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                                                                    Exhibit 4.10

                           MANAGING DIRECTOR AGREEMENT


                                 by and between


           DIAGEN Institute for Molecular Biological Diagnostics GmbH,
                        Eichenwand 15, 4000 Dusseldorf 12
                      Represented by the Board of Directors

                        - hereinafter DIAGEN or Company-

                                       and

                                Dr. Metin Colpan


                        - hereinafter Managing Director -

The following managing director agreement is concluded between the parties
effective July 7, 1985:

                                    Article 1
                           Function and Authorization

(1)  Dr. Colpan shall assume the responsibility of Managing Director based on
     the November 29, 1984 resolution. The rights and obligations of Dr. Colpan
     as Managing Director of DIAGEN are determined in accordance with this
     agreement by the company agreement, supplementary legal regulations and
     company rules and regulations.

     (2)  Dr. Colpan shall represent the company in cooperation with another
          Managing Director or Proxy. He is, to the extent simultaneously a
          Partner and Managing Director, released form the restrictions of
          self-dealing according to (S) 181 BGB.

     (3)  Dr. Colpan is obligated to follow the instructions of the
          Shareholders' Meeting and Board of Directors. This applies to general
          regulations with regard to managing the company as well as to the
          Company Rules and Regulations which indicates the boundaries of
          management authority and responsibility as well as the list of

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     activities needing the approval provided in the latest effective version of
     the Shareholder Agreement including any prospective changes to it.

                                    Article 2
                         Job Description and Management

(1)  The activities incumbent upon Dr. Colpan shall be those assigned by
     organizational chart according to resolution of the Board of Directors. He
     performs his responsibilities in cooperation with another Managing
     Director. This applies especially in the case of such business which must
     be submitted to all of the Directors for approval in accordance with the
     Company Rules and Regulations.

(2)  Dr. Colpan shall manage the company with the care and prudence of an
     ordinary business man and perform the tasks assigned to him during his
     activities conscientiously and to the best of his abilities, to safeguard
     and promote the employer's interests in every respect and to dedicate all
     his activities and their consequences to exclusively to DIAGEN, to the
     extent not expressly determined otherwise by the company. Ancillary
     employment - also advisory, expert or of a similar nature -, such as the
     acceptance of positions on advisory committees, supervisory boards, boards
     of directors, chambers of commerce and other committee associations, etc.,
     shall only be permissible if express prior consent may be obtained from the
     Supervisory Board.

(3)  Dr. Colpan shall inform his Co-Managing Director and the Supervisory Board,
     if necessary, about all activities which may be of interest. The above
     applies also to observations and information outside of his own direct area
     of responsibility.

                                    Article 3
                           Trade and Business Secrets

(1)  Dr. Colpan is obligated to maintain total and absolute secrecy on all
     confidential matters and activities, in particular on business and
     operational secrets, that he obtains knowledge of within the framework of
     his activities during his employment as well as after his leaving the
     employment relationship including knowledge of program systems, company and
     operating equipment and procedures, production and sales figures for the
     group of associated companies, especially with respect to customer lists,
     marketing plans, business documents, sketches, specifications, methods,
     process techniques, business practices, formulas, business, personal and
     financial data, data base, product/ processing specifications and drawings,
     test ledgers and instructions, internal reports, planned research
     initiatives, recycling plans, public funding, and all other documents and
     information related to the conditions of the company, associated companies
     and persons, business partners, employees and similar persons. The secrecy
     obligation shall also apply to physical objects, especially designs, and
     includes the obligation not to publish or share such information and
     prevent the publishing or sharing of such information by other persons. The
     obligations shall not be applicable to the extent that such information

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     has been or shall be published without the knowledge and consent of Dr.
     Colpan or to the extent that exchange of information or materials with
     third parties seems well understood to be in the interest of the company.
     The obligation of secrecy extend beyond the parameters of the contractual
     relationship. It is applicable not only in relationship to any external
     third parties but also DIAGEN employees and subcontractors to the extent
     the latter are not unquestionably authorized to receive such information by
     way of their official activities.

(2)  The special regulations defining penalties for violation of business and
     trade secrets according to (S)17 of the law against unfair competition are
     familiar to Dr. Colpan.

                                    Article 4
                   Operating Results and Creative Developments

(1)  Rights to inventions or other technical improvements which Dr. Colpan
     develops or acquires during his employment as Managing Director of the
     company or in connection with his activities for the company belong to the
     company. Dr. Colpan shall with this agreement assign all corresponding
     rights to DIAGEN.

(2)  The company is in this regard not obligated to provide any additional
     compensation. The law on employer rights in employee inventions is not
     applicable since Dr. Colpan's activities do not fall within the definitions
     of employee.

