Document:

<PAGE>

                                                                   EXHIBIT 10.10

[CONFIDENTIAL TREATMENT REQUESTED. CONFIDENTIAL PORTIONS OF THIS AGREEMENT HAVE
BEEN REDACTED AND HAVE BEEN SEPARATELY FILED WITH THE COMMISSION]

                   ASSIGNMENT OF PATENT RIGHTS AND TECHNOLOGY

          This Assignment is entered into this 1st day of August, 1991, by and
between the Board of Regents of The University of Texas System, an agency of the
State of Texas (hereinafter "Assignor" which term includes successors and
assigns), Dr. Adam Heller, an individual residing at 5317 Valburn Circle,
Austin, Texas 78731 (hereinafter "Heller"), and E. Heller and Company, a Texas
Corporation, having its principal place of business at 5317 Valburn Circle,
Austin, Texas 78731 (hereinafter "Assignee," which term includes successors and
assigns).

                              W I T N E S S E T H:

          WHEREAS, by virtue of two assignments one of which was executed by
Heller and Brian A. Gregg (coinventor) on August 28, 1989, and the second of
which was executed by Heller and Ruben Maidan (coinventor) on March 22, 1991,
which are attached hereto as Exhibit "A", Assignor is the owner of all right,
title, and interest in and to certain Patent Rights (as hereinafter defined)
"Enzyme Electrodes" and "Interferant Eliminating Biosensors"; and

          WHEREAS, Assignor is the owner of all right, title, and interest in
and to certain Technology (as hereinafter defined) and Know-How (as hereinafter
defined) relating to "Enzyme Electrodes", "Interferant Eliminating Biosensors",
and "Preactivated Interferant Eliminating Biosensors"; and

          WHEREAS, under the Rules and Regulations promulgated by the Assignor,
Heller has a partial interest in *** of the royalties received by Assignor from
licensing or other disposition of the Patent Rights, the Technology, and the
Know-How, after costs of licensing and obtaining a patent or other protection
have first been recaptured by Assignor (hereinafter the "Heller Interest") and
Heller has assigned such interest to Assignee; and,

          WHEREAS, Heller desires to confirm the assignment of the Heller
Interest to Assignee; and,

          WHEREAS, Assignor and Heller entered into a letter agreement dated
August 1, 1991, attached hereto as Exhibit "B", and desire to confirm that
agreement; and,

          WHEREAS, Assignee desires to acquire all of Assignor's right, title,
and interest in, to, and under the Patent Rights, the Technology, and the
Know-How, and desires to confirm the assignment of the Heller Interest to
Assignee; and,

          WHEREAS, Assignor desires to assign, sell, and convey the entire
right, title, and interest of Assignor in the Patent Rights, the Technology, and
the Know-How to Assignee, its successors and assigns, in exchange for the
consideration hereinafter set forth; and,

          NOW, THEREFORE, in consideration of the covenants and agreements
herein contained and other good and valuable consideration, the sufficiency of
which is hereby acknowledged, the parties hereto agree as follows:

*** Confidential treatment requested
<PAGE>

                                   ARTICLE I

                                  DEFINITIONS

     1.1  Technology. The term "Technology" as used herein shall mean all
          ----------
inventions, patents, patent applications, and rights listed on Exhibits "C" and
"D".

     1.2  Patent Rights. The term "Patent Rights" as used herein shall mean all
          -------------
patent applications listed on Exhibit "C" or patents that issue thereon, and any
subject matter that may in the future be included in a continuation,
continuation-in-part, or divisional, to these patent applications, which is
disclosed in writing to Assignor and which names Heller as either sole or joint
inventor including an invention disclosure entitled "Preactivated Interferant
Eliminating Biosensors" attached hereto as Exhibit "D".

     1.3  Know-How. The term "Know-How" as used herein shall mean existing
          --------
technology not claimed in the Patent Rights, but nevertheless proprietary,
valuable trade secrets, inventions, processes, procedures, methods, product
codes, formulas, techniques, designs, drawings, technical and clinical data, and
other valuable and technical information relating to "Enzyme Electrodes",
"Interferant Eliminating Biosensors", and "Preactivated Interferant Eliminating
Biosensors".

     1.4  Licensed Products. The term "Licensed Products" as used herein shall
          -----------------
mean products covered by one or more claims of the Patent Rights or produced by
methods covered by one or more claims of such Patent Rights or utilizing or
incorporating Technology or Know-How.

     1.5  Licensed Processes. The term "Licensed Processes" as used herein shall
          ------------------
mean all methods and procedures covered by one or more claims of the Patent
Rights or utilizing or incorporating Technology or Know-How for the manufacture
or use of Licensed Products.

     1.6  Income. The term "Income" as used herein shall mean all income
          ------
received by Assignee from the sale, licensing, or other transfer of the Patent
Rights, the Technology, or the Know-How to third parties (excluding any
reimbursement to Assignee by a third party of the actual out-of-pocket legal
expenses and costs Assignee has incurred for filing, prosecution and maintenance
of any issued patent and/or patent application covered under Patent Rights,
documentation of which shall be provided in Assignee's semi-annual written
reports).

                                  ARTICLE II

                                  ASSIGNMENT

     2.1 Assignment by Assignor. Assignor hereby assigns, sells, and conveys to
         ----------------------
Assignee, its successors and assigns, the entire right, title, and interest
throughout the world in and to the Patent Rights and the Technology, subject
only to: (a) any rights of the United States Government which may exist now or
in the future due to a research funding agreement to which the United States
Government may be a party; and (b) the conditions of this Agreement.

                                      -2-
<PAGE>

     2.2  Assignment by Heller. Heller hereby confirms the assignment, sale, and
          --------------------
conveyance to Assignee, its successors and assigns, of the entire right, title,
and interest throughout the world in and to the Heller Interest.

                                  ARTICLE III

                                 CONSIDERATION

     3.1  License to Third Party. Assignor, Heller, and Assignee agree that, in
          ----------------------
the event the Patent Rights, the Technology, and/or the Know-How are sold,
licensed, or otherwise disposed of for value to a third party or parties,
Assignor shall receive *** derived from such sale, license, or other
disposition, subject to retention by Assignee of its *** or other consideration.
Accordingly, Assignee agrees to pay to Assignor *** received from a third party
or third parties beyond the *** or other consideration. In the event that
Assignee engages in litigation and/or settlement negotiations to protect Patent
Rights, *** by Assignee shall be paid to Assignor, provided, however, that
Assignee shall be entitled to deduct reasonable attorneys' fees and court costs
incurred in such litigation and/or settlement negotiations. Such payment to
Assignor shall be made within thirty (30) days following the expiration of the
calendar quarter in which Assignee receives a payment. All payments shall be
made to The University of Texas at Austin at: The University of Texas at Austin,
Office of the Executive Vice President and Provost, Main Building 201, Austin,
Texas 78712-1111, Attention: Patricia C. Ohlendorf.

