of any documents; (e) delay
in giving or failure to give notice of arrival or any other notice; (f) failure
of any draft to bear adequate reference to the Credit; (g) failure of documents
to accompany any draft at negotiation or failure of any person to endorse on the
Credit the amount of any draft or to surrender or take up the Credit or to send
documents apart from drafts as required by the terms of the Credit, each of
which provisions, if contained in the Credit itself, it is agreed may be waived
by you; or (h) errors, omissions, interruptions or delays in transmission or
delivery of any message by mail, cable, telegraph, wireless or otherwise,
whether or not they may be in cipher. You shall not be responsible for any
error, neglect, or default of any of your correspondents and none of the above
shall affect,

<PAGE>   83
impair, or prevent the vesting of any of your rights or powers under this
agreement. without limiting these specific provisions, we further agree that any
action taken in good faith by you or by any of your correspondents in connection
with the Credit shall be binding on us and shall not put you or your
correspondent under any resulting liability to us. We make like agreement as to
any other inaction or omission on your part or that of your correspondents,
unless committed by you in breach of good faith.

7. To be effective, any waiver by you of any of your rights under this agreement
must be written and signed by you or your authorized agent. Unless expressly
stated therein, any waiver of your rights shall apply only to transactions or
breaches which occur prior to the date of the waiver and shall not apply to any
continuance of a breach after the waiver.

8. If our request for the Credit is made in connection with an investment we are
making, we acknowledge that you have not made nor will you make, any
investigation or representations of or concerning this investment, nor any of
the sales agents or promoters of the investment, its qualification or exemption
from qualification under any federal or state securities law, or any other
matter relating to this investment. Our obligations to you in connection with
the Credit are totally independent of the investment. We will repay any sums
that we may owe you if the Beneficiary draws on the Credit whether or not we
have a right to rescind our investment or receive any return whatsoever on the
investment.

9. If the Application is signed by one individual the terms (we, 11 "our" and
"us" shall be read throughout as III," "my" or I'm,," as the case may be. If
signed by two or more parties, our obligations to you shall be joint and
several.

Applicant: BIOSOURCE TECHNOLOGIES, INC.

By:  /s/ Robert L. Erwin
     ----------------------------------
     ROBERT L. ERWIN, PRESIDENT

By:: /s/ Robert L. Erwin
     ----------------------------------
     MICHAEL D. CENTRON, TREASURER

<PAGE>   84
                          LETTER OF CREDIT APPLICATION

                               Date: JUNE 18, 1998

TO:     SierraWest Bank
        1100 Texas St
        Fairfield, CA 94533

Please issue your Irrevocable Letter of Credit for the benefit of BIOSOURCE
TECHNOLOGIES, INC. in favor of GREEN RIVER AREA DEVELOPMENT as the Beneficiary,
whose address is 3860 US HIGHWAY 60 WEST, OWENSBORO, KENTUCKY 42301 for the
account of the undersigned applicant up to the aggregate sum of NINETY FIVE
THOUSAND DOLLARS AND NO/100 $95,000.00 available by draft or drafts drawn in the
United States dollars on you at sight when accompanied by:

        A statement certifying that bonds or undertakings established on behalf
        of BIOSOURCE TECHNOLOGIES, INC. are outstanding and proceeds of the
        draft are to be retained and used by you to meet any payments of loss,
        cost, or expense which you might thereafter be required to make under
        such bonds or undertakings.

This Letter of Credit is to expire at your office at 1:00 P.M. Pacific Time of
JUNE 18, 1999. Special instructions:

I. The following documents must be in possession of Sierra West Bank prior to
any payments to Green River Area Development District:

        1. A letter from the Executive Director of Green River Area Development
        District certifying that Biosource Technologies, Inc. is in default on
        its loan from Green River Area Development District in a specified
        amount. The term "Default" means Biosource Technologies, Inc. is past
        due on loan payments owed to Green River Development District by a
        minimum of forty five (45) days without being cured.

        2. A sight draft properly completed and executed by the Executive
        Director of Green River Area Development District in the amount
        specified as being in default in the letter from said Executive
        Director, as set forth above in item 1 under this paragraph I.

II. Green River Area Development District may not assign its rights and/or
obligations under this Standby Letter of Credit.

You are authorized to debit drawings and fees from account no. N/A _ or to our
other accounts as agreed in the attached Irrevocable Letter of Credit Agreement.
We understand that your fees for this transaction include:

<PAGE>   85
  N/A   payable upon issuance

We, and each of us, agree to the above terms and conditions and to those on the
Irrevocable Letter of Credit Agreement and we acknowledge that we have received
a completed copy of this Application and reviewed and understand the, terms of
the Irrevocable Letter of Credit Agreement.

