Document:

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                                                                   EXHIBIT 10.43

                            [INVITROGEN LETTERHEAD]

                                 INTERNAL MEMO

DATE      May 31, 2002

  TO      C. Eric Winzer

  CC      Lyle Turner

FROM      Jim Runchey

  RE      PROMOTION & RELOCATION

We are pleased to confirm your promotion to the position of Chief Financial
Officer, reporting to Lyle Turner, President & CEO. In this position, which
resides in Carlsbad, CA, you will be responsible for the Company's Treasury,
Tax, Financial Analysis and Reporting, IT, and Investor Relations functions. The
effective date of the promotion was May 1, 2002.

In this position, your salary will be $300,000 annualized, less applicable
withholding paid in accordance with Invitrogen's normal payroll practices. This
new salary amount includes an adjustment for your automobile allowance, which
will no longer be included as a semi-monthly payment.

In addition, you will continue to be eligible to participate in Invitrogen
Corporation's Incentive Compensation Plan (ICP) for 2002. Your ICP will be
targeted at 35% of your base salary for the period eligible. The actual
incentive bonus earned will be based on individual as well as company goals and
will be paid according to the rules of the ICP, which states in part you must be
employed on the day the bonus is paid to receive the bonus.

As an employee relocating to Carlsbad from Maryland you will be eligible for
relocation assistance as outlined in the attached Relocation Guidelines and
highlighted below:

-    2 house hunting trips (up to 7 days each) for you and your immediate family
     to Carlsbad.

-    Professional relocation services.

-    Shipment and storage (up to 90 days) of selected household goods to
     Carlsbad.

-    Temporary living assistance up to 90 days.

-    An interest free loan of up to $150,000 to assist in the purchase of
     a house.

-    Reimbursement for all standard non-recurring closing costs on your home in
     Maryland including up to 6% sales commission.

You will continue to be eligible for all standard benefits available to other
"full-time" Invitrogen employees, including: medical, dental, life, and vision
insurance; short and long-term disability insurance; Invitrogen's 401k Plan and
Employee Stock Purchase Plan in accordance with Invitrogen's policies the
applicable plan documents and benefit plan provisions.

In addition, Invitrogen's Board of Directors' has granted options to purchase
150,000 shares of Invitrogen's common stock in accordance with an approved
Invitrogen stock option plan (the "Plan") and related option documents. Options
vest according to the terms of the Plan over 4 years.

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As an additional incentive, Invitrogen agrees to enter into a Settlement and
Retention Agreement with you in the form attached hereto pursuant to which the
Company would, under the terms of the attached agreement, pay you a total bonus
of $402,375, less applicable tax and other withholdings. One half of this bonus
or $201,188 will be paid on or before October 1, 2002 (in an effort to assist
you with your relocation to Carlsbad) and the remainder or $201,187 on or about
October 1, 2004. As part of this agreement, your current Change-in-Control
Agreement would be terminated, and you would be entitled to enter into a new
Change-in-Control Agreement, a copy of which is also attached.

Employment with Invitrogen is at-will and therefore not for a specific term and
may be terminated by either you or Invitrogen at any time without notice. The
at-will nature of employment at Invitrogen constitutes the entire agreement
between you and Invitrogen and any changes to these terms must be in writing and
signed by you and the company's President or the Vice President of Human
Resources.

We will formally announce your new title and responsibilities in June, 2002. You
will be scheduled to meet with Human Resources shortly after you relocate to
Carlsbad to review your benefits, company policies and also complete any
necessary employment, benefits, and tax forms.

We wish you continued success in this new opportunity and we appreciate your
willingness to relocate your family to Carlsbad, and look forward to working
with you.

If you have any questions, feel free to contact Vickie Motte, at x67204 or me at
x67222.

/s/                                         /s/
-------------------------------------       ---------------------------------
Lyle Turner, President & CEO                Jim Runchey, VP, Human Resources

I have read this offer letter in its entirety and agree to the terms and
conditions of employment. I understand and agree that my employment with
Invitrogen is at-will.

 Dated                                     /s/
      --------------------                 ----------------------------------
                                           C. Eric Winzer<PAGE>
                                                                   Exhibit 10.44

                       SETTLEMENT AND RETENTION AGREEMENT

This Settlement and Retention Agreement (the "Agreement") is entered into by and
between John A. Cottingham ("Executive") and Invitrogen Corporation, a Delaware
Corporation ("Invitrogen" or the "Company") and is effective as of June 7, 2002
(the "Effective Date").