     3.2  Manufacture and Sale of Licensed Products by Assignee. Should Assignee
          -----------------------------------------------------
elect to itself manufacture, sell, or otherwise dispose of for value Licensed
Products or Licensed Processes, Assignor and Assignee agree to negotiate the
compensation Assignee shall pay to Assignor. Assignee further agrees that the
compensation due Assignor shall be an amount representing the equivalent of what
Assignor reasonably believes it would have received as royalty, licensing fees,
and other compensation ("Compensation") had Assignor licensed or otherwise
disposed of for value the Technology, Patent Rights and Know How (hereafter
"Technology", for the purposes of this Paragraph 3.2) to a party other than
Assignee ("Third Party"). This equivalent amount shall be negotiated in good
faith by the parties, taking into account, but not limited to, the following:
(a) Compensation Assignee must pay to a Third Party for the use of comparable
Technology; (b) Compensation Assignee receives for its own license or other
disposal for value of the Technology to a Third Party; (c) The nature and scope
of the license or other disposal for value of the Technology by Assignor to a
Third Party, as exclusive or nonexclusive, restricted or nonrestricted in terms
of territory or with respect to whom the Licensed Products and/or Licensed
Processes may be sold; (d) Assignor's policies and procedures regarding the
licensing or other disposal for value of its intellectual property; (e) The
effect of the Technology in promoting the sales of other products of the Third
Party; (f) The duration of Technology related patents and term of any license;
(g) The established or projected profitability of the Licensed Products and
Licensed Processes; (h) The utility and advantages of the Licensed Products and
Licensed Processes over old modes or existing products or processes, if any,
that can be used for achieving similar results; (i) The portion of the profit or
the selling price of Licensed Products and Licensed Processes that may be
customary in the particular business or in comparable businesses which market
the Technology, if any, or similar Technology; (j) The portion of the profit
from the sale or other disposal for value of Licensed Products and Licensed
Processes that should be credited to the Technology as

*** Confidential treatment requested

                                      -3-
<PAGE>

distinguished from non-Technology related elements, such as business risks by
the Third Party and/or significant features or improvements to the Technology
added by the Third Party; and (k) The Compensation due Assignor had the
Technology been licensed pursuant to Paragraph 3.1. Any negotiating dispute
shall be subject to mediation as described in Article XI hereto. Payment by
Assignee to Assignor shall be made as described in Paragraph 3.1 above.

     3.3  Assignment Fee. Assignee shall pay to Assignor a fee of *** by
          --------------
September 1, 1991.

                                   ARTICLE IV

                           BOOKS, RECORDS, AND REPORTS

     4.1  Books. Assignee shall maintain true and complete books of account
          -----
containing an accurate record of all data necessary for the proper computation
of income, royalty and other payments, and the calculation thereof, as well as
attorneys' fees and court costs. Assignor or its authorized representative shall
have the right to examine such books, under appropriate terms of confidentiality
with Assignee, at all reasonable times, upon ten (10) days prior written notice
for the sole purpose of verifying the accuracy of reports rendered by Assignee.
Such examination shall be made during normal business hours at Assignee's
principal place of business or such other location as Assignor and Assignee may
agree.

     4.2  Payments and Reports. Assignee shall submit to Assignor semi-annual
          --------------------
written reports covering that fiscal period of Assignee and accurately
identifying income and expenses in sufficient form and detail as to enable
Assignor to determine the income, royalties, or other payments due. Such reports
shall be due thirty (30) days following each semi-annual period. A report shall
be submitted, even if no income has been received or no royalties or other
payments are due during the fiscal quarters of that period, in accord with the
terms of Paragraph 3.1 herein. Reports shall be mailed to The University of
Texas at Austin at the address in Paragraph 3.1 herein.

     4.3  Commercialization Report. Assignee shall submit to Assignor, at the
          ------------------------
address listed in paragraph 3.1 herein, a written report by September 1 of each
year which details Assignee's commercialization efforts during the preceding
year with regard to Patent Rights, Technology, and Know-How.

                                   ARTICLE V

                                CONFIDENTIALITY

     5.1  Duty of Confidence. Assignor and Assignee each agree that all
          ------------------
information contained in documents marked "confidential" which are forwarded to
one by the other shall be received in strict confidence, used only for the
purposes of this Agreement, and not disclosed by the recipient party (except as
required by law or court order), its agents or employees without the prior
written consent of the other party, unless such information (a) was in the
public domain at the time of disclosure, (b) later became part of the public
domain through no act or omission of the recipient party, its employees, agents,
successors or assigns, (c) was lawfully disclosed to the recipient party

*** Confidential treatment requested

                                      -4-
<PAGE>

by a third party having the right to disclose it, (d) was already known by the
recipient party at the time of disclosure, (e) was independently developed, (f)
is required to be submitted to a government agency pursuant to any preexisting
obligation, or (g) must be disclosed under the Texas Open Records Act.

     5.2  Degree of Care. Each party's obligation of confidentiality hereunder
          --------------
shall be fulfilled by using at least the same degree of care with the other
party's confidential information as it uses to protect its own confidential
information. This obligation shall exist while this Agreement is in force.

                                  ARTICLE VI

                       CONSIDERATION RECEIVED BY HELLER

     6.1  Sufficiency of Consideration. Heller acknowledges that he has received
          ----------------------------
sufficient consideration for assigning his rights in the Patent Rights, the
Technology, and the Know-How hereunder from Assignee and no further
consideration shall be received by Heller from either Assignor or Assignee in
connection with this Assignment. Heller expressly waives his right to receive
any royalties or other benefits under the Rules and Regulations of the Board of
Regents of The University of Texas System relating to intellectual property
rights in the Patent Rights, the Technology, and the Know-How and acknowledges
that any such royalties or other benefits that would be due to Heller but for
this Agreement shall be and remain the property of The University of Texas at
Austin. Specifically: (a) as stated in Exhibit B hereto, Subsection (1), the ***
paid to The University of Texas at Austin remaining after the deduction of an
amount covering patent expenses thus far paid by The University in regards to
Patent Rights, shall be shared with Heller's coinventors in the proportion each
would receive were Heller still included among the inventors who share in The
University's income; and (b) as stated in Exhibit B hereto, Subsection (7), the
*** of any income paid to The University of Texas at Austin under this
Assignment shall be shared with Heller's coinventors in the proportion each
would receive were Heller still included among the inventors who share in The
University's income.

                                  ARTICLE VII

                             RESERVATION BY ASSIGNOR

     7.1  Reservation. Assignee and Heller acknowledge and agree to the
          -----------
reservation by Assignor for all components of The University of Texas System of
a *** nonexclusive license to use Patent Rights, Technology, and Know-How in
educational and research activities.

                                 ARTICLE VIII

                                REPRESENTATIONS

     8.1  Representation. The parties hereto represent and warrant that they
          --------------
have the right and authority to enter into this Assignment and that they have
not executed or entered into any other agreements inconsistent with the terms
and provisions hereof.

*** Confidential treatment requested

                                      -5-
<PAGE>

     8.2  Documents. Heller and Assignor covenant that Heller, Assignor, and
          ---------
their heirs, legal representatives, assigns, administrators, and executors,
will, at the expense of Assignee, its successors and assigns, execute all papers
and perform such other acts as may be reasonably necessary to give Assignee, its
successors and assigns, the full benefit of this Assignment.

                                  ARTICLE IX

                            USE OF NAME OR FACILITIES

     9.1  Name. Assignee shall not use the name of Assignor or The University of
          ----
Texas at Austin in any promotional material.

     9.2  Facilities. Heller acknowledges and agrees that any direct
          ----------
commercialization efforts with respect to Patent Rights, Technology, or Know-How
are his or Assignee's private endeavor and shall not be carried out using
facilities or other resources of Assignor or The University of Texas at Austin.
Assignee shall not use the facilities or other resources of Assignor or The
University of Texas at Austin.

                                   ARTICLE X

                                    BREACH

     10.1 Default. In the event that Assignee shall default in any of its
          -------
material obligations under this Assignment (including but not limited to the
payment of compensation to Assignor), Assignor may require the reconveyance of
the assigned intellectual property should Assignor give Assignee written notice
of default, and such default is not cured within ninety (90) days of Assignee's
receipt of such notice. Assignee further agrees to notify Assignor of any such
cure in writing sent to the address listed in Paragraph 3.1 herein, and shall
describe such cure to Assignor's satisfaction. Assignor's right to require
reconveyance hereunder shall not preclude Assignor from seeking or obtaining any
other remedy to which it may be entitled, at any time.

