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                                                                     EXHIBIT 4.1

                      FORM OF COMMON STOCK PURCHASE WARRANT

THIS SECURITY AND ANY SHARES ISSUED UPON EXERCISE OF THIS SECURITY HAVE NOT
BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE "ACT"), OR
APPLICABLE STATE SECURITIES LAWS AND MAY NOT BE TRANSFERRED OR OTHERWISE
DISPOSED OF UNLESS THE APPLICABLE SECURITY HAS BEEN REGISTERED UNDER THE ACT
AND SUCH LAWS OR (1) REGISTRATION UNDER SUCH LAWS IS NOT REQUIRED AND (2) AN
OPINION OF COUNSEL SATISFACTORY TO THE COMPANY IS FURNISHED TO THE COMPANY TO
THE EFFECT THAT REGISTRATION UNDER THE ACT AND THE APPLICABLE STATE
SECURITIES LAWS IS NOT REQUIRED.

                           ACACIA RESEARCH CORPORATION

WARRANT TO PURCHASE COMMON STOCK

       This certifies that, for value received,
________________________________ ("the Holder") is entitled to subscribe for
and purchase up to [_____________________] shares (subject to adjustment from
time to time pursuant to the provisions of Section 5 hereof) of fully paid
and nonassessable Common Stock of Acacia Research Corporation, a California
corporation (the "Company"), at the price specified in Section 2 hereof, as
such price may be adjusted from time to time pursuant to Section 5 hereof
(the "Warrant Price"), subject to the provisions and upon the terms and
conditions hereinafter set forth and callable by the Company upon the terms
and conditions set forth in Section 1 hereof.

       As used herein, the term "Common Stock" shall mean the Company's
presently authorized Common Stock, no par value, and any stock into or for
which such Common Stock may hereafter be converted or exchanged.

       This Warrant is issued pursuant to that certain Subscription Agreement
between the Holder and the Company dated December _____, 1999.

       l.     TERM OF WARRANT; CALLABILITY BY COMPANY.

       The purchase right represented by this Warrant is exercisable, in
whole or in part, at any time during a period beginning on the date hereof
and ending December 9, 2002. However, during the three-year period, the
Company will have the right to redeem all of the Warrants on 30 days prior
written notice at a redemption price of $0.10 per Warrant if (a) the closing
bid price of the Company's Common Stock averages $35.00 or above for 20
consecutive trading days after the Common Stock reaches a closing bid price
of at least $35.00 on the Nasdaq National Market System and (b) the
registration statement covering the resale of the shares of the Company's
Common Stock underlying this Warrant has been declared effective by the
Securities and Exchange Commission. If the Company elects to exercise its
redemption right, the Holder of this Warrant may either exercise the Warrant,
in whole or in part, or tender the Warrant to the Company for redemption, in
whole or in part. Within five business days after the end of the 30-day
period, the Company will mail a check for the redemption price to the Holder
of this Warrant should this Warrant remain outstanding in whole or in part as
of the end of the 30-day period, whether or not the Holder has surrendered
this Warrant for redemption. This Warrant may not be exercised after the end
of such 30-day period.

       2.     WARRANT PRICE

       The Warrant Price is $26.00 per share, subject to adjustment from time
to time pursuant to the provisions of Section 5 hereof.

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       3.     METHOD OF EXERCISE: PAYMENT; ISSUANCE OF NEW WARRANT.

       Subject to Section 1 hereof, the purchase right represented by this
Warrant may be exercised by the Holder, in whole or in part, by the surrender
of this Warrant (with the notice of exercise form attached hereto as Exhibit
1 duly executed) at the principal office of the Company and by the payment to
the Company, by cashier's check or wire transfer, of an amount equal to the
then applicable Warrant Price per share multiplied by the number of shares
then being purchased. The Company agrees that the shares so purchased shall
be deemed to be issued to the Holder as the record owner of such shares as of
the close of business on the date on which this Warrant shall have been
surrendered and payment made for such shares as aforesaid. In the event of
any exercise of the rights represented by this Warrant, certificates for the
shares of stock so purchased shall be delivered to the Holder within 15 days
thereafter and, unless this Warrant has been fully exercised or expired, a
new Warrant representing the portion of the shares, if any, with respect to
which this Warrant shall not then have been exercised, shall also be issued
to the Holder within such 15 day period.