WHEREAS, Executive entered into a Change-in-Control Agreement dated February 13,
1997 with Life Technologies, Inc., which was amended on October 11, 2000 (the
"Original CIC Agreement"); and

WHEREAS, Life Technologies, Inc. was merged into Invitrogen in September 2000
under Delaware law, and Invitrogen thereby acquired all of the rights and
obligations of Life Technologies, Inc. under the Original CIC Agreement; and

WHEREAS, Executive is presently entitled to exercise certain rights under the
Original CIC Agreement that would result in the termination of Executive's
employment and require the Company to make a cash payment and provide other
benefits to Executive; and

WHEREAS, the Company would like to continue to employ Executive, and Executive
would like to continue to be employed by the Company; and

WHEREAS, the Company would like to reduce the incentive for Executive to
terminate Executive's employment and provide an incentive for Executive to
remain employed by the Company.

NOW THEREFORE, in consideration of the promises, mutual covenants and agreements
contained herein and for other good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, the parties intending to be
legally bound, agree as follows:

1. Settlement Payment. The Company agrees to provide a "Settlement Payment" to
Executive, payable in two lump sum installments on the dates specified below
(the "Payment Dates"), less applicable withholdings as required by law or
regulation; provided, with respect to each installment, that Executive's
employment is not terminated prior to the respective Payment Date for such
installment by the Company for Cause (as defined below) or by Executive without
Good Reason (as defined below):

<TABLE>
<CAPTION>
               Amount                              Date
               ------                              ----
<S>                                                <C>
        a.     $163,013                            October 1, 2002
        b.     $163,013                            October 1, 2004
</TABLE>

In the event Executive's employment terminates prior to one or both of the
Payment Dates for any other reason, including but not limited to termination of
Executive's employment by the Company without Cause, Executive's resignation for
Good Reason, Executive's death or Disability (as defined below), any
outstanding, unpaid portion of the Settlement Payment will become immediately
due and payable to Executive, or his estate, as the case may be.

<PAGE>

2. At-Will. Executive acknowledges that Executive continues to be employed by
the Company as an at-will employee and that nothing in this Agreement is
intended to or should be construed to contradict, modify or alter Executive's
at-will employment status.

3. Definitions.

        a. Cause. For purposes of this Agreement, "Cause" shall mean: (i)
Executive's willful and deliberate failure or refusal to perform Executive's job
responsibilities and duties (as they existed or were assigned during the 90-day
period immediately preceding the Effective Date or as revised thereafter by
agreement of Executive and the Company), provided that Executive has been given
written notice of and a 30-day opportunity to cure such non-performance; (ii)
commission of an intentional act of fraud, embezzlement or theft by Executive in
connection with Executive's duties or in the course of Executive's employment
with the Company or its affiliated companies; (iii) causing intentional,
wrongful damage to property of the Company or its affiliated companies; (iv)
intentionally and wrongfully disclosing trade secrets or confidential
information of the Company or its affiliated companies; or (v) participating,
without the Company's express written consent, in the management of any business
enterprise that engages in substantial and direct competition with the Company
or its affiliated companies and any such act shall have been materially harmful
to the Company or its affiliated companies.

        b. Good Reason. For purposes of this Agreement, "Good Reason" shall
mean:

               i. a substantial diminution in Executive's position, authority,
duties or responsibilities (as they existed or were assigned at any time during
the 90-day period immediately preceding the Effective Date), excluding
non-substantial changes in title or office and any isolated, insubstantial and
inadvertent action not taken in bad faith that is remedied by the Company within
thirty (30) days of receiving written notice thereof from Executive;

               ii. any reduction or adverse change to Executive's compensation
and benefits in place as of the Effective Date of the Agreement or granted to
Executive by the Company thereafter, including, but not limited to, base salary,
bonuses and any other incentive compensation plans or programs; savings and
retirement plans or programs; health and welfare benefit plans, including, but
not limited to, medical, prescription, dental, disability, salary continuance,
employee life, group life, accidental death and travel accident insurance plans;
and paid vacation, excluding any isolated, insubstantial and inadvertent failure
not taken in bad faith that is remedied by the Company within thirty (30) days
of receiving written notice thereof from Executive or any reduction that is made
as part of, and is generally consistent with, a general reduction of senior
executive compensation and benefits;

               iii. the relocation of Executive's principal place of work to an
office or location more than fifty (50) miles from the location Executive was
assigned to immediately prior to the Effective Date (provided, however, that
relocation to Carlsbad, CA, shall not constitute Good Reason) or the Company
substantially increases without the prior consent of the Executive the amount of
time Executive is required to travel; and

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               iv. any failure by any successor to the Company to comply with
and satisfy Section 11, provided that such successor has received at least ten
(10) days prior written notice from the Company or Executive of the requirements
of Section 11 of this Agreement.