                                  ARTICLE XI

                                   MEDIATION

     11.1 Dispute Resolution. Any dispute arising under or related to this
          ------------------
Assignment which involves a question of fact may be submitted by either party
for mediation, if the parties are unable to resolve the dispute within a
reasonable time after written notice is sent by one party to the other of the
existence of such dispute. The institution of any mediation proceeding shall not
relieve Assignee of its compensation obligations described in Article III
herein, during the pendency of such proceeding.

                                      -6-
<PAGE>

                                  ARTICLE XII

                                 GOVERNING LAW

     12.1 Construction and Enforcement. This Assignment shall be construed and
          ----------------------------
enforced in accordance with the laws of the United States of America and of the
State of Texas.

                                 ARTICLE XIII

                            DISCLAIMER OF WARRANTY

     13.1 Specific Disclaimer. Assignor makes no representations other than
          -------------------
those expressly stated in this Assignment, and specifically, Assignor MAKES NO
EXPRESS OR IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR
PURPOSE, OR THAT THE TECHNOLOGY OR PATENT RIGHTS OR KNOW HOW WILL NOT INFRINGE
ANY PATENT OR OTHER PROPRIETARY RIGHT.

                                  ARTICLE XIV

                                INDEMNIFICATION

     14.1 Hold Harmless. Assignee shall hold harmless and indemnify Assignor,
          -------------
the University of Texas System, and The University of Texas at Austin, its
officers, employees and agents from and against any claims, demands, or causes
of action whatsoever, including without limitation those arising on account of
any injury or death of persons or damage to property caused by, or arising out
of, or resulting from, the exercise or practice of the Assignment granted
hereunder by Assignee or its officers, employees, agents or representatives.

                                  ARTICLE XV

                                  DISPOSITION

     15.1 Assignee may not assign or otherwise dispose of (except by license)
the Patent Rights and Technology without the prior written consent of Assignor.

                                      -7-
<PAGE>

         EXECUTED by the duly authorized representatives of the parties on the
date indicated below the signatures of the parties hereto.

ASSIGNOR:                                          HELLER
--------                                           ------
BOARD OF REGENTS OF THE
UNIVERSITY OF TEXAS SYSTEM

By: /s/ Hans Mark                              By: /s/ Adam Heller
    ------------------------------------           -----------------------------
Hans Mark                                           Adam Heller
Chancellor

Date:  May 15, 1992                            Date: ILLEGIBLE
      ----------------------------------             ---------------------------

APPROVED AS TO CONTENT:                        ASSIGNEE:
                                               --------
                                               E. HELLER AND COMPANY

By: /s/ G. J. Fonken                           By: /s/ Ephraim Heller
    ------------------------------------           -----------------------------
G. J. Fonken                                   (Print) Ephraim Heller
                                                       -------------------------
Executive Vice President and Provost           Title Illegible
                                               ---------------------------------
The University of Texas at Austin

Date:                                          Date:  ILLEGIBLE
      ----------------------------------             ---------------------------

APPROVED AS TO FORM:

By: /s/ Dudley R. Dobie, Jr.
    ------------------------------------
Dudley R. Dobie, Jr.
Office of General Counsel

Date: 5/11/92
      ----------------------------------
<PAGE>

THE STATE OF TEXAS

COUNTY OF TRAVIS

          BEFORE ME, the undersigned Notary Public, on this day personally
appeared Hans Mark, Chancellor for The University of Texas System, an agency of
the State of Texas, known to me to be the person whose name is subscribed to the
foregoing instrument, and acknowledged to me that he executed the same for the
purposes and consideration therein expressed.

         GIVEN UNDER MY HAND AND SEAL OF OFFICE this 15th day of May.

                                 /s/ Becky F. Boyer
                                 -----------------------------------------------
                                 Notary Public, State of Texas

(SEAL)                           My Commission Expires: 9/19/92
                                                        ------------------------

                                 /s/ Becky F. Boyer
                                     -------------------------------------------
                                 Typed or Printed Name of Notary
<PAGE>

THE STATE OF TEXAS

COUNTY OF TRAVIS

          BEFORE ME, the undersigned Notary Public, on this day personally
appeared Adam Heller of 5317 Valburn Circle, Austin, Texas, known to me to be
the person whose name is subscribed to the foregoing instrument, and
acknowledged to me that he executed the same for the purposes and consideration
therein expressed.

          GIVEN UNDER MY HAND AND SEAL OF OFFICE this 17th day of April, 1992.

                                    /s/ Norma R. Horn
                                    --------------------------------------------
                                    Notary Public, State of Texas

(SEAL)                              My Commission Expires: 4/5/95
                                                           ---------------------

                                    /s/ Norma R. Horn
                                        ----------------------------------------
                                    Typed or Printed Name of Notary
<PAGE>

THE STATE OF TEXAS

COUNTY OF TRAVIS

         BEFORE ME, the undersigned Notary Public, on this day personally
appeared Ephraim Heller of E. Heller and Company, 5317 Valburn Circle, Austin,
Texas 78731, known to me to be the person whose name is subscribed to the
foregoing instrument, and acknowledged to me that he executed the same for the
purposes and consideration therein expressed.

         GIVEN UNDER MY HAND AND SEAL OF OFFICE this 17th day of April, 1992.

                                      /s/ Norma R. Horn
                                      ------------------------------------------
                                      Notary Public, State of Texas

(SEAL)                                My Commission Expires: 4/5/95
                                                             -------------------

                                      /s/ Norma R. Horn
                                      ------------------------------------------
                                      Typed or Printed Name of Notary
<PAGE>

                                    EXHIBIT A

                                                              FILE NO. UTSB: 413
                                                                          PATENT

                               A S S I G N M E N T
                               -------------------

         FOR GOOD AND VALUABLE CONSIDERATION, the receipt, sufficiency and
adequacy of which are hereby acknowledged, the undersigned, does hereby:

         SELL, ASSIGN AND TRANSFER to Board of Regents, The University of Texas
System (the "Assignee"), having a place of business at 201 West 7th Street,
Austin, Texas, 78701, the entire right, title and interest for the United States
and all foreign countries in and to any and all improvements which are disclosed
in the application for United States Letters Patent, Serial No. 389,226, which
                                                     ------------------
has been filed on August 2, 1989 and is entitled ENZYME ELECTRODES, such
                                                 ------ ----------
application and all divisional, continuing, substitute, renewal, reissue and all
other applications for patent which have been or shall be filed in the United
States and all foreign countries on any of such improvements; all original and
reissued patents which have been or shall be issued in the United States and all
foreign countries on such improvements; and specifically including the right to
file foreign applications under the provisions of any convention or treaty and
claim priority based on such application in the United States;

         AUTHORIZE AND REQUEST the issuing authority to issue any and all United
States and foreign patents granted on such improvements to the Assignee;

         WARRANT AND COVENANT that no assignment, grant, mortgage, license or
other agreement affecting the rights and property herein conveyed has been or
will be made to others by the undersigned, and that the full right to convey the
same as herein expressed is possessed by the undersigned;

         COVENANT, when requested and at the expense of the Assignee, to carry
out in good faith the intent and purpose of this assignment, the undersigned
will execute all divisional, continuing, substitute, renewal, reissue, and all
other patent applications on any and all such improvements; execute all rightful
oaths, declarations, assignments, powers of attorney and other papers;
communicate to the Assignee all facts known to the undersigned relating to such
improvements and the history thereof; and generally do everything possible which
the Assignee shall consider desirable for vesting title to such improvements in
the Assignee, and for securing, maintaining and enforcing proper patent
protection for such improvements;
<PAGE>

         TO BE BINDING on the heirs, assigns, representatives and successors of
the undersigned and extend to the successors, assigns and nominees of the
Assignee.

