Exhibit 10.48


               ADDENDUM TO DEED OF TRUST WITH ASSIGNMENT OF RENTS

        THIS ADDENDUM to that certain Deed of Trust With Assignment of Rents by
______________ ("Employee") and ______________, husband and wife (hereinafter
referred to collectively as "Trustor"), in favor of INVITROGEN CORPORATION, a
Delaware corporation (hereinafter referred to as "Beneficiary") (the "Deed of
Trust"), is dated as of the same date as the Deed of Trust and incorporates,
amends and modifies the Deed of Trust as follows:

        1. Acceleration of Indebtedness. If Trustor shall sell, convey, lease or
otherwise alienate the property, or any part thereof, or any interest therein,
or shall be divested of its title or any interest therein in any manner or way,
whether voluntarily or involuntarily, without the written consent of Beneficiary
being first had and obtained, then Beneficiary shall have the right, at its
option, except as prohibited by law, to declare any indebtedness or obligations
secured hereby, irrespective of the maturity date specified in any note
evidencing the same, immediately due and payable.

        2. Security for Repayment of a Promissory Note. The Deed of Trust
secures the repayment of a Secured Promissory Note of even date herewith in the
original principal amount of U.S. _______________________ Thousand Dollars
(U.S.$_________) (the "Note"). The Note contains the following provisions:


                9. Default/Acceleration. At the option of the holder, without
           prior notice, and regardless of any prior forbearance, all sums
           remaining unpaid under this Note shall become immediately due and
           payable upon the occurrence of a default by Makers under this Note.
           The occurrence of any of the following events shall constitute a
           default by Makers under this Note:

                   9.1 Makers' failure to pay any payment of interest or
           principal when due under this Note, including, without limitation,
           Makers' failure to satisfy in full all sums remaining unpaid under
           this Note on or before the Maturity Date; or

                   9.2 Makers' failure to perform any of Makers' other monetary
           and nonmonetary covenants and agreements contained in this Note or
           the Deed of Trust.

        3. Termination of Employment. The Note secured by the Deed of Trust also
contains the following provision pertaining to Trustor's termination of
employment:

                   12. Termination of Employment. In the event Employee's
            employment with [Beneficiary] is terminated voluntarily or is
            terminated involuntarily for Cause, (i) the outstanding principal
            balance of this Note


                                       1


               shall thereafter bear interest at the fixed rate described
               in Section 1 above (subject to the limitations described in
               Subsections 1.2) and (ii) all sums remaining unpaid under this
               Note shall become due and payable on the date set forth in
               Section 3 above, unless sooner accelerated or unless forgiven
               pursuant to Subsection 3.2 or Section 4 above.

        4. Maturity of Note. Pursuant to Section 3.1 of the Note, the
"outstanding principal amount of the indebtedness evidenced by this Note shall
be due and payable on the date 180 days after the voluntary termination (e.g.,
resignation) of Employee's employment with Invitrogen or 180 days after
Employee's involuntary termination for Cause (either of such dates referred to
herein as the "Maturity Date")."

        5. Subordinate Lien. The lien of the Deed of Trust shall be junior and
subordinate to a first priority lien of a deed of trust, recorded on
______________, 2002, as Document No. 2002-__________ in the Official Records of
San Diego County, in favor of _________________________________, securing
indebtedness in the original principal amount of $_________.

                                     TRUSTOR:

                                     -------------------------------------
                                     [Add name]


                                     -------------------------------------
                                     [Add name]


                                       2


[This notarial acknowledgment is attached as page 3 to that certain Addendum to
Deed of Trust With Assignment of Rents]

STATE OF                           }
                                         ss
COUNTY OF

On ______________, 2002, before me, _______________________________ the
undersigned Notary Public, personally appeared _______________________ [ ]
personally known to me, or [ ] proved to me on the basis of satisfactory
evidence to be the person(s) whose name(s) is/are subscribed to the within
instrument, and acknowledged to me that he/she/they executed the same in
his/her/their authorized capacity(ies), and that by his/her/their signature(s)
on the instrument the person(s), or the entity upon behalf of which the
person(s) acted, executed the instrument.

WITNESS my hand and official seal.

                                         --------------------------------------
(SEAL)                                   Signature of Notary Public


                                       3


[This notarial acknowledgment is attached as page 4 to that certain Addendum to
Deed of Trust With Assignment of Rents]

STATE OF                           }
                                         ss

COUNTY OF

On ______________, 2002, before me, _____________________________ the
undersigned Notary Public, personally appeared ________________________ [ ]
personally known to me, or [ ] proved to me on the basis of satisfactory
evidence to be the person(s) whose name(s) is/are subscribed to the within
instrument, and acknowledged to me that he/she/they executed the same in
his/her/their authorized capacity(ies), and that by his/her/their signature(s)
on the instrument the person(s), or the entity upon behalf of which the
person(s) acted, executed the instrument.

WITNESS my hand and official seal.


                                         --------------------------------------
(SEAL)                                   Signature of Notary Public



                                       4