(3)  Dr. Colpan shall assign DIAGEN the exclusive use of all patented rights in
     his possession whether in connection with his current activities, based on
     his prior experience and employment with the company or produced by the
     company itself.

(4)  Dr. Colpan is obligated to offer DIAGEN the use of any inventions or
     technical improvements he has developed not included in the Article 1
     description. If DIAGEN chooses to use these inventions or technical
     improvements, Dr. Colpan shall receive appropriate compensation.

(5)  Dr. Colpan promises to keep the company informed of details in connection
     with inventions, technical improvements, and gained independent know-how
     with regard to the meaning of patentable and non-patentable inventions
     improvements, etc., for example, knowledge obtained through conversations
     with experts.

                                    Article 5
                             Anti-Competition Clause

(1)  For the duration of this agreement, Dr. Colpan is not permitted to engage
     in activities for a company resembling the DIAGEN Group or which could
     potentially compete with the DIAGEN Group either on his own or for a
     third-party, independently or dependently. This prohibition applies to any
     activity including advising or promoting such a company in another way,
     notwithstanding whether the activity is performed temporarily or only
     occasionally.

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This above described anti-competition clause applies in Germany and extends
beyond the termination of the contractual relationship for a period of one year.
To the extent the effectiveness of competing offers shall be dependent on
payment of compensation, DIAGEN promises to pay the legally defined minimum
compensation according to legal regulations and jurisdictional principles. Dr.
Colpan is, in the case of mandatory compensation, obligated to communicate
information relating to which company he is engaged by and the amount of
compensation received. DIAGEN shall be permitted to withdraw this
post-contractual anti-competition clause at any time prior to the ending of this
agreement in writing.

                                    Article 6
                                  Compensation

(1)  Dr. Colpan shall be compensated for his activities by a fixed annual gross
     amount of DM 104,000.-- payable in accordance with legally prescribed
     deductions in 12 monthly equal amounts of DM 8,000.-- retroactively at the
     end of every month and a 13th salary in the amount of DM 8,000.--with the
     November salary. In addition to the annual gross salary, Dr. Colpan shall
     receive holiday pay in the amount of 25% of the gross monthly salary
     consequently at the moment DM 2,000.--.

(2)  Furthermore, Dr. Colpan shall be entitled to receive an appropriate,
     results-contingent share of profits, the amount of which shall be
     recommended by the Board of Directors during its approval of the annual
     report. The bonus shall be received within two weeks of Board Approval.

(3)  According to the provisions on compensation according to Articles 6.1 and
     6.2, the entire Managing Director activity by Dr. Colpan including
     responsibility for subsidiaries, participating investments or other
     companies. To the extent that Dr. Colpan receives direct compensation for
     such mandate from the companies concerned, shall this compensation be
     treated in accordance with this agreement and charged to the bonus to the
     extent not agreed otherwise.

(4)  If Dr. Colpan is prevented from performing his duties because of disability
     due to illness or accident that is not his fault, he shall not lose his
     claim to fixed compensation for the period of his inability to work up to
     the end of the sixth full month following the onset of his inability to
     work. Third party payments such as shall be received from liability claims,
     health insurance, etc. shall be used by the company to make up the net
     salary Dr. Colpan would have received should he have been able to work.

                                    Article 7
                      Other Compensation and Reimbursement

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(1)  The Employee will be provided with a midrange business vehicle which he may
     also use for private use. The monetary value of private vehicle use subject
     to income tax in conformity with tax regulations and chargeable to the
     Employee is taken into account in the payment of remuneration indicated in
     Article 6.1.

(2)  DIAGEN shall include Dr. Colpan in the existing group accident insurance
     which cover all risks of accidents, also those apart from the workplace.
     The insurance amount in the event of death shall be DM 50,000.00, in the
     event of disability, DM 200,000.00. Beneficiary from the insurance shall be
     Dr. Colpan or the person he designates. The insurance premium shall be
     treated as compensation according to 6.1 above and so allocated.

(3)  Lodging and travel expenses including the costs of overnight stays and
     other expenditures in the interests of the company shall be reimbursed to
     Dr. Colpan within appropriate limits. Guidelines for reimbursement claims
     shall be explicitly followed in the case that expenditures related to
     publicly subsidized projects. The expenditures shall be individually
     documented according to tax requirements to the extent not deducted as a
     lump sum for tax purposes.

                                    Article 8
                                    Vacation

(1)  Dr. Colpan shall be entitled to an annual vacation of 25 workdays.

(2)  Vacation date shall be determined in consultation with the Co-Managing
     Director, if needed with the assistance of the Chairman of the Board of
     Directors, demonstrating appropriate consideration for the functional
     concerns of the company.