(Signature) /s/ Brian A. Gregg                Date August 28, 1989
            ---------------------------            -----------------------------
      Name: Brian A. Gregg

(Signature) /s/ Adam Heller                   Date August 28, 89
            ---------------------------            -----------------------------
      Name: Adam Heller

(Signature)                                   Date  Recorded Patent & Transfer
                                                    Office 9/28/89
            ___________________________            -----------------------------
      Name:

(Signature)                                   Date  /s/ ILLEGIBLE, Commissioner
                                                    of Patents
            ___________________________            -----------------------------
      Name:

STATE OF TEXAS                              )
                                            )     ss.
COUNTY OF TRAVIS                            )

         BEFORE ME, the undersigned authority, on this 28th day of August,
1989, personally appeared Brian A. Gregg and Adam Heller known to me to be the
persons whose names subscribed to the foregoing instrument and acknowledged to
me that they executed the same of their own free will for the purposes and
consideration therein expressed.

                                             /s/ Norma R. Horn
                                             -----------------------------------
                                             Notary or Consular Officer

[SEAL]

                             ARNOLD, WHITE & DURKEE

P. O. Box 4433                           2001 Jefferson Davis Highway, Suite 40,
Houston, Texas  77210                    Arlington, Virginia 22202

                                      -2-
<PAGE>

                               EXHIBIT A

                                                                       UTSB: 465
                                                                          PATENT

                              A S S I G N M E N T
                              - - - - - - - - - -

    FOR GOOD AND VALUABLE CONSIDERATION, the receipt, efficiency and adequacy
of which are hereby acknowledged, the undersigned, do hereby:
    SELL, ASSIGN AND TRANSFER to Board of Regents, The University of Texas
System (the "Assignee"), having a place of business at 201 West 7th Street,
Austin, Texas, 78701, the entire right, title and interest for the United States
and all foreign countries in and to any and all improvements which are disclosed
in the application for United States Letters Patent, Serial No. 07/664,054,
which has been filed on March 4, 1991, and is entitled INTERFERANT ELIMINATING
BIOSENSORS, such application and all divisional, continuing, substitute,
renewal, reissue and all other applications for patent which have been or shall
be filed in the United States and all foreign countries on any of such
improvements; all original and reissued patents which have been or shall be
issued in the United States and all foreign countries on such improvements; and
specifically including the right to file foreign applications under the
provisions of any convention or treaty and claim priority based on such
application in the United States;
    AUTHORIZE AND REQUEST the issuing authority to issue any and all United
States and foreign patents granted on such improvements to the Assignee;
    WARRANT AND COVENANT that no assignment, grant, mortgage, license or other
agreement affecting the rights and property herein conveyed has been or will be
made to others by the undersigned, and that the full right to convey the same as
herein expressed is possessed by the undersigned;
    COVENANT, when requested and at the expense of the Assignee, to carry out in
good faith the intent and purpose of this assignment, the undersigned will
execute all divisional, continuing, substitute, renewal, reissue, and all other
patent applications on any and all such improvements; execute all rightful
oaths, declarations, assignments, powers of attorney and other papers;
communicate to the Assignee all facts known to the undersigned relating to such
improvements and the history thereof; and generally do everything possible which
the Assignee shall consider desirable for vesting title to such improvements in
the Assignee, and for securing, maintaining an enforcing proper patent
protection for such improvements;
    TO BE BINDING on the heirs, assigns, representatives and successors of the
undersigned and extend to the successors, assigns and nominees of the Assignee.

(Signature)  /s/ Adam Heller                 Date  March 22, 1991
           ________________________________       ____________________________
      Name:      Adam Heller

(Signature)  /s/ Ruben Maidan                Date  March 22, 1991
           ________________________________       ____________________________
      Name:      Ruben Maidan

STATE OF TEXAS     )
                   ) ss.
COUNTY OF TRAVIS   )
          _________

    BEFORE ME, the undersigned authority, on this 22nd day of March, 1991,
personally appeared ADAM HELLER and RUBEN MAIDAN, known to me to be the persons
whose names are subscribed to the foregoing instrument and acknowledged to me
that they executed the same of their own free will for the purposes and
consideration therein expressed.

                                              /s/ Constance J. Hannan
                                              ________________________________
                                              Notary of Consular Officer
                                              Constance J. Hannan
                                              My commission expires 4/11/93

[SEAL]

                            ARNOLD, WHITE & DURKEE

  P.O. Box 4433                         2001 Jefferson Davis Hwy., Ste. 401
  Houston, Texas  77210                 Arlington, Virginia  22202
<PAGE>

                                   EXHIBIT B

August 1, 1991

Dr. Adam Heller
Department of Chemical Engineering
CPE 4.450

Re:      UTSB:413 - "Enzyme Electrodes"
         UTSB:465 - "Interferant Eliminating Biosensors"

Dear Dr. Heller:

         I write to followup our previous communications regarding your request
that The University exclusively license or release to you the inventions
entitled UTSB:413 and UTSB:465, which you co-invented. I am setting out below
conditions under which The University will release and/or assign to you, as
appropriate, its intellectual property rights in the subject matter presently
described in patent applications UTSB:413 and UTSB:465, and any subject matter
that may in the future be included in a continuation, continuation-in-part, or
divisional, to these patent applications. These conditions are consistent with
similar arrangements into which The University has entered:

         (1)      You (or your company) will pay The University a nonrefundable
                  fee of *** by September 1, 1991. These funds shall be used by
                  The University to pay patent expenses that we have thus far
                  incurred on these cases. In the unlikely event that funds
                  remain after deduction of those expenses, we shall share with
                  your coinventors the proportion of the *** inventors' share
                  that each would receive were you still included among the
                  inventors who share in The University's income;

         (2)      Effective August 1, 1991, you (or your company) shall assume
                  all financial and decision making responsibility for
                  maintenance and prosecution of these patent applications and
                  any patents that issue, including foreign counterparts. The
                  University shall inform Arnold, White & Durkee of this shift
                  in responsibility. Should you wish to have the cases
                  transferred from Arnold, White & Durkee to your own attorney,
                  The University will cooperate in this transfer subject to
                  reimbursement of any associated expenses above ***;

         (3)      You (and your company) agree to, and acknowledge, reservation
                  by The University of Texas System for itself and its component
                  institutions of a royalty-free, nonexclusive license to use
                  the inventions in educational and research activities;

         (4)      Any direct commercialization efforts regarding these
                  inventions will be your (or your company's) private endeavor
                  and cannot be carried out using University facilities or other
                  resources;

         (5)      In the event the inventions are commercialized, *** of any
                  royalties or other income that you (or your company) receive
                  from such commercialization shall be paid to The University as
                  royalty after the total gross income received by you (or your
                  company) reaches ***;

*** Confidential treatment requested
<PAGE>

Dr. Adam Heller
August 1, 1991
Page 2

         (6)      You will inform this office in writing by September 1st of
                  each year of any commercialization efforts made regarding the
                  inventions during the previous year. At the time any royalty
                  payments shall become due to The University, they shall be
                  paid on a quarterly basis; and

         (7)      You acknowledge that you shall not receive any portion of the
                  inventors' share of income which The University may receive
                  from commercialization of these inventions. Your coinventors
                  will receive from The University the proportion of the
                  inventors' share that they would have received were you still
                  going to receive a portion of such funds.

