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                         VARIABLE RATE-INSTALLMENT NOTE

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AMOUNT                            NOTE DATE                       MATURITY DATE                   TAX IDENTIFICATION #
<S>                               <C>                             <C>                             <C>
$1,673,800.00                     September 7, 2000               April 14, 2004                  77-0187280
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For Value Received, the undersigned promise(s) to pay to the order of Comerica
Bank-California ("Bank"), at any office of the Bank in the State of California
One Million Six Hundred Thousand Seventy Three Eight Hundred and no/100 Dollars
(U.S.) in installments of $ 26,315.79 * each plus interest on the unpaid balance
from the date of this Note at a per annum rate equal to the Bank's base rate
from time to time in effect plus 0.500 % per annum until maturity, whether by
acceleration or otherwise, or until Default, as later defined, and after that at
a default rate equal to the rate of interest otherwise prevailing under this
Note plus 3% per annum (but in no event in excess of the maximum rate permitted
by law). Interest shall be calculated for the actual number of days the
principal is outstanding on the basis of a 360-day year if this Note evidences a
business or commercial loan or a 365-day year if a consumer loan. The Bank's
"base rate" is that annual rate of interest so designated by the Bank and which
is charged by the Bank from time to time. Interest rate changes will be
effective for interest computation purposes as and when the Bank's base rate
changes. Installments of principal and accrued interest due under this Note
shall be payable on the 14th day of each month , commencing October 14, 2000 ,
and the entire remaining unpaid balance of principal and accrued interest shall
be payable on the Maturity Date set forth above. If the frequency of principal
and interest installments is not otherwise specified, installments of principal
and interest due under this Note shall be payable monthly on the first day of
each month.

In the event the periodic installments set forth above are inclusive of
interest, these installments are calculated at an assumed fixed interest rate
and an assumed amortization term. The amortization term ends on April 14, 2004 .
In the event this Note evidences a business or commercial loan and the Bank's
base rate changes, the Bank, at its sole option, may from time to time
recalculate the periodic installment amount so that the remaining periodic
installments will fully amortize the remaining loan balance within the remaining
amortization term in equal installments at the interest rate then being charged
under this Note. THE UNDERSIGNED AGREE(S) TO PAY THE PERIODIC INSTALLMENTS AS
THEY MAY BE RECALCULATED BY THE BANK, AT THE BANK'S SOLE OTPION, FROM TIME TO
TIME AND ACKNOWLEDGE(S) THAT A RECALCULATION SHALL NOT AFFECT THE MATURITY DATE
OR THE OTHER TERMS AND PROVISIONS OF THIS NOTE. If this Note or any installment
under this Note shall become payable on a day other than a day on which the Bank
is open for business, this payment may be extended to the next succeeding
business day and interest shall be payable at the rate specified in this Note
during this extension. Any payments of principal in excess of the installment
payments required under this Note need not be accepted by the Bank (except as
required under applicable law), but if accepted shall apply to the installments
last falling due. A late installment charge equal to 5% of each late installment
may be charged on any installment payment not received by the Bank within 10
calendar days after the installment due date, but acceptance of payment of this
charge shall not waive any default under this Note.

This Note and any other indebtedness and liabilities of any kind of the
undersigned (or any of them) to the Bank, and any and all modifications,
renewals or extensions of it, whether joint or several, contingent or absolute,
now existing or later arising, and however evidenced (collectively
"Indebtedness") are secured by and the Bank is granted a security interest in
all items deposited in any account of any of the undersigned with the Bank and
by all proceeds of these items (cash or otherwise), all account balances of any
of the undersigned from time to time with the Bank, by all property of any of
the undersigned from time to time in the possession of the Bank and by any other
collateral, rights and properties described in each and every deed of trust,
mortgage, security agreement, pledge, assignment and other agreement which has
been or will at any time(s) later be, executed by any (or all) of the
undersigned to or for the benefit of the Bank (collectively "Collateral").
Notwithstanding the above, (i) to the extent that any portion of the
Indebtedness is a consumer loan, that portion shall not be secured by any deed
of trust or mortgage on or other security interest in any of the undersigned's
principal dwelling or in any of the undersigned's real property which is not a
purchase money security interest as to that portion, unless expressly provided
to the contrary in another place, or (ii) if the


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undersigned (or any of them) has (have) given or give(s) Bank a deed of trust or
mortgage covering real property, that deed of trust or mortgage shall not secure
this Note or any other Indebtedness of the undersigned (or any of them), unless
expressly provided to the contrary in another place.