(3)  Any vacation not taken shall be forfeited on March 31 of the subsequent
     year. A claim for compensation may not be rendered legal enforceable on
     fundamental grounds.

                                    Article 9
              Duration and Termination of the Employment Agreement

(1)  The employment agreement is concluded for an indeterminate time period and
     enters into effect on July 1, 1985.

(2)  The employment agreement may be terminated by either party at the end of
     each calendar half-year, with six months notice, at the earliest, however,
     June 30, 1990. In cases of doubt, termination as Managing Director serves
     simultaneously as termination of the Managing Director Agreement at the
     next possible date. Termination shall be communicated by registered letter.
     The company shall be represented by the Board of Directors in the case of
     termination notwithstanding which party has initiated the request unless
     not legally permissible.

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(3)  The right to terminate this agreement for serious cause shall remain
     unaffected. An important reason for the company is represented by violation
     of essential provisions of the agreement or of restrictions imposed on
     inner relations or if the Managing Director leaves prior to March 31, 1990.

(4)  The employment relationship shall end without notice at the expiration of
     the month in which Dr. Colpan reaches age 65, or in case of a prolonged
     inability to work which shall be conclusively determined through medical
     evaluation performed by a doctor which the company selects.

                                   Article 10
                                   Termination

(1)  In the case of termination of the contractual relationship, Dr. Colpan
     shall be released from his responsibilities under the terms of this
     agreement independent of the effectiveness of the termination subject to
     the satisfying of other commitments and his legal rights.

(2)  At the time of termination of the agreement, in the case of release at this
     date, Dr. Colpan shall return business and personal documents related to
     operating procedures of DIAGEN or associated companies, other materials
     including photocopies, duplicates, extracts, as well as any other types of
     copies or recorded information without needing to be requested by the
     company; all documents related to the company no matter what format remain
     sole possession of the company. With regard to a business vehicle provided
     by the company, at any time between notice of termination and expiration of
     the agreement, the company may decide upon return of the vehicle with
     appropriate financial remuneration to be made to compensate the loss of
     private vehicle use.

(3)  At the request of the company, as soon as notice of termination has been
     communicated, Dr. Colpan is obligated to cease all mandates for which he is
     responsible in his capacity as Managing Director or in connection with this
     post irrespective of which party has submitted the request for termination
     of the employment relationship.

(4)  Dr. Colpan expressly promises to undertake neither direct nor indirect
     patent registration without offering the company use of the respective
     discovery for the duration of the employment agreement through its
     termination. The company promises on its part to maintain strict
     confidentiality with regard to any communication from Dr. Colpan about such
     a discovery, to indemnify Dr. Colpan against any damages, particularly in
     the event that DIAGEN does not use the discovery, and in the event of use,
     to grant compensation the amount of which shall be dependent upon in what
     measure the discovery has been based on the preceding activity of DIAGEN.

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                                   Article 11
                               Contractual Penalty

     A serious violation of the agreement by Dr. Colpan, especially against the
     obligations of secrecy, anti-competition clause, requirement to return all
     documents by termination of the agreement or the promise to communicate the
     news of inventions and offer use, etc., also after termination of this
     agreement, Dr. Colpan shall have to pay a contractual penalty in the amount
     of one quarter of his annual salary. The contractual penalty shall be
     incurred at each case of violation. Payment of this penalty is due
     immediately exclusive of any offset, retention or denial of services on the
     part of the Managing Director.

(2)  The right to assert further damages in the case that penalties have not
     fully reflected damages incurred by the company or shareholders remains
     unaffected.

                                   Article 12
                                Final Provisions

(1)  This agreement contains all agreements between the parties. The parties
     have concluded no other agreements with the exception of the ones set forth
     above. Any amendments to the agreement shall be in writing.

(2)  Dr. Colpan declares that he is aware of no grounds for which this agreement
     shall not be concluded.

(3)  Place of performance and legal court of jurisdiction in any dispute arising
     from this agreements shall be that of the corporate headquarters. To the
     extent legally permissible, the court of arbitration agreement applies to
     any dispute concluded between the company and all shareholders in
     connection with this Managing Director Agreement

(4)  If any provision of this contract should be or become ineffective, the
     legal validity of the remaining provisions shall not be affected thereby.
     In lieu of the invalid provision, the parties agree to concur on a
     provision that comes the closest, in economic terms, to the invalid one.
     The same shall apply in the event of a loophole, or if any individual
     provisions should be or become impracticable.

Dusseldorf, August 30, 1985

DIAGEN Institute for Molecular Biological Diagnostics
For the Board of Directors:

By: /s/ D. Riesner
    ------------
Chairman of the Supervisory Board

Employee

/s/ Metin Colpan
----------------
Metin Colpan