         It is our intent to include in this release/assignment the disclosure
that you recently made of an invention entitled "Preactivated Interferant
Eliminating Biosensors." However, any future inventions, other than those that
can be filed as continuations or continuations-in-part on the existing
applications, cannot be included in this release/assignment. All such future
inventions are subject to individual disclosure and review in accordance with
our usual procedures. At such time we will give fair consideration to any
request by you that an invention be released to you.

         After careful consideration, I have decided that these terms are
considered final by The University. If you agree to them, please sign in the
space indicated below on both copies and return one to me. We shall then
consider the terms effective and operational although formal assignment
documents for the two pending patent applications will need to be prepared and
executed. We will ask The University of Texas System to prepare these documents
upon receipt of an executed copy of this letter.

                                                Sincerely yours,

                                                /s/ G.J. Fonken
                                                G.J. Fonken
GJF:cm

cc:      Associate Vice President Patricia C. Ohlendorf
         Dean Herbert H. Woodson
         Associate Dean Dale E. Klein
         Professor Thomas Edgar
         Mr. Dudley R. Dobie, Jr.
         Ms. Paulette Braeutigam
         Dr. Brian A. Gregg
         Dr. Ruben Maiden

/s/ Adam Heller
----------------------------------------------
Dr. Adam Heller

Date August 4, 1991
     -----------------------------------------

                                      -2-

<PAGE>

                                   EXHIBIT C

                 U.S. Serial
                 Filing No.
UT File No.        (Date)           Title                     Inventor(s)
-----------      -----------        -----                     -----------

UTSB:413           389,226          Enzyme Electrodes         Brian A. Gregg
                   (3-2-89)                                   Adam Heller

UTSB:465           664,054          Interferant Eliminating
                                       Biosensors             Adam Heller
                   (3-4-91)                                   Ruben Maidan

<PAGE>

                                    EXHIBIT D

                              INVENTION DISCLOSURE
                        The University of Texas at Austin

                                 I. Descriptive

1. Title of invention ***.
                      ---
2. Brief description. Is the Invention a new process, composition of matter, a
   device, or one or more products? A new use for or an improvement to an
   existing product or process?

***
---

Use additional sheets to elaborate or attach descriptive materials.

3. From the description, pick out and expand on novel and unusual features. How
   does the invention differ from present technology? What problems does it
   solve or what advantages does it possess?

***
---

*** Confidential treatment requested
<PAGE>

                                      ***

                                      -2-

*** Confidential treatment requested
<PAGE>

4.   If not indicated previously, what are possible uses for the invention? In
     addition to immediate applications, are there other uses that might be
     realized in the future?

***
--------------------------------------------------------------------------------
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________

5.   Does the invention possess disadvantages or limitations? Can they be
     overcome? How?

________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________

6.   Enclose sketches, drawings, photographs, and other materials that help
     illustrate the description. (Rough artwork, flow sheets, Polaroid
     photographs, and penciled graphs are satisfactory as long as they tell a
     clear and understandable story. Enclosed.

                           II.  Other Pertinent Data

1.   Are there publications--theses, reports, preprints, reprints, etc.--
     pertaining to the invention? Please list with publication dates, and attach
     copies insofar as possible. Include manuscripts for publication (submitted
     or not), news releases, feature articles, and items from internal
     publications.

     a.   ***
          ----------------------------------------------------------------------
     b.
          ______________________________________________________________________
     c.
          ______________________________________________________________________
     d.
          ______________________________________________________________________

2.   Are laboratory records and data available? Give reference numbers and
     physical location, but do not enclose.
                               ---

***
--------------------------------------------------------------------------------
________________________________________________________________________________

3.   Are related patents or other publications known to the inventor? Please
     list.

***
-------------------------------------------------------------------------------
_______________________________________________________________________________
_______________________________________________________________________________

                                      -3-

*** Confidential treatment requested
<PAGE>

4.   Date, place, and circumstances of first public disclosure.

***
-------------------------------------------------------------------------------
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________

5.   Was the work that led to the invention sponsored? If yes, attach copy of
     contact or agreement if possible, and fill in the appropriate blanks below.

     a.   Title of government agency         ***             Conract No.
                                    ---------------------                   ____
     b.   Name of industrial company
                                    ____________________________________________
     c.   Name of university sponsor
                                    ____________________________________________
     d.   Other sponsor(s) ***
                           ------------------------------------------

6.   Any commercial interest shown at this stage?  Name companies and specific
     persons if possible.

***
--------------------------------------------------------------------------------
________________________________________________________________________________
________________________________________________________________________________

     a.   Do you know of other qualified firms?  Please list.
                                                             -------------------

***
--------------------------------------------------------------------------------
________________________________________________________________________________

7.   Name(s) and title(s) of inventor(s)

     a.   ***
          ----------------------------------------------------------------------

     b.   ***
          ----------------------------------------------------------------------

     c.
          ______________________________________________________________________

(Contract for more data       ***                  Telephone        ***
                        -------------------------               --------------
                              (name)

                                      -4-

*** Confidential treatement requested
<PAGE>

8.   Mailing address for inventor(s) ***
                                     ----------------------------------

***
--------------------------------------------------------------------------------
(street and number)               (city and state)               (zip code)

9.   Signature(s) of inventor(s) and date

     a.   /s/ ***                      ***                     (date) ***
          ----------------------------------------------------        ---------

     b.   /s/ ***                      ***                     (date) ***
          ----------------------------------------------------        ---------

     c.                                                        (date)
          ____________________________________________________        ---------

     Use the space below and additional sheets to elaborate on answers to
questions and to provide any other helpful data.

*** Confidential treatment requested

                                      -5-

<PAGE>

6.   ***

***

***

*** Confidential treatment requested

                                      -6-<PAGE>

[CONFIDENTIAL TREATMENT REQUESTED. CONFIDENTIAL PORTIONS OF THIS AGREEMENT HAVE
BEEN REDACTED AND HAVE BEEN SEPARATELY FILED WITH THE COMMISSION.]

                                                                   Exhibit 10.11

                    FIRST AMENDMENT TO THE AGREEMENT ENTITLED
                  "ASSIGNMENT OF PATENT RIGHTS AND TECHNOLOGY"
                       ENTERED INTO AUGUST 1, 1991 BETWEEN
         THE UNIVERSITY OF TEXAS, ADAM HELLER, AND E. HELLER AND COMPANY
                                (THE "AMENDMENT")

        WHEREAS, under the August 1, 1991, agreement entitled "Assignment of
Patent Rights and Technology" (hereafter "Assignment"), and Exhibit A hereto,
the Board of Regents of the University of Texas System on behalf of The
University of Texas at Austin (hereafter collectively referred to as "Assignor")
assigned to E. Heller and Company ("Assignee") its right, title, and interest
in, to, and under the Patent Rights and the Technology (as such terms are
defined in the Assignment); and

        WHEREAS, under Paragraph 3.1 of the Assignment the parties agreed that
in return for its assignment of rights, Assignor would be compensated as noted
in the event Patent Rights, the Technology, and the Know-How are sold, licensed,
or otherwise disposed of for value to a third party or parties; and under
Paragraph 3.2 of the Assignment the parties also agreed that Assignor would be
compensated for a to-be-negotiated amount should Assignee elect to itself
manufacture, sell, or otherwise dispose of for value Licensed Products and
Licensed Processes (as such terms are defined in the Assignment) and which are
derived from the Patent Rights, the Technology, and the Know-How; and

        WHEREAS, since the effective date of the Assignment, Assignee has
invested approximately *** in research and development of biosensors
within the scope of the Technology, Patent Rights, and Know-How, and estimates
that an additional investment of approximately *** will be necessary to
complete product development and enter into clinical trials, and Assignee, on
behalf of itself and its Affiliates (as defined below), has now elected to
manufacture, sell, or otherwise dispose of for value, including sublicensing,
the Patent Rights, Technology, Know-How, Licensed Products, and Licensed
Processes; and

        WHEREAS, Assignor and Assignee now desire to amend Paragraphs 3.1 and
3.2 and certain other paragraphs of the Assignment and specifically set out
herein the mutually agreed compensation due Assignor for Assignee's disposition
for value of the Patent Rights, the Technology, the Know-How, Licensed Products
and Licensed Processes.