For the purposes of this Section 3(b), any good faith determination of "Good
Reason" made by Executive shall be conclusive.

        c. Disability. The term "Disability" means Executive's inability to
perform the essential functions of Executive's job due to a mental or physical
condition, with or without reasonable accommodation. In no event will
Executive's employment be terminated for Disability until 180 consecutive days
has elapsed and Disability has been determined by a physician selected by the
Company or its insurers and acceptable to Executive or Executive's legal
representative (such agreement as to acceptability not to be withheld
unreasonably).

        d. Date of Termination. The term "Date of Termination" means the date of
receipt of the Notice of Termination (described below) or any later date
specified therein, as the case may be; provided, however, that: (i) if
Executive's employment is terminated by the Company without Cause the Date of
Termination shall be the date the Company notifies the Executive of such
termination; and (ii) if Executive's employment is terminated by reason of death
or Disability, the Date of Termination shall be the date of Executive's death or
the effective date of the Disability, as the case may be.

4. Notice of Termination. Any termination by the Company for Cause or
resignation by Executive for Good Reason before October 1, 2004, shall be
communicated by "Notice of Termination" to the other party in accordance with
Section 13(b) of this Agreement. The "Notice of Termination" must be in writing
and set forth: (a) the facts and circumstances, in reasonable detail, claimed to
provide a basis for the termination with Cause or resignation for Good Reason;
(b) if the Date of Termination is other than the date of receipt of such notice,
the termination date (which shall be not more than thirty (30) days after the
giving of such notice). Executive or the Company's failure to set forth in the
Notice of Termination any fact or circumstance that contributes to a showing of
Good Reason or Cause, as the case may be, shall not waive any right hereunder or
preclude Executive or the Company from asserting such fact or circumstance in
enforcing Executive's or the Company's rights hereunder.

5. Independent Obligations. The Settlement Payment is in settlement of
preexisting contractual claims and shall not: (a) be reduced by any severance
received by Executive, or reduce any severance to be received by Executive, upon
termination of employment under any severance plan, policy, agreement, or
arrangement of the Company applicable to Executive or a group of employees of
the Company including the Executive, whether or not any such severance received
by Executive is payable as a result in whole or in part of a change in control
of the Company prior to such termination of employment; (b) constitute "salary,"
"bonus," or "severance" for purposes of the New CIC Agreement (described at
Section 12 below), and accordingly, shall not increase, decrease, or affect in
any way the calculation of money payable or entitlement to other benefits
pursuant to the New CIC Agreement; (c) be affected by any set-off, counterclaim,
recoupment, defense or other claim, right or action that the Company may have
against Executive or others; and (d) be subject to any requirement that
Executive seek other employment or take any other action by way of mitigation,
nor will it be offset or otherwise be reduced by

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reason of Executive's receipt of compensation from any source other than the
Company.

6. Non-exclusivity of Rights. Nothing in this Agreement shall prevent or limit
Executive's continuing or future participation in any benefit, bonus, incentive
or other plans, programs, policies or practices provided by the Company or any
of its affiliated companies and for which Executive may qualify, nor shall
anything herein limit or otherwise affect such rights as Executive may have
under any other agreements with the Company or any of its affiliated companies.
Amounts that are vested benefits or that Executive is otherwise entitled to
receive under any plan, policy, practice or program of the Company or any of its
affiliated companies at or subsequent to the Date of Termination shall be
payable in accordance with such plan, policy, practice or program. In addition,
nothing in this Agreement is intended to or should be construed to contradict,
modify or alter the terms and conditions of that certain offer letter entered
into by Executive and the Company on April 24, 2001 (the "Relocation Letter").
The terms and conditions of Executive's employment shall continue to be governed
by the Relocation Letter except as expressly set forth herein.

7. Legal Fees. The Company agrees to pay, to the full extent permitted by law,
all legal fees and expenses that Executive may reasonably incur, including the
costs and expenses of any arbitration proceeding, as a result of any contest
(regardless of the outcome thereof) by the Company or others of the validity or
enforceability of, or liability under, any provision of this Agreement or any
guarantee of performance thereof (including as a result of any contest by
Executive about the amount of any payment pursuant to this Agreement), plus in
each case interest on any delayed payment at the applicable Federal rate
provided for in Section 7872(f)(2) of the Internal Revenue Code of 1986, as
amended (the "Code"); provided that Executive's claim is not determined by a
court of competent jurisdiction or an arbitrator to be frivolous or otherwise
entirely without merit.