Applicant:  BIOSOURCE TECHNOLOGIES, INC.

        BY:  /s/  Robert L. Erwin
             -------------------------------
             ROBERT L. ERWIN, PRESIDENT

        BY:  /s/  Michael D. Centron
             -------------------------------
             MICHAEL D. CENTRON, TREASURER<PAGE>   1

                               SECOND AMENDMENT TO
                              AMENDED AND RESTATED
                           REVOLVING CREDIT AGREEMENT

        This SECOND AMENDMENT TO AMENDED AND RESTATED REVOLVING CREDIT AGREEMENT
(this "Second Amendment") is made as of July 27, 2000 (the "Effective Date"), by
and among ADVANCED FIBRE COMMUNICATIONS, INC., a Delaware corporation (with its
successors and permitted assigns, the "Borrower"), the LENDERS from time to time
parties hereto (including their Assignees), BNP PARIBAS (formerly known as
Banque Nationale de Paris), a French banking association, as arranger and
administrative agent (the "Administrative Agent"), and BANK OF AMERICA, N.A.
(formerly known as Bank of America National Trust and Savings Association), a
national banking association, as syndication agent (the "Syndication Agent").

        WHEREAS, the Borrower, the Lenders, the Administrative Agent and the
Syndication Agent are parties to that certain AMENDED AND RESTATED REVOLVING
CREDIT AGREEMENT, dated as of July 29, 1999 (as amended, modified or otherwise
supplemented prior to the date hereof, the "Agreement");

        WHEREAS, the Borrower has requested a 364-day extension of the
Termination Date pursuant to Section 2.1(b) of the Agreement; and

        WHEREAS, the Lenders have unanimously agreed to extend the Termination
Date subject to the amendments, terms and conditions hereinafter set forth;

        NOW, THEREFORE, in consideration of the premises and mutual covenants
herein contained, the parties hereby agree as follows:

        SECTION 1. DEFINED TERMS. Capitalized terms that are used in this Second
Amendment without definition shall have the same meanings herein as in the
Agreement.

        SECTION 2. TERMINATION DATE. The definition of the term "Termination
Date" in Exhibit A to the Agreement is hereby amended to delete the phrase,
"July 27, 2000" and to substitute therefor the phrase "July 26, 2001."

        SECTION 3. CHANGE IN AGGREGATE REVOLVING CREDIT COMMITMENT. Effective
from and after July 27, 2000, the Aggregate Revolving Credit Commitment
(representing the amount available for borrowing under the Agreement, subject to
the terms and conditions of the Agreement) shall be reduced from $30,000,000 to
$25,000,000; and the definition of "Aggregate Revolving Credit Commitment"
contained in Exhibit A to the Agreement shall be changed

                                      -1-
<PAGE>   2

accordingly. Also effective from and after July 27, 2000, the Revolving Credit
Commitment for each of BNP Paribas and Bank of America N.A. shall be reduced
from $15,000,000 to $12,500,000. There shall be no reduction in the amount of
the L/C Commitment, which shall continue to be $10,000,000. The preceding
reductions are subject to the condition that as of the close of business (New
York time) on July 26, 2000, the aggregate Available Revolving Credit Commitment
(after reduction for any then pending requests for Loans or for issuance of
Letters of Credit) shall be not less than $5,000,000.

        SECTION 4. AMENDMENT TO SUBSECTION 7.1(a). Subsection 7.1(a) of the
Agreement shall be amended to read in its entirety as follows (and shall apply
to the fiscal quarter ending on or about September 30, 2000 and each fiscal
quarter thereafter):

               (a)    MINIMUM QUICK RATIO. Permit the Quick Ratio on the last
                      day of any fiscal quarter of the Borrower to be less than
                      2.0 to 1.0.

        SECTION 5. AMENDMENT TO SUBSECTION 7.1(d). Subsection 7.1(d) of the
Agreement shall be amended to read in its entirety as follows (and shall apply
retroactively to the fiscal quarters immediately preceding and including the
fiscal quarter ending on or about September 30, 2000 and each fiscal quarter
thereafter):

               (d)    PROFITABILITY TEST. Permit (i) operating losses in any one
                      fiscal quarter to exceed $10,000,000, (ii) operating
                      losses in any two consecutive fiscal quarters to exceed
                      $15,000,000 in the aggregate, or (iii) operating losses in
                      any three consecutive quarters (regardless of the
                      magnitude of such losses); provided, however, that for
                      purposes of this covenant (x) non-cash, nonrecurring
                      charges taken by the Borrower or its Subsidiaries for the
                      purchase of in-process technology, and (y) non-cash,
                      nonrecurring charges taken against investments made by the
                      Borrower or its Subsidiaries relating to activities of the
                      Borrower's current material foreign subsidiary (with
                      respect to its assets) up to the amount of $7,000,000 in
                      the aggregate, shall not be considered in any calculation
                      of operating losses.