        NOW, THEREFORE, in consideration of the covenants and agreements
herein contained the parties agree as follows:

1.      All capitalized terms not defined in this Amendment shall have the
        meaning given to them in the Assignment.

2.      Section 1.2 is amended to read in its entirety as follows:

        1.2  Patent Rights. The term "Patent Rights" as used herein shall mean
             -------------
        Assignor's rights in all inventions and intellectual property disclosed
        in the patent applications patents and other invention disclosures
        listed on Exhibit B and Exhibit C hereto, including all U.S. and

*** Confidential treatment requested
<PAGE>

         foreign patent applications including provisional applications, and all
         divisions, continuations, continuations in-part, and substitutions
         thereof; all foreign patent applications corresponding to the preceding
         applications; and all U.S. and foreign patents issuing on any of the
         preceding applications, including extensions, reissues, and re-
         examinations.

3.       Section 1.3 is amended to read in its entirety as follows:

         1.3   Know-How. The term "Know How" as used herein shall mean
               --------
         Assignor's rights in all ideas, inventions, data, trade secrets,
         instructions, processes, formulas, chemical, pharmacological,
         toxicological, pharmaceutical, physical and analytical, manufacturing
         (including but not limited to processes, yields, reagants and
         conditions relating to compound manufacture) data and information,
         owned or controlled by Assignor existing as of the last signature date
         of this Assignment which are generally not known, and which are
         necessary or useful for the manufacture of Licensed Products. Excluded
         from Know-How are any inventions included with Patent Rights.

4.       Section 1.4 is amended to read in its entirety as follows:

         1.4   Licensed Products. The term "Licensed Products" as used herein
               -----------------
         shall mean any product which (i) is covered by a Valid Claim in the
         country such product is made or sold, or (ii) incorporates in material
         part or is made using the Technology, Know-How, Licensed Processes or
         Other Intellectual Property. For the avoidance of doubt, subject to the
         foregoing, a Licensed Product unit shall mean any instrument or
         associated disposable.

5.       Article 1 is amended to add new Section 1.7 as follows:

         1.7   Affiliate. The term "Affiliate" as used herein shall mean any
               ---------
         corporation or other entity which is directly or indirectly
         controlling, controlled by or under the common control with a party
         hereto. For the purposes of this definition, "control" shall mean the
         direct or indirect ownership of at least fifty percent (50%) of the
         outstanding shares or other voting rights of the subject entity to
         elect directors, or if not meeting the preceding, any entity owned or
         controlled by or owning or controlling at the maximum control or
         ownership right permitted in the country where such entity exists.

6.       Article 1 is amended to add new Section 1.8 as follows:

         1.8   Net Sales. The term "Net Sales" as used herein shall mean the
               ---------
         gross revenues received by Assignee, its Affiliates or sublicensees
         from sales of Licensed Products, less (i) normal and customary rebates,
         and cash and trade discounts, actually taken, (ii) sales, value-added,
         use and/or other excise taxes or duties actually paid, (iii) outbound
         transportation charges prepaid or allowed, (iv) import and/or export
         duties actually paid, and (v) amounts allowed or credited due to
         returns.

7.       Article 1 is amended to add new Section 1.9 as follows:

         1.9   Valid Claim. The term "Valid Claim" as used herein shall mean (i)
               -----------
         a claim of an issued and unexpired patent included within the Patent
         Rights which has not been disclaimed

                                      -2-
<PAGE>

         or admitted to be invalid or unenforceable through reissue or
         otherwise, or (ii) a claim of a pending application within the Patent
         Rights provided that not more than five (5) years have elapsed from the
         date the claim takes priority for filing purposes.

8.       Article 1 is amended to add new Section 1.10 as follows:

         1.10  Dominating Patent. The term "Dominating Patent" as used herein
               -----------------
         shall mean an unexpired patent which is owned by a third party covering
         Licensed Products made and sold by Assignee or its sublicensees under
         circumstances such that Assignee or its sublicensee has no commercially
         reasonable alternative but to obtain a license under such patent in
         order to make, use or commercialize a Licensed Product.

9.       Article 1 is amended to add new Section 1.11 as follows:

         1.11  Other Intellectual Property. The term "Other Intellectual
               ---------------------------
         Property" as used herein shall mean Board's rights in any biosensor
         related inventions (whether or not patentable), improvements,
         discoveries, developments, original works of authorship, software,
         trade secrets, Know-How made, conceived, reduced to practice or
         otherwise developed, by an employee of Assignor pursuant to either (i)
         a consulting agreement entered into by such employee and EHC or its
         sublicensee; or (ii) any similar agreement between an employee of the
         University of Texas at Austin and Assignee, and all intellectual
         property rights therein and thereto, shall be subject to the Assignment
         in Section 2.1 below.

10.      Section 2.1 is amended to read in its entirety as follows:

         2.1   Assignment by Assignor. Assignor hereby transfers, assigns,
               ----------------------
         sells, and conveys to Assignee, its successors and assigns, the entire
         right, title and interest throughout the world in and to the Patent
         Rights, Technology, Know-How, and Other Intellectual Property subject
         only to: (a) any rights of the United States Government which may exist
         now or in the future due to a research funding agreement to which the
         United States Government may be a party; and (b) the terms and
         conditions of this Agreement.

11.      Article 3 is amended to read in its entirety as follows:

         3.1   Royalties. In consideration for the Assignment herein, Assignee
               ---------
         shall pay to Assignor the greater of (i) an annual minimum royalty of
         *** or (ii) royalties on Net Sales of Licensed Products sold by
         Assignee, an Affiliate or its sublicensees which are within the scope
         of a Valid Claim as follows:

                                      Numbers of Licensed
         Royalty Rate                 Products Sold Worldwide During the Term
         ------------                 ---------------------------------------

         ***  of Net Sales            1-100,000

         ***  of Net Sales            100,001-200,000

         ***  of Net Sales            200,001-and above

                                      -3-
<PAGE>

         Any minimum annual royalty payable hereunder shall be ***
         against any running royalty payable to Assignor during such year.

         3.2   Sublicense Payment. In addition to the royalties subject to
               ------------------
         Section 3.1 above, Assignee shall pay to Assignor *** received by
         Assignee and its Affiliates from licensees and sublicensees of the
         Patent Rights, Know-How, Technology or Other Intellectual Property.
         Notwithstanding the foregoing, it is understood and agreed that
         Assignor shall not be entitled to any portion of amounts received from
         licensees or sublicensees for equity in Assignee less than *** of
         fair market value, debt financing, research and development funding,
         the license or sublicense of any intellectual property other than the
         Patent Rights, Know-how, Technology or Other Intellectual Property, or
         reimbursement for patent or other expenses, and to be determined in a
         manner consistent with generally accepted accounting principles (GAAP).

