AMENDED AND RESTATED STOCK PURCHASE AND SALE AGREEMENT

EXHIBIT 10.1

For further information contact:

Dr Paul D’Sylva

CEO

Commonwealth Biotechnologies, Inc.

858 699 0298

Dr. John P McAlister

CEO

Tripos, Inc.

314 616.4473

AMENDED AND RESTATED STOCK PURCHASE AND SALE AGREEMENT

by and among

Tripos, Inc.,

a Utah corporation,

Tripos UK Holdings Limited,

a private limited company incorporated in England,

and

Commonwealth Biotechnologies, Inc.,

a Virginia corporation

Dated as of June 6, 2007

TABLE OF CONTENTS

i

ii

AMENDED AND RESTATED STOCK PURCHASE AND SALE AGREEMENT

THIS AMENDED AND RESTATED STOCK PURCHASE AND SALE AGREEMENT (this “Agreement”), made and entered into this 6 ^th day of June, 2007, by and among Tripos, Inc., a Utah corporation (“Parent”), Tripos UK Holdings Limited, a wholly-owned subsidiary of Parent and a private limited company incorporated in England (“Seller”), and, Commonwealth Biotechnologies, Inc., a Virginia corporation (“Purchaser”).

RECITALS

1. Seller is the owner of a discovery research business (the “Business”) conducted through the operation of its wholly-owned subsidiary Tripos Discovery Research Ltd. (“TDR”);

2. Purchaser desires to purchase from Seller, and Seller desires to sell to Purchaser, all of the issued and outstanding share capital of TDR comprising 101,000 shares of £1.00 each (the “Acquired Shares”), which transfer shall cause the Purchaser to own one hundred percent (100%) of TDR, all for the purchase price and subject to the terms and conditions set forth in this Agreement; and

3. On May 11, 2007, Seller and Purchaser entered into a Stock Purchase and Sale Agreement.

4. On May 12, 2007, Purchaser remitted to Seller $350,000 as a non-refundable deposit for the purchase price hereunder.

NOW, THEREFORE, in consideration of the premises and the representations, warranties, covenants and agreements contained herein, the receipt and sufficiency of which are hereby acknowledged, the parties hereto, intending to be legally bound, hereby agree as follows:

ARTICLE 1

PURCHASE AND SALE OF SHARES

1.1. Sale and Delivery of Shares . Subject to the terms and conditions hereof, Seller agrees to sell, assign, transfer and deliver, or cause to be sold, assigned, transferred and delivered, to Purchaser, and Purchaser agrees to purchase and accept from Seller at the “Closing” (as hereinafter defined), all of Seller’s right, title and interest in and to the Acquired Shares for the Purchase Price (as defined in Article 2 hereof).

ARTICLE 2

PURCHASE PRICE

2.1. Payment of Purchase Price. The total consideration for the Acquired Shares (the “Purchase Price”) shall be three hundred fifty thousand dollars US ($350,000.00) (the “Consideration”). Purchaser delivered to the Seller the Purchase Price on May 12, 2007.

ARTICLE 3

REPRESENTATIONS AND WARRANTIES OF SELLER

Except as set forth in the Seller disclosure schedule attached to this Agreement (the “Seller Disclosure Schedule”) (with respect to which any particular reference to a section or subsection of this Agreement shall be deemed to be disclosed under all other sections or subsections of this Agreement), each of the Seller and Parent hereby represents and warrants to Purchaser that:

3.2 Organization, Good Standing and Qualification. Parent is a corporation duly organized, validly existing and in good standing under the laws of the State of Utah, and each of Seller and TDR is a limited company duly incorporated and validly existing under the laws of England and Wales. Seller and TDR each has all requisite corporate or similar power and authority to own and operate its properties and assets and to carry on its business as presently conducted and is qualified to do business in each jurisdiction where the ownership or operation of its properties or conduct of its business requires such qualification.

3.3 Capitalization. The Acquired Shares constitute the entire allotted and issued share capital of TDR and are fully paid or credited as fully paid. Seller is the sole legal and beneficial owner of the entire allotted and issued share capital of TDR. The issued shares of TDR are fully paid up and, free from Encumbrances. There are no preemptive or other outstanding rights, options, warrants, conversion rights, redemption rights or repurchase rights to issue or sell any shares of TDR or any securities or obligations convertible or exchangeable into or exercisable for, or giving any Person a right to subscribe for or acquire, any securities of TDR.

3.4 Corporate Authority and Approvals. Each of Parent and Seller has the necessary corporate power and authority and has taken all corporate action necessary in order to execute, deliver and perform its obligations under this Agreement and to carry out and complete the sale of the Acquired Shares. The execution and delivery of this Agreement by Parent and Seller and the consummation by Parent and Seller of the transactions contemplated hereby have been duly and validly authorized by all necessary corporate action and no other corporate proceedings on the part of Parent or Seller are necessary to authorize this Agreement or to consummate the transactions contemplated hereby to the extent required under the UBCA or the laws of England or Wales. This Agreement has been duly executed and delivered by both Parent and Seller and, assuming the due authorization, execution and delivery by Purchaser, constitutes a legal, valid and binding obligation of both Parent and Seller, enforceable against Parent and Seller in accordance with its terms, except as such enforceability may be limited in either case by

2

bankruptcy, insolvency, reorganization, moratorium and other similar laws of general applicability relating to or affecting creditors’ rights generally and by the application of general principles of equity (regardless of whether enforcement is sought in a proceeding at law or in equity).