        SECTION 6. FEES AND EXPENSES. On or before the Effective Date, the
Borrower shall pay (a) to the Administrative Agent the administrative agency fee
and (b) to each of the Lenders the extension fee, in each case as provided in
that certain letter from the Administrative Agent to the Borrower dated July 6,
2000. Promptly upon demand, the Borrower shall reimburse the Administrative
Agent for all reasonable expenses, including expenses of counsel, incurred by
the Administrative Agent, the Syndication Agent and the Lenders in connection
with this Second Amendment.

        SECTION 7. REPRESENTATIONS AND WARRANTIES. The Borrower hereby
represents to the Lenders, the Administrative Agent and the Syndication Agent
that:

               (a)    REPRESENTATIONS AND WARRANTIES. Its representations and
        warranties contained in Article VIII to the Agreement are true and
        correct as of

                                      -2-
<PAGE>   3

        the date hereof (unless stated to relate solely to an earlier date, in
        which case such representations and warranties are true and correct as
        of such earlier date).

               (b)    ENFORCEABILITY. The execution and delivery by this Second
        Amendment, and the performance of its obligations under this Second
        Amendment and the Agreement, as amended hereby, are within its corporate
        powers and have been duly authorized by all necessary corporate action
        on its part. This Second Amendment and the Agreement, as amended hereby,
        are its valid and legally binding obligations, enforceable in accordance
        with their terms, except as enforceability may be limited by bankruptcy,
        insolvency, reorganization or other similar laws affecting the
        enforcement of creditors' rights generally and by general principles of
        equity, regardless of whether such enforceability is considered in a
        proceeding in equity or at law.

               (c)    NO DEFAULT. No Default or Event of Default has occurred
        and is continuing.

        SECTION 8. EFFECT OF AMENDMENT. Except as expressly amended and modified
by this Second Amendment, all provisions of the Agreement shall remain in full
force and effect. After this Second Amendment becomes effective, all references
in the Agreement (or in any other Credit Document) to "this Agreement",
"hereof", "herein" or words of similar effect referring to the Agreement shall
be deemed to be references to the Agreement as amended by this Second Amendment.
This Second Amendment shall not be deemed to expressly or impliedly waive, amend
or supplement any provision of the Agreement other than as set forth herein.

        SECTION 9. EFFECTIVENESS. This Second Amendment shall become effective
as of the date hereof upon receipt by the Administrative Agent of (a)
counterparts of this Second Amendment (whether by facsimile or otherwise)
executed by each of the other parties hereto and (b) the fees and expenses set
forth in Section 6 herein.

        SECTION 10. GOVERNING LAW. This Second Amendment shall be governed by,
and construed in accordance with, the internal laws of the State of California
without regard to any otherwise applicable principles of conflicts of law.

        SECTION 11. COUNTERPARTS. This Second Amendment may be executed in any
number of counterparts and by different parties on separate counterparts, and
each counterpart shall be deemed to be an original, and all such counterparts
shall together constitute but one and the same instrument.

        SECTION 12. SECTION HEADINGS. The various headings and sub-headings of
this Second Amendment are inserted for convenience only and shall not affect the
meaning or interpretation of this Second Amendment or the Agreement or any
provision hereof or thereof.

                                      -3-
<PAGE>   4

        IN WITNESS WHEREOF, the parties hereto have caused this Second Amendment
to be duly executed and delivered by their proper and duly authorized officers
as of the day and year first above written.

Advanced Fibre Communications, Inc.,        Bank of America, N.A.,
as Borrower                                 as Lender and Syndication Agent

        /s/  Keith E. Pratt                       /s/  Douglas Meckelnburg
--------------------------------------      ------------------------------------
By:    Keith E. Pratt                       By:    Douglas Meckelnburg
Title: Vice President & CFO                 Title: Vice President

BNP Paribas,
as Lender and Administrative Agent

        /s/  Jennifer Y. Cho
--------------------------------------
By:     Jennifer Y. Cho
Title:  Vice President

        /s/  Stephanie Reyes
--------------------------------------
By:    Stephanie Reyes
Title: Assistant Vice President

                                      -4-

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