If the undersigned (or any of them) or any guarantor under a guaranty of all or
part of the Indebtedness ("guarantor") (a) fail(s) to pay this Note or any of
the Indebtedness when due, by maturity, acceleration or otherwise, or fail(s) to
pay any Indebtedness owing on a demand basis upon demand; or (b) fail(s) to
comply with any of the terms or provisions of any agreement between the
undersigned (or any of them) or any guarantor and the Bank; or (c) become(s)
insolvent or the subject of a voluntary or involuntary proceeding in bankruptcy,
or a reorganization, arrangement or creditor composition proceeding, (if a
business entity) ceases(s) doing business as a going concern, (if a natural
person) die(s) or become(s) incompetent, (if a partnership) dissolve(s) or any
general partner of it dies, become incompetent or becomes the subject of a
bankruptcy proceeding or (if a corporation or a limited liability company) is
the subject of a dissolution, merger or consolidation; or (d) if any warranty or
representation made by any of the undersigned or any guarantor in connection
with this Note or any of the Indebtedness shall be discovered to be untrue or
incomplete; or (3) if there is any termination, notice of termination, or breach
of any guaranty, pledge, collateral assignment or subordination agreement
relating to all or any part of the Indebtedness; or (f) if there is any failure
by any of the undersigned or any guarantor to pay when due any of its
indebtedness (other than to the Bank) or in the observance or performance of any
term, covenant or condition in any document evidencing, securing, or relating to
such Indebtedness; or (g) if the Bank deems itself insecure, believing that the
prospect of payment of this Note or any of the Indebtedness is impaired or shall
fear deterioration, removal or waste of any of the Collateral; or (h) if there
is filed or issued a levy or writ of attachment or garnishment or other like
judicial process upon the undersigned (or any of them) or any guarantor or any
of the Collateral, including without limit, any accounts of the undersigned (or
any of them) or any guarantor with the Bank, then the Bank, upon the occurrence
of any of these events (each a "Default"), may at its option and without prior
notice to the undersigned (or any of them), declare any or all of the
Indebtedness to be immediately due and payable (notwithstanding any provisions
contained in the evidence thereof to the contrary), sell or liquidate all or any
portion of the Collateral, set off against the Indebtedness any amounts owing by
the Bank to the undersigned (or any of them), charge interest at the default
rate provided in the document evidencing the relevant Indebtedness and exercise
any one or more of the rights and remedies granted to the Bank by any agreement
with the undersigned (or any of them), declare any or all of the Indebtedness to
be immediately due and payable (notwithstanding any provisions contained in the
evidence thereof to the contrary), sell or liquidate all or any portion of the
Collateral, set off against the Indebtedness any amounts owing by the Bank to
the undersigned (or any of them), charge interest at the default rate provided
in the document evidencing the relevant Indebtedness and exercise any one or
more of the rights and remedies granted to the Bank by an agreement with the
undersigned (or any of them) or given to it under applicable law. In addition,
if this Note is secured by a deed of trust or mortgage covering real property,
then the trustor or mortgagor shall not mortgage or pledge the mortgaged
premises as security for any other indebtedness or obligations. This Note,
together with all other Indebtedness secured by said deed of trust or mortgage,
shall become due and payable immediately, without notice, at the option of the
Bank, (a) if said trustor or mortgagor shall mortgage or pledge the mortgaged
premises for any other Indebtedness or obligations or shall convey, assign or
transfer the mortgaged premises by deed, installment sale contract or other
instrument, or (b) if the title to the mortgaged premises shall become vested in
any other person or party in any manner whatsoever, or (c) if there is any
disposition (through one or more transactions) of legal or beneficial title to a
controlling interest of said trustor or mortgagor. All payments under this Note
shall be in immediately available United States funds, without setoff or
counterclaim.