8. Termination of Original CIC Agreement; Release.

        a. Termination of Original CIC Agreement. This Agreement terminates all
rights and obligations of the Company and Executive under the Original CIC
Agreement and supersedes any previous agreement between the Company and
Executive, written or oral, to the extent such agreement relates to the subject
matter hereof.

        b. General Release of All Claims.

               i. Executive fully and unconditionally releases and discharges
all claims and causes of action that Executive or Executive's heirs, personal
representatives, successors, or assigns ever had, now have, or hereafter may
have against the Company, and any subsidiary corporations, divisions and
affiliated corporations, partnerships or other affiliated entities of the
Company, past and present, as well as the Company's employees, officers,
directors, agents, shareholders, successors and assigns (collectively, "Released
Parties") on account of any claims and/or causes of action arising out of or
relating to the Original CIC Agreement and any other document relating thereto
or delivered in connection with the transactions contemplated thereby.

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<PAGE>

               ii. Executive declares and represents that Executive intends this
Agreement to be complete and not subject to any claim of mistake, and that the
release herein expresses a full and complete release of all claims, known and
unknown, suspected or unsuspected arising out of or relating to the Original CIC
Agreement and any other document relating thereto or delivered in connection
with the transactions contemplated thereby and, regardless of the adequacy or
inadequacy of the consideration, Executive intends the release herein to be
final and complete. Executive executes this Agreement with the full knowledge
that the release covers all possible claims against the Released Parties arising
out of or relating to the Original CIC Agreement, to the fullest extent
permitted by law. Executive further agrees that this release is to be
interpreted broadly and includes the waiver of all rights under California Civil
Code section 1542, which provides that "a general release does not extend to
claims which the creditor does not know or suspect to exist in his favor at the
time of executing the release, which if known by him must have materially
affected his settlement with the debtor."

9. Termination of Settlement and Retention Agreement; Release. Simultaneous with
the payment of the last installment of the Settlement Payment, Executive agrees
to sign a release similar to the release set forth in Section 8(b) above that
acknowledges that the Company has fully performed and satisfied all of its
obligations under this Agreement and that releases all claims or causes of
action arising out of or relating to this Agreement.

10. Arbitration. Any dispute, controversy or claim arising out of or relating to
this Agreement, or any breach thereof, shall be determined and settled by
arbitration to be held in the City of San Diego pursuant to the employment rules
of the American Arbitration Association or any successor organization. Any award
rendered there under shall be final, conclusive and binding on the parties.

11. Successors.

        a. This Agreement is personal to Executive and without the prior written
consent of the Company shall not be assignable by Executive otherwise than by
will or the laws of descent and distribution. This Agreement shall inure to the
benefit of and be enforceable by Executive's legal representatives.

        b. This Agreement shall inure to the benefit of and be binding upon the
Company and its successors and assigns.

        c. The Company will require any successor (whether direct or indirect,
by purchase, merger, consolidation or otherwise) to all or substantially all of
the business and/or assets of the Company to assume expressly and agree to
perform this Agreement in the same manner and to the same extent that the
Company would be required to perform it if no such succession had taken place.
As used in this Agreement, "Company" shall mean the Company as herein defined
and any successor to its business and/or assets as aforesaid that assumes and
agrees to perform this Agreement by operation of law, or otherwise.

12. New CIC Agreement. The parties agree to enter into a new Change in Control
Agreement contemporaneously with the execution of this Agreement, which shall be
in the standard form of such agreement adopted by the Board of Directors of
Invitrogen (the "New CIC Agreement").

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<PAGE>

13. General Provisions.

        a. Governing Law. This Agreement shall be governed by and construed in
accordance with the laws of the State of California, without reference to
principles of conflict of laws. The captions of this Agreement are not part of
the provisions hereof and shall have no force or effect. This Agreement may not
be amended or modified otherwise than by a written agreement executed by the
parties hereto or their respective successors and legal representatives.

        b. Notices. All notices and other communications hereunder shall be in
writing and shall be given by hand delivery to the other party or by registered
or certified mail, return receipt requested, postage prepaid, to the addresses
set forth below or to such other address as either party shall have furnished to
the other in writing in accordance herewith. Notice and communications shall be
effective when actually received by the addressee.

        c. Severability. The invalidity or unenforceability of any provision of
this Agreement shall not affect the validity or enforceability of any other
provision of this Agreement.

        d. Waiver. Either party's failure to insist upon strict compliance with
any provision hereof in any particular instance shall not be deemed to be a
waiver of such provision or any other provision thereof.

        e. Counterparts. This Agreement may be signed in two counterparts, each
of which together shall constitute one and the same Agreement, binding on the
parties as if each had signed the same document.

IN WITNESS WHEREOF, the parties have caused this Agreement to be executed as of
the date first written above.

INVITROGEN CORPORATION                       John A. Cottingham

By: /s/                                      /s/
   --------------------------------          -----------------------------------
Printed Name: L. James Runchey               7955 Sitio Solana
                                             Carlsbad, CA  92009
Title: VP, Human Resources

Address:       Invitrogen Corporation
               1600 Faraday Avenue
               Carlsbad, CA 92008
               (ATTN:  General Counsel)

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