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                                                                   EXHIBIT 10.15

                              PROMISSORY NOTE NO. 7
                              ---------------------
                                    1170-007

                                                        Date: September 29, 2000


     FOR  VALUE RECEIVED, the undersigned promises to pay to the order of
Transamerica Business Credit Corporation or its assigns (the "Payee") at its
office located at Riverway 11, West Office Tower, 9399 West Higgins Road,
Rosemont, Illinois 60018, or at such other place as the Payee or the holder
hereof may designate in writing, the principal amount of Nine Hundred Fifty
Thousand, One Hundred Twenty and 43/100 Dollars ($950,120.43) received by the
undersigned, plus interest, in lawful money of the United States and in
immediately available funds. This Note shall be payable on the date hereof and
thereafter in 48 consecutive equal monthly installments of Twenty Three
Thousand, One Hundred Fifty Five and 39/100 Dollars ($23,155.39) commencing
October 1, 2000 and a final installment payable on October 1, 2004 of Ninety
Five Thousand, Twelve and 04/100 Dollars ($95,012.04) together with the unpaid
balance of the Note. No amount of principal paid or prepaid hereunder may be
reborrowed

     This Note is one of the Notes referred to in the Master Loan and Security
Agreement dated as of October 26, 1998 (as amended, supplemented or otherwise
modified from time to time, the "Agreement"), between the undersigned and the
Payee and is subject and entitled to all provisions and benefits thereof.
Capitalized terms used but not defined herein shall have the meanings set forth
in the Agreement.

     If any installment of this Note is not paid within six days after its due
date, the undersigned agrees to pay on demand, in addition to the amount of such
installment, an amount equal to 4% of such installment, but only to the extent
permitted by Applicable Law.

     The undersigned shall have the right to prepay this Note at any time on or
after January 1, 2002, on thirty days' prior written notice to the Payee. On the
date of any such prepayment, the undersigned shall pay an amount equal to the
present value of the remaining payments (principal and interest) due hereunder
discounted at 7% simple interest per annum together with all interest, fees and
other amounts payable on the amount so prepaid or in connection therewith to the
date of such prepayment. Any prepayments shall be applied to the installments
hereof in the inverse order of maturity.

     Upon the maturity of this Note or the acceleration of the maturity of this
Note in accordance with the terms of the Agreement, the entire unpaid principal
amount on this Note, together with all interest, fees and other amounts payable
hereon or in connection herewith, shall be immediately due and payable without
further notice or demand, with interest on all such amounts at a rate not to
exceed the lesser of (i) 18% per annum or (ii) the maximum amount allowed by
law, from the date of such maturity or acceleration, as the case may be, until
all such amounts have been paid. Upon default or the acceleration of the
maturity of this Note in accordance with the terms of the Agreement, the entire
unpaid principal amount on this Note, together with all interest, fees,
prepayment fees and charges in an amount equal to the present value of the
remaining payments (principal and interest) due hereunder discounted at 6%
simple interest per annum and other amounts payable hereon or in connection
herewith, shall be immediately due and payable without further notice or demand,
with interest on all such amounts at a rate not to exceed the lawful limit, from
the date of such maturity, default or acceleration, as the case may be, until
all such amounts have been paid.

     If any payment on this Note becomes payable on a day other than a
Business Day, the maturity thereof shall be extended to the next succeeding
Business Day.

     The undersigned hereby waives diligence, demand, presentment, protest and
notice of any kind, and assents to extensions of the time of payment, release,
surrender or substitution of security, or forbearance or other indulgence,
without notice. The undersigned agrees to pay all amounts under this Note
without offset, deduction, claim, counterclaim, defense or recoupment, all of
which are hereby waived.