If this Note is signed by two or more parties (whether by all as makers or by
one or more as an accommodation party or otherwise), the obligations and
undertakings under this Note shall be that of all and any two or more jointly
and also of each severally. This Note shall bind the undersigned, and the
undersigned's respective heirs, personal representatives, successors and
assigns.

The undersigned waive(s) presentment, demand, protest, notice of dishonor,
notice of demand or intent to demand, notice of acceleration or intent to
accelerate, and all other notices and agree(s) that no extension or indulgence
to the undersigned (or any of them) or release,


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substitution or nonenforcement of any security, or release or substitution of
any of the undersigned, any guarantor or any other party, whether with or
without notice, shall affect the obligations of any of the undersigned. The
undersigned waive(s) all defenses or right to discharge available under Section
3-605 of the California Uniform Commercial Code and waive(s) all other
suretyship defenses or right to discharge. The undersigned agree(s) that the
Bank has the right to sell, assign, or grant participations, or any interest, in
any or all of the Indebtedness, and that, in connection with this right, but
without limiting its ability to make other disclosures to the full extent
allowable, the Bank may disclose all documents and information which the Bank
now or later has relating to the undersigned or the Indebtedness. The
undersigned agree(s) that the Bank may provide information relating to this Note
or to the undersigned to the Bank's parent, affiliation, subsidiaries and
service providers.

The undersigned agree(s) to reimburse the holder or owner of this Note for any
and all costs and expenses (including without limit, court costs, legal expenses
and reasonable attorney fees, whether inside or outside counsel is used, whether
or not suit is instituted and, if suit is instituted, whether at the trial court
level, appellate level, in a bankruptcy, probate or administrative proceeding or
otherwise incurred in collecting or attempting to collect this Note or incurred
in any other matter or proceeding relating to this Note.

The undersigned acknowledge(s) and agree(s) that there are no contrary
agreements, oral or written, establishing a term of this Note and agree(s) that
the terms and conditions of this Note may not be amended, waived or modified
except in a writing signed by an officer of the Bank expressly stating that the
writing constitutes an amendment, waiver or modification of the terms of this
Note. As used in this Note, the word "undersigned" means, individually and
collectively, each maker, accommodation party, endorser and other party signing
this Note in a similar capacity. If any provision of this Note in unenforceable
in whole or part for any reason, the remaining provisions shall continue to be
effective. THIS NOTE IS MADE IN THE STATE OF California AND SHALL BE GOVERNED BY
AND CONSTRUED IN ACCORDANCE WITH THE INTERNAL LAWS OF THE STATE OF California
WITHOUT REGARD TO CONFLICT OF LAWS PRINCIPLES.

The maximum interest rate shall not exceed the highest applicable usury ceiling.

THE UNDERSIGNED AND THE BANK ACKNOWLEDGE THAT THE RIGHT TO TRIAL BY JURY IS A
CONSTITUTIONAL ONE, BUT THAT IT MAY BE WAIVED. EACH PARTY, AFTER CONSULTING (OR
HAVING HAD THE OPPORTUNITY TO CONSULT) WITH COUNSEL OF THEIR CHOICE, KNOWINGLY
AND VOLUNTARILY, AND FOR THEIR MUTUAL BENEFIT, WAIVES ANY RIGHT TO TRIAL BY JURY
IN THE EVENT OF LITIGATION REGARDING THE PERFORMANCE OR ENFORCEMENT OF, OR IN
ANY WAY RELATED TO, THIS NOTE OR THE INDEBTEDNESS.

This Note is subject to the Loan & Security Agreement dated May 15, 2000 and any
and all subsequent renewals thereof.

     INITIAL HERE: /s/ DAL
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PharmChem, Inc.

By: /s/ David A. Lattanzio              Its: VP & CFO
    ---------------------------------------------------------
    SIGNATURE OF  David A. Lattanzio         TITLE  VP & CFO




1505-A O'Brien Drive        Menlo Park      CA           USA          94025
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STREET ADDRESS              CITY            STATE        COUNTRY      ZIP CODE


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