       4.     STOCK FULLY PAID; RESERVATION OF SHARES.

       All Common Stock which may be issued upon the exercise of the rights
represented by this Warrant will, upon issuance, be fully paid and
nonassessable, and free from all taxes, liens and charges with respect to the
issue thereof. During the period within which the rights represented by this
Warrant may be exercised, the Company will at all times have authorized, and
reserved for the purpose of the issuance upon exercise of the purchase rights
evidenced by this Warrant, a sufficient number of shares of its Common Stock
to provide for the exercise of the rights represented by this Warrant.

       5.     ADJUSTMENT OF PURCHASE PRICE AND NUMBER OF SHARES.

       The kind of securities purchasable upon the exercise of this Warrant,
the Warrant Price and the number of shares purchasable upon exercise of this
Warrant shall be subject to adjustment from time to time upon the occurrence
of the following events:

              (a) RECLASSIFICATION, CONSOLIDATION, OR MERGER. In case of any
       reclassification or change of outstanding securities of the class
       issuable upon exercise of this Warrant (other than a change in par value,
       or from par value to no par value, or from no par value to par value, or
       as a result of a subdivision or combination), or in case of any
       consolidation or merger of the Company with or into another corporation,
       other than a merger with another corporation in which the Company is a
       continuing corporation and which does not result in any reclassification
       or change of outstanding securities issuable upon exercise of this
       Warrant, the Company, or such successor, as the case may be, shall
       execute a new Warrant, providing that the Holder of this Warrant shall
       have the right to exercise such new Warrant and procure upon such
       exercise, in lieu of each share of Common Stock theretofore issuable upon
       exercise of this Warrant, the kind and amount of shares of stock, other
       securities, money and property receivable upon such reclassification,
       change, consolidation, or merger by a Holder of one share of Common
       Stock. Such new Warrant shall provide for adjustments, which shall be as
       nearly equivalent as may be practicable to the adjustments provided for
       in this Section 5. The provisions of this subparagraph (a) shall
       similarly apply to successive reclassification, changes, consolidations,
       and mergers.

              (b) SUBDIVISION OR COMBINATION OF SHARES. If the Company at any
       time while this Warrant remains outstanding and unexpired shall subdivide
       or combine its common stock, or distribute dividends on its common stock
       payable in Common Stock, the Warrant Price shall be proportionately
       decreased in the case of a subdivision or increased in the case of a
       combination or dividend.

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              (c) ADJUSTMENT OF NUMBER OF SHARES. Upon each adjustment in the
       Warrant Price pursuant to any of subparagraphs (a) through (c) of this
       Section 5, the number of shares of Common Stock purchasable hereunder
       shall be adjusted, to the nearest whole share, to the product obtained by
       multiplying the number of shares purchasable immediately prior to such
       adjustment in the Warrant Price by a fraction, the numerator of which
       shall be the Warrant Price immediately prior to such adjustment and the
       denominator of which shall be the Warrant Price immediately thereafter.

       6.     NOTICE OF ADJUSTMENTS.

       Whenever any Warrant Price shall be adjusted pursuant to Section 5
hereof, the Company shall prepare a certificate signed by its chief financial
officer setting forth, in reasonable detail, the event requiring the
adjustment, the amount of the adjustment, the method by which such adjustment
was calculated, the Warrant Price after giving effect to such adjustment and
the number of shares then purchasable upon exercise of this Warrant, and
shall cause copies of such certificate to be mailed (by first class mail,
postage prepaid) to the Holder of this Warrant at the address specified in
Section 10(c) hereof, or at such other address as may be provided to the
Company in writing by the Holder of this Warrant.

       7.     FRACTIONAL SHARES.

       No fractional shares of Common Stock will be issued in conjunction
with any exercise hereunder, but in lieu of such fractional shares the
Company shall make a cash payment therefore on the basis of the Warrant Price
then in effect.

