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Exhibit 10.55
 First Amendment to Lease Agreement
 Amendment Effective Date Landlord Tenant
  A.
    
    Aetna Life Insurance Company, Landlords predecessor-in-interest, and Tenant entered
into that certain Lease Agreement, dated as of May 26, 2000 (the Lease), which Lease
covers certain premises containing approximately Sixty Thousand Sixty-One (60,061)
rentable square feet, located at 1311 Orleans Drive, Sunnyvale, California (the
Premises).
 B.
    
    Landlord and Tenant now desire to amend the Lease to modify the Monthly Base Rent
schedule and extend the Term, subject to each of the terms, conditions, and provisions set
forth herein. Capitalized terms used but not defined herein shall have the meanings
ascribed to them in the Lease.
   1.
    
    RECITALSLandlord and Tenant agree the above recitals are true and correct and are hereby
incorporated herein as though set forth in full.2.
    
    EXTENDED TERMThe Term of the Lease is hereby extended by a term of approximately sixty-four months, and
the Expiration Date is hereby modified to be February 28, 2013.3.
    
    OPTION TO RENEWThe first sentence of Paragraph 48 of the Lease is hereby modified to read as follows:
The Tenant shall have one (1) option (the Renewal Option) to extend the Term for a
period of three (3) years beyond the Expiration date (the Renewal Term). The Renewal
Option is personal to Tenant and may not be exercised by any sublessee or assignee, or by
any other successor or assign of Tenant.4.
    
    BASE RENTThe Monthly Base Rent payable by Tenant to Landlord, in accordance with Paragraph 4 of the
Lease, is hereby modified to be payable in accordance with the following schedule:
 Monthly Base Rent
    
    Period
    
    Sq.Ft.
    
    Monthly Base Rate
    
    Monthly Base Rent3/1/06-2/28/07
    
    
    60,061
    
    
    x $2.18
    
    =$130,932.983/1/07-2/29/08
    
    
    60,061
    
    
    x $2.24
    
    =$134,536.643/1/08-2/28/09
    
    
    60,061
    
    
    x $2.31
    
    =$138,740.913/1/09-2/28/10
    
    
    60,061
    
    
    x $2.38
    
    =$142,945.183/1/10-2/28/11
    
    
    60.061
    
    
    x $2.45
    
    =$147,149.453/1/11-2/28/12
    
    
    60,061
    
    
    x $2.53
    
    =$151,954.333/1/12-2/28/13
    
    
    60,061
    
    
    x $2.60
    
    =$156,158.60




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5.
    
    REFURBISHMENT ALLOWANCETenant accepts the Premises as suitable for Tenants intended use and as being in good and
sanitary operating order, condition, use or occupancy which may be made thereof and
without any improvements or alterations by Landlord. Landlord agrees to contribute an
amount not to exceed $3.00 per square ($180,183.00) (Landlords Contribution) toward the
cost of any Alterations made to the Premises to refurbish the same (Tenants
Refurbishment Work). Landlord shall pay Landlords Contribution to Tenant as
reimbursement for actual and reasonable costs incurred by Tenant in performing Tenants
Refurbishment Work within thirty (30) days following the later to occur of (i) Landlords
receipt of a Certificate of Occupancy for the Premises, if such is required in connection
with Tenants Refurbishment Work; (ii) Landlords receipt of a certificate from Tenants
licensed contractor certifying completion of Tenants Refurbishment Work in accordance
with the construction plans and specifications therefore, which plans and specifications
have previously been approved by Landlord; (iii) Landlords receipt of documentary
evidence reasonably satisfactory to Landlord of all of Tenants expenditures for work
performed and materials used in completing Tenants Refurbishment Work; and (iv)
Landlords receipt of final, unconditional lien releases in form and content satisfactory
to Landlord from all persons or entities providing labor and/or materials in connection
with Tenants Refurbishment Work. Notwithstanding anything herein to the contrary, if any
portion of the Landlords Contribution remains unused by Tenant as on March 1, 2007, then
Landlord shall have no further obligation to reimburse Tenant for any costs of Tenants
Refurbishment Work and any such unused portion of Landlords Contribution shall belong to
Landlord. If the cost of Tenants Refurbishment Work exceeds Landlords Contribution, then
such excess amount shall be borne solely by Tenant.6.
    
    GENERAL PROVISIONS
 (a)
    
    Ratification and Entire Agreement.Except as expressly amended by
this Amendment, the Lease shall remain unmodified and in full force and effect. As
modified by this Amendment, the Lease is hereby ratified and confirmed in all
respects. In the event of any inconsistencies between the terms of this Amendment
and the Lease, the terms of this Amendment shall prevail. The Lease as mended by
this Amendment constitutes the entire understanding and agreement of Landlord and
Tenant with respect to the subject matter hereof, and all prior agreements,
representations, and understandings between Landlord and Tenant with respect to
the subject matter hereof, whether oral or written, are or should be deemed to be
null and void, all of the foregoing having been merged into this Amendment.
Landlord and Tenant do each hereby acknowledge that it and/or its counsel have
reviewed and revised this Amendment, and agree that no rule of construction to the
effect that any ambiguities are to be resolved against the drafting party shall be
employed in the interpretation of this Amendment. This Amendment may be amended or
modified only by an instrument in writing signed by each of the Landlord and
Tenant.(b)
    
    Brokerage.Tenant hereby represents and warrants to Landlord that it
has not retained the services of any real estate broker, finder or any other
person whose services would for the basis for any claim for any commission or fee
in connection with this Amendment or the transactions contemplated hereby, other
than Cresa Partners. Tenant hereby agrees to save, defend, indemnify and hold
Landlord free and harmless from all losses, liabilities, damages, and costs and
expenses arising from any breach of its warranty and representation as set forth
in the preceding sentence, including Landlords reasonable attorneys fees.(c)
    
    Authority; Applicable Law; Successors Bound.Landlord and Tenant do
each hereby represent and warrant to the other that this Amendment has been duly
authorized by all necessary action on the part of such party and that such party
has full power and authority to execute, deliver and perform its obligations under
this Amendment. This Amendment shall be governed by and construed under the laws
of the State of California, without giving effect to any principles of conflicts
of law that would result in the application of the laws of any other jurisdiction.
This Amendment shall inure to the benefit of and be




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binding upon Landlord and Tenant and their respective successors and permitted
assigns with respect to the Lease.(d)
    
    Counterparts.This Amendment may be executed in counterparts each of
which shall be deemed an original but all of which taken together shall constitute
one and the same instrument.
  LANDLORD:
    
    MOFFET OFFICE PARK INVESTORS LLC,A Delaware limited liability companyBy: UBS Realty Investors LLC,A Massachusetts limited liability company,
Its ManagerBy:/s/ Thomas EngerThomas EngerDirectorTENANT:
    
    MOLECULAR DEVICES CORPORATION,A California CorporationBy:/s/ Tim HarknessTim HarknessChief Financial Officer and Senior Vice President Finance and OperationsBy:/s/ Patricia SharpPatricia Sharp
      Vice President Human ResourcesIn Conformance with California
Corporations Code §313,this document is to
be signed by (i) the Chairman of theBoard,
the president or any vice president,
and (ii)the secretary, any
assistant secretary, the chief financial
officer, or any assistant treasurer of the
Tenant.