         3.3   Royalties on Combination Products. In the event that a Licensed
               ---------------------------------
         Product is sold by Assignee, an Affiliate or its sublicensee in
         combination as a single product with another product whose sale and use
         are not within the scope of a Valid Claim in the country for which the
         combination product is sold, Net Sales from such sales for purposes of
         calculating the amounts due under Section 3.1 above shall be calculated
         by multiplying the Net Sales of that combination by the fraction A/(A +
         B), where A is the gross selling price of the Licensed Product sold
         separately and B is the gross selling price of the other product sold
         separately. In the event that no such separate sales are made by
         Assignee, an Affiliate or its sublicensee, Net Sales for royalty
         determination shall be as reasonably allocated by Assignee, an
         Affiliate or its sublicensee between such Licensed Product and such
         other product, based upon their relative importance and proprietary
         protection. Notwithstanding the above, in no event shall Assignor
         receive a royalty of less *** the running royalty amount per unit of
         Licensed Product due under Section 3.1 above.

         3.4   Third Party Royalty Offset. In the event Assignee, an Affiliate
               --------------------------
         or its sublicensee enters into a license agreement with any third party
         with respect to a Dominating Patent or to settle a claim of
         infringement or misappropriation of any intellectual property of a
         third party relating to the practice or use of the Technology and or
         Know-How, Assignee, an Affiliate or its sublicensee may offset any
         payments made in accordance with such license agreements against any
         amounts of running royalties owned by Assignee pursuant to Article 3
         herein up to a maximum of *** the amount otherwise due to such third
         party; provided, however that in no event will the running royalties
         due to Assignor be lower than the following:

         Royalty Rate                Number of Licensed Products Sold Worldwide
         ------------                ------------------------------------------
                                     During the Term
                                     ---------------

         ***  of Net Sales           1-100,000

         ***  of Net Sales           100,001-200,000

         ***  of Net Sales           200,001 - and above

                                      -4-

***  Confidential treatment requested
<PAGE>

         In addition, in such event, the amounts due to Assignor under Section
         3.2 above shall be reduced by an amount equal to *** the amount paid
         to such third party.

         3.5   One Royalty. No more than one royalty payment shall be due with
               -----------
         respect to a sale of a particular Licensed Product. No multiple
         royalties shall be payable because any Licensed Product, or its
         manufacture, use or sale is covered by more than one Valid Claim. No
         royalty shall be payable under this Article 3 with respect to Licensed
         Products distributed for use in research and/or development, in
         clinical trials or as promotional samples.

         3.6   Royalty Term. Royalties due under this Article 3 shall be payable
               ------------
         on a country-by-country and Licensed Product-by-Licensed Product basis
         until the expiration of the last-to-expire issued Valid Claim covering
         such Licensed Product in such country, or if no such Valid Claim issued
         in a country, until the fifth anniversary of the first commercial sale
         of a Licensed Product in such country.

         3.7   In the event Assignee engages in litigation and/or settlement
         negotiations to advance a claim it makes that a third party is
         infringing on Licensed Products and/or Licensed Processes, ***
         on any litigation or settlement recovery by Assignee will be paid to
         Assignor; provided, however, that Assignee shall be entitled to first
         deduct reasonable and documented attorney's and other professional
         fees, expert fees, court costs, and other reasonable expenses incurred
         by Assignee in such litigation and/or settlement activities.

12.      Section 4.2 is amended to read in its entirety as follows:

         4.2   Payments and Reports. The first annual minimum royalty payment of
               --------------------
         *** shall be due and payable to Assignor within 30 days of the date of
         the last signature on this Amendment. Thereafter, minimum annual
         royalty payments, when due, shall be due and payable within thirty (30)
         days after the end of the applicable year. All running royalties
         payable hereunder by Assignee shall be due within thirty (30) days
         following the end of each respective semi-annual reporting period,
         which ending dates shall be June 30 and December 31 for each successive
         year. Each report will accurately identify income and expenses in
         sufficient form and detail so as to enable Assignor to determine the
         royalties due for such semi-annual period, and shall be mailed to the
         following: Office of the Executive Vice President and Provost, The
         University of Texas at Austin, Main Building 201, Austin, Texas 78712-
         1111, ATTN: Patricia C. Ohlendorf, with a copy to the Office of
         Technology Licensing and Intellectual Property at the address listed in
         16.3 herein. Checks shall be made payable to The University of Texas at
         Austin. Except as expressly provided herein, all amounts payable
         hereunder shall be payable in United States dollars without deductions
         for taxes, assessments, fees, or charges of any kind.

13.      Article 15 is amended to read in its entirety as follows:

         15.1  Assignment. Neither party may assign this Assignment without the
               ----------
         prior consent of the other, which consent shall not be unreasonably
         withheld; provided, however, Assignee may assign this Assignment in
         connection with a transfer of all or substantially all of its

***  Confidential treatment requested

                                      -5-

<PAGE>

     assets relating to this Assignment, whether by sale, merger, operation of
     law or otherwise. This Assignment shall be binding upon and inure to the
     benefit of the parties and their successors and assigns.

14.  New Article 16 is added as follows:

     MISCELLANEOUS
     -------------

     16.1  Affiliate Rights/Obligations. Assignee shall have the right to extend
           ----------------------------
     the provisions of the Assignment regarding the right to manufacture, sell,
     or otherwise dispose of for value, including licensing and sublicensing,
     the Patent Rights, Technology, Know-How, Other Intellectual Property,
     Licensed Products, and Licensed Processes, to any Affiliate, provided such
     Affiliate consents to be bound by the Assignment to the same extent as
     Assignee. Further, Assignee shall have the right to extend the provisions
     of this Amendment in their entirety to any Affiliate, provided such
     Affiliate consents to be bound by the applicable provisions of this
     Amendment to the same extent as Assignee.

     16.2  Entire Agreement. The Assignment and this Amendment constitute the
           ----------------
     entire and only agreement between the parties with respect to the Patent
     Rights, Technology, Know-How, Other Intellectual Property, Licensed
     Products, and Licensed Processes, and all other prior negotiations,
     representations, agreements, and understandings are superseded hereby. No
     agreement altering or supplementing the terms of the Assignment may be made
     except by means of a written document signed by a duly authorized
     representative of each party.

     16.3. Notices. Any notices under this Assignment or shall be given by
           -------
     prepaid, first class, certified mail, return receipt requested, addressed
     as follows (or such other address as may be given from time to time under
     the terms of this provision):

<TABLE>
     <S>                                            <C>
     in the case of Assignor -                       with a copy to -
     BOARD OF REGENTS                                OFFICE OF THE EXECUTIVE
     The University of Texas System                  VICE PRESIDENT & PROVOST
     201 West 7th Street                             The University of Texas at Austin
     Austin, Texas  78701                            Austin, Texas 78712-1111
     ATTN: System Intellectual Property Office       ATTN:  Patricia C. Ohlendorf

                                                     with a copy to -
                                                     OFFICE OF TECHNOLOGY LICENSING AND
                                                     INTELLECTUAL PROPERTY
                                                     The University of Texas at Austin
                                                     MCC Building
                                                     Suite 1.9A
                                                     3925 West Braker Lane
                                                     Austin, Texas  78759
                                                     ATTN:  Director
</TABLE>

                                      -6-
<PAGE>

         or in the case of Assignee -

         E. HELLER AND COMPANY
         1311 Harbor Bay Parkway, Suite 1000
         Alameda, California  94502
         ATTN:  Ephraim Heller

         16.4  LIMITATION OF LIABILITY. SUBJECT TO ARTICLE XIV OF THE
               -----------------------
         ASSIGNMENT, NEITHER PARTY SHALL BE LIABLE TO THE OTHER FOR ANY SPECIAL,
         CONSEQUENTIAL, INCIDENTAL OR INDIRECT DAMAGES ARISING OUT OF THIS
         ASSIGNMENT, HOWEVER CAUSED, UNDER ANY THEORY OF LIABILITY

         16.5  Right to Independently Develop. Nothing in this Assignment will
               ------------------------------
         impair Assignee's right to independently acquire, license, develop for
         itself, or have others develop for it, technology or intellectual
         property performing the same or similar functions as the Know-How or
         the Patent Rights, or the Other Intellectual Property, or to market and
         distribute licensed products based on such other intellectual property
         and technology.