       8.     COMPLIANCE WITH SECURITIES ACT.

       The Holder of this Warrant, by acceptance hereof, agrees that this
Warrant and the shares of Common Stock to be issued on exercise hereof are
being acquired for investment and that it will not offer, sell or otherwise
dispose of this Warrant or any shares of Common Stock to be issued upon
exercise hereof except under circumstances which will not result in a
violation of the Securities Act of 1933, as amended (the "Act"). This Warrant
and all shares of Common Stock issued upon exercise of this Warrant (unless
registered under the Act) shall be stamped and imprinted with a legend
substantially in the following form:

       "THIS SECURITY HAS NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933,
       AS AMENDED (THE ACT"), OR APPLICABLE STATE SECURITIES LAWS AND MAY NOT BE
       TRANSFERRED OR OTHERWISE DISPOSED OF UNLESS IT HAS BEEN REGISTERED UNDER
       THE ACT AND SUCH LAWS OR (1) REGISTRATION UNDER SUCH LAWS IS NOT REQUIRED
       AND (2) AN OPINION OF COUNSEL SATISFACTORY TO THE COMPANY IS FURNISHED TO
       THE COMPANY TO THE EFFECT THAT REGISTRATION UNDER THE ACT AND THE
       APPLICABLE STATE SECURITIES LAWS IS NOT REQUIRED."

       9.     TRANSFER AND EXCHANGE OF WARRANT.

       This Warrant is not transferrable or exchangeable without the consent
of the Company.

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       10.    MISCELLANEOUS.

              (a) NO RIGHTS AS SHAREHOLDER. The Holder of this Warrant shall
not be entitled to vote or receive dividends or be deemed the Holder of
Common Stock or any other securities of the Company that may at any time be
issuable on the exercise hereof for any purpose, nor shall anything contained
herein be construed to confer upon the Holder of this Warrant, as such, any
of the rights of a shareholder of the Company or any right to vote for the
election of directors or upon any matter submitted to shareholders at any
meeting thereof, or to give or withhold consent to any corporate action
(whether upon any recapitalization, issuance of stock, reclassification of
stock, change of par value or change of stock to no par value, consolidation,
merger, conveyance or otherwise) or to receive notice of meetings, or to
receive dividends or subscription rights or otherwise until the Warrant shall
have been exercised and the shares purchasable upon the exercise hereof shall
have become deliverable, as provided herein.

              (b) REPLACEMENT. On receipt of evidence reasonably satisfactory
to the Company of the loss, theft, destruction, or mutilation of this Warrant
and, in the case of mutilation, on surrender and cancellation of this
Warrant, the Company, at its expense, will execute and deliver, in lieu of
this Warrant, a new Warrant of like tenor.

              (c) NOTICE. Any notice given to either party under this Warrant
shall be in writing, and any notice hereunder shall be deemed to have been
given upon the earlier of delivery thereof by hand delivery, by courier, or
by standard form of telecommunication or three (3) business days after the
mailing thereof in the U.S. mail if sent registered mail with postage
prepaid, addressed to the Company at its principal executive offices and to
the Holder at its address set forth in the Company's books and records or at
such other address as the Holder may have provided to the Company in writing.

              (d) GOVERNING LAW. This Warrant shall be governed and construed
under the laws of the State of California.

       This Warrant is executed as of this 10th day of December, 1999.

                                          ACACIA RESEARCH CORPORATION

                                          By:
                                                 -------------------------------

                                          Name:
                                                 -------------------------------

                                          Title:
                                                 -------------------------------

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                                    EXHIBIT 1

                               NOTICE OF EXERCISE

TO:    ACACIA RESEARCH CORPORATION

       1. The undersigned hereby elects to purchase ___________ shares of
Common Stock of Acacia Research Corporation pursuant to the terms of the
attached Warrant, and tenders herewith payment of the purchase price of such
shares in full.

       2. Please issue a certificate or certificates representing said shares
of Common Stock in the name of the