     The Payee, the undersigned and any other parties to the Loan Documents
intend to contract in strict compliance with applicable usury law from time to
time in effect. In furtherance thereof such Persons stipulate
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and agree that none of the terms and provisions contained in the Loan Documents
shall ever be construed to create a contract to pay, for the use, forbearance or
detention of money, interest in excess of the maximum amount of interest
permitted to be charged by Applicable Law from time to time in effect. Neither
the undersigned nor any present or future guarantors, endorsers, or other
Persons hereafter becoming liable for payment of any Obligation shall ever be
liable for unearned interest thereon or shall ever be required to pay interest
thereon in excess of the maximum amount that may be lawfully charged under
Applicable Law from time to time in effect, and the provisions of this paragraph
shall control over all other provisions of the Loan Documents which may be in
conflict or apparent conflict herewith. The Payee expressly disavows any
intention to charge or collect excessive unearned interest or finance charges in
the event the maturity of any Obligation is accelerated. If (a) the maturity of
any Obligation is accelerated for any reason, (b) any Obligation is prepaid and
as a result any amounts held to constitute interest are determined to be in
excess of the legal maximum, or (c) the Payee or any other holder of any or all
of the Obligations shall other-wise collect amounts which are determined to
constitute interest which would otherwise increase the interest on any or all of
the Obligations to an amount in excess of that permitted to be charged by
Applicable Law then in effect, then all sums determined to constitute interest
in excess of such legal limit shall, without penalty, be promptly applied to
reduce the then outstanding principal of the related Obligations or, at the
Payee's or such holder's option, promptly returned to the undersigned upon such
determination. In determining whether or not the interest paid or payable, under
any specific circumstance, exceeds the maximum amount permitted under Applicable
Law, the Payee and the undersigned (and any other payors thereof) shall to the
greatest extent permitted under Applicable Law, (i) characterize any
non-principal payment as an expense, fee or premium rather than as interest,
(ii) exclude voluntary prepayments and the effects thereof, and (iii) amortize,
prorate, allocate, and spread the total amount of interest through the entire
contemplated term of this Note in accordance with the amount outstanding from
time to time thereunder and the maximum legal rate of interest from time to time
in effect under Applicable Law in order to lawfully charge the maximum amount of
interest permitted under Applicable Law.

     This Note may not be changed, modified or terminated orally, but only by an
agreement in writing signed by the undersigned and the Payee or any holder
hereof.

     The undersigned shall, upon demand, pay to the Payee all costs and
expenses incurred by the Payee (including the reasonable fees and disbursements
of counsel and other professionals) in connection with the preparation,
execution and delivery of this Note and all other Loan Documents (which costs
and expenses shall not exceed $5,000 without the consent of the undersigned),
and in connection with the administration, modification and amendment of the
Loan Documents, and pay to the Payee all costs and expenses (including the fees
and disbursements of counsel and other professionals) paid or incurred by the
Payee in (A) enforcing or defending its rights under or in respect of this Note
or any of the other Loan Documents, (B) collecting any of the liabilities by the
undersigned to the Payee or otherwise administering the Loan Documents, (C)
foreclosing or otherwise collecting upon any collateral and (D) obtaining any
legal, accounting or other advice in connection with any of the foregoing. Of
the $50,000 Application Fee paid by the undersigned to the Payee, after
application of up to $5,000 to costs and expenses incurred in closing the
transaction governed by the Agreement, a portion of the remaining amount (as set
forth in the Commitment Letter) shall be applied to the second installment due
hereunder.

     This Note shall be binding upon the successors and assigns of the
undersigned and inure to the benefit of the Payee and its successors, endorsees
and assigns. If any term or provision of this Note shall be held invalid,
illegal or unenforceable, the validity of all other terms and provisions hereof
shall in no way be affected thereby.

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THIS NOTE IS BEING DELIVERED TO PAYEE BY THE UNDERSIGNED TO EVIDENCE A LOAN FROM
PAYEE TO THE UNDERSIGNED WHICH LOAN IS SECURED BY AMONG OTHER THINGS THE
EQUIPMENT DESCRIBED ON SCHEDULE A ATTACHED HERETO.

EACH OF THE UNDERSIGNED AND, BY ITS ACCEPTANCE HEREOF, THE PAYEE HEREBY
KNOWINGLY, VOLUNTARILY AND INTENTIONALLY WAIVES (TO THE FULLEST EXTENT PERMITTED
BY APPLICABLE LAW) ANY RIGHT IT MAY HAVE TO A TRIAL BY JURY OF ANY DISPUTE
ARISING UNDER OR RELATING TO THIS NOTE AND AGREES THAT ANY SUCH DISPUTE SHALL BE
TRIED BEFORE A JUDGE SITTING WITHOUT A JURY.

THIS NOTE SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE
STATE OF ILLINOIS WITHOUT GIVING EFFECT TO PRINCIPLES OF CONFLICTS OF LAW.

                                     LYNX THERAPEUTICS, INC.

                                     By: /s/ Edward C. Albini
                                         -------------------------------
                                     Name:  Edward C. Albini
                                     Title: Chief Financial Officer