         16.6  Further Assurances. At any time or from time to time on and after
               ------------------
         the date of this Assignment, Assignor shall at the request and sole
         expense of Assignee (i) deliver to Assignee such records, data or other
         documents consistent with the provisions of this Assignment, (ii)
         execute, and deliver or cause to be delivered, all such consents,
         documents or further instruments of transfer or license, and (iii) take
         or cause to be taken all such actions, as Assignee may reasonably deem
         necessary or desirable in order for Assignee to obtain the full
         benefits of the Assignment and Amendment and the transactions
         contemplated hereby.

         16.7  Severability. In the event that any provisions of this Assignment
               ------------
         are determined to be invalid or unenforceable by a court of competent
         jurisdiction, the remainder of the Assignment shall remain in full
         force and effect without said provision. The parties shall in good
         faith negotiate a substitute clause for any provision declared invalid
         or unenforceable which shall most nearly approximate the intent of the
         parties in entering this Assignment.

         16.8  Modification; Waiver. This Assignment may not be altered, amended
               --------------------
         or modified in any way except by a writing signed by both parties. The
         failure of a party to enforce any provision of the Assignment shall not
         be construed to be a waiver of the right of such party to thereafter
         enforce that provision or any other provision or right.

15.      Except as specifically modified or amended hereby, the Assignment shall
         remain in full force and effect and, as so modified or amended, is
         hereby ratified, confirmed and approved. No provision of this Amendment
         may be modified or amended except expressly in a writing signed by both
         parties nor shall any terms be waived except expressly in a writing
         signed by the party charged therewith. This Amendment shall be governed
         in accordance with the laws of the State of Texas, without regard to
         principles of conflicts of laws.

                                      -7-
<PAGE>

         IN WITNESS WHEREOF, this Amendment effective as of March 19, 1998, is
hereby executed by the duly authorized representatives of the parties on the
date indicated below in duplicate, each of which shall be deemed an original and
together shall form one and the same instrument.

BOARD OF REGENTS OF THE
UNIVERSITY OF TEXAS SYSTEM                       E. HELLER AND COMPANY

/s/ Ray Farabee                                  /s/ Ephraim Heller
---------------------------------------          -------------------------------
Ray Farabee                                      Ephraim Heller
Vice Chancellor and General Counsel              President
Date:   4/7/98                                   Date:   3/19/98
     ----------------------------------               --------------------------

APPROVED AS TO CONTENT                           ADAM HELLER

/s/ Patricia C. Ohlendorf                        /s/ Adam Heller
---------------------------------------          -------------------------------
Patricia C. Ohlendorf                            Adam Heller
Counsel to the President                         Date:   3/19/98
                                                      --------------------------
Vice Provost
Date:   3/27/98
     ----------------------------------

APPROVED AS TO FORM

/s/ Georgia Harper
---------------------------------------

Name: Georgia Harper
     ----------------------------------
Office of General Counsel
Date: 4/7/98
     ----------------------------------

                                      -8-
<PAGE>

                                   EXHIBIT B

                                 (See attached)
<PAGE>

COLLEGE OF ENGINEERING

THE UNIVERSITY OF TEXAS AT AUSTIN

Department of Chemical Engineering, Austin, Texas 78712-1062

Adam Heller                                                     January 6, 1997
Ernest Cockrell, Sr. Chair
Telephone:      (512) 471-8874
FAX:            (512) 471-8799
e-mail:         heller@che.utexas.edu

To:             Dr. Paulette Braeutigam, Technology
                    Licensing Coordinator

From:           Adam Heller

Dear Paulette:

This letter follows your discussion with Ephraim wherein you agreed to cover in
the current agreement between The University of Texas at Austin and E. Heller &
Company all presently existing intellectual property relating to biosensors that
originated in my group. These include the following:

US Patents Issued:
-----------------

The already issued patents are:

US 5,543,326 - Biosensor including chemically modified enzymes.

US 5,356,786 - Interferant eliminating biosensor

US 5,320,725 - Electrode and Method for the detection of hydrogen peroxide.

US 5,264,105 - Enzyme electrodes.

US 5,264,104 - Enzyme electrodes.

US 5,262,305 - Interferant eliminating biosensor.

US 5,262,035 - Enzyme electrodes.

<PAGE>

US Patents Currently Prosecuted:
-------------------------------

(1)    ***

                                      -2-

*** Confidential treatment requested
<PAGE>

***

*** Confidential treatment requested

                                      -3-
<PAGE>

***

*** Confidential treatment requested

                                      -4-
<PAGE>

***

*** Confidential treatment requested

                                      -5-
<PAGE>

***

*** Confidential treatment requested
                                      -6-

<PAGE>

***

With my regards and best wishes for 1997.

Adam Heller

AH:n

*** Confidential treatment requested

                                      -7-

<PAGE>

                                   EXHIBIT B

EXECUTIVE VICE PRESIDENT AND PROVOST

THE UNIVERSITY OF TEXAS AT AUSTIN

Main Building 201, Austin, Texas 78712-1111

                                 August 1, 1991

Dr. Adam Heller
Department of Chemical Engineering
CPE 4.450

Re:    UTSB:413 - "Enzyme Electrodes"
       UTSB:465 - "Inteferant Eliminating Biosensors"

Dear Dr. Heller:

       I write to followup our previous communications regarding your request
that The University exclusively license or release to you the inventions
entitled UTSB:413 and UTSB:465, which you co-invented. I am setting out below
conditions under which The University will release and/or assign to you, as
appropriate, its intellectual property rights in the subject matter presently
described in patent applications UTSB:413 and UTSB:465, and any subject matter
that may in the future be included in a continuation, continuation-in-part, or
divisional, to these patent applications. These conditions are consistent with
similar arrangements into which The University has entered:

       (1)      You (or your company) will pay The University a nonrefundable
                fee of [Thirty Thousand Dollars ($30,000)] by September 1, 1991.
                These funds shall be used by The University to pay patent
                expenses that we have thus far incurred on these cases. In the
                unlikely event that funds remain after deduction of those
                expenses, we shall share with your coinventors the proportion of
                the [fifty percent (50%)] inventors' share that each would
                receive were you still included among the inventors who share in
                The University's income;

       (2)      Effective August 1, 1991, you (or your company) shall assume all
                financial and decision making responsibility for maintenance and
                prosecution of these patent applications and any patents that
                issue, including foreign counterparts. The University shall
                inform Arnold, White & Durkee of this shift in responsibility.
                Should you wish to have the cases transferred from Arnold, White
                & Durkee to your own attorney, The University will cooperate in
                this transfer subject to reimbursement of any associated
                expenses above [$300.00;]

Source: [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00016-of-00352.parquet"}, [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00016-of-00352.parquet"}]]