3.5 Title to Shares and Assets. The Seller has marketable title to the Acquired Shares free and clear of all Encumbrances. Except as set forth in Section 3.4 of the Seller Disclosure Schedule, and except for capital leases or security to Parent for advances made to TDR, Seller has marketable title to all of the assets of the Business, free and clear of all Encumbrances, except liens for taxes not yet due and payable.

3.6 Government Filings; No Violations or Conflicts. Except as set forth in Section 3.5 of the Seller Disclosure Schedule, the execution and delivery of this Agreement by Parent and Seller do not, and the performance by Parent and Seller of their respective obligations under this Agreement will not, (i) conflict with or violate the organizational documents of Parent, Seller, or TDR, or (ii) conflict with or violate any law, statute, ordinance, rule, regulation, order, judgment or decree applicable to Parent, Seller or TDR.

3.7 Litigation. No suit, proceeding, hearing or governmental investigation is pending or, to the knowledge of Seller, threatened in writing against Seller or TDR.

3.8 Brokers. Neither Parent, Seller nor any of their executive officers, directors or employees has employed any broker or finder or incurred any liability for any brokerage fees, commissions or finders fees in connection with the transactions contemplated by this Agreement, except that for any agreement with Seven Hills Partners LLC for financial advisory services rendered to Parent at sole expense of Parent.

3.9 Compliance with Laws, Permits. TDR holds all permits, licenses and approvals (none of which has been modified or rescinded and all of which are in full force and effect) from all necessary for TDR to carry on the Business as presently conducted (collectively, the “ Permits ”). The Business is not being conducted in material violation of any applicable law, statute, ordinance, regulation, judgment, Permit, order, decree, concession, grant or other authorization of any Governmental Entity.

3.10 Environmental Matters.

(1) “Dangerous Substance” means any natural or artificial substance (whether solid, liquid or gas and whether alone or in combination with any other substance or radiation) capable of causing harm to any human or other living organism or damaging the Environment, public health or welfare.

(2) “Environment” means the environmental media of air, water and land, all living organisms and natural or man-made structures.

3

(3) “Environmental Law” means all law in England and Wales relating to the protection of human health or the Environment, the conditions of the workplace or the generation, transportation, storage, treatment, emission or disposal of a Dangerous Substance or Waste.

(4) “Environmental License” means any authorization, license, consent or permission required under any Environmental Law.

(5) “Waste” means any unwanted or surplus substance irrespective of whether it is capable of being recycled or recovered or has any value.

(b) TDR has at all times complied in all material respects with Environmental Law and obtained, and complied with, all Environmental Licenses necessary for carrying on the Business and is not in material breach of any Environmental Law.

(c) The Environmental Licenses necessary for carrying on the Business are in full force and effect and there are no circumstances existing which will give rise to the suspension or revocation of, to lead to the imposition of unusual or onerous conditions on, or to prejudice the renewal of, any of those licenses.

3.11 Labor Matters.

(a) Seller has made available to Purchaser copies of all standard form contracts and handbooks and policies which apply to the employees, officers and directors of TDR.

(b) There is no outstanding claim against TDR by any Person who is now or has been an employee or officer of TDR.

(c) TDR is not party to any collective bargaining agreement with any trade union or staff association other than as required by government regulation.

(d) TDR has not formally recognized a trade union and is not a party to any agreement with any trade union or group or organization representing employees in respect of its employees.

(e) TDR has not in the last six (6) years provided, or agreed to provide, any loan, gratuitous payment or gratuitous benefit to any of its directors, officers or employees or any of their dependants which remains outstanding.

3.12 Intellectual Property.

(a) For purposes of this Section 3.11, “Business Intellectual Property” means all of the: (i) patents and patent applications; (ii) registered trademarks and trademark applications and material unregistered trademarks; (iii) copyrights; and (iv) registered domain names owned by TDR and used in the Business.

4

(b) The registrations in connection with the Business Intellectual Property are valid and subsisting, all necessary registration and renewal fees in connection with such registrations have been paid, and all necessary documents and certificates in connection with such registrations have been filed with the relevant authorities for the purposes of maintaining such registrations.

(c) There are no contracts, licenses and agreements between Parent, Seller or TDR, on the one hand, and any other Person, on the other hand, relating primarily to the Business Intellectual Property as to which there is any dispute regarding the scope of such agreement, or performance under such agreement including with respect to any payments to be made or received by TDR thereunder.

(d) Neither Parent, Seller or TDR has received notice from any Person that the operation of the Business, including the design, development, manufacture and sale of products and provision of services infringes the intellectual property of any Person.

(e) To the knowledge of Parent and Seller, no Person is materially infringing any of the Business Intellectual Property.

ARTICLE 4

REPRESENTATIONS AND WARRANTIES OF PURCHASER

Purchaser hereby represents and warrants to Seller as follows:

4.1 Organization and Authority.

(a) Purchaser is a corporation duly incorporated, validly existing and in good standing under the laws of the Commonwealth of Virginia. Purchaser has all requisite corporate power and authority to execute and deliver this Agreement and perform its obligations hereunder.

(b) The execution and delivery of this Agreement by Purchaser and the performance of its obligations hereunder, have been duly authorized by all necessary corporate action on the part of Purchaser. This Agreement has been duly executed and delivered by Purchaser and constitutes a valid and binding obligation of Purchaser, enforceable against Purchaser in accordance with its terms, except as such enforceability may be limited by bankruptcy, insolvency, reorganization, moratorium and other similar laws of general applicability relating to or affecting creditors’ rights generally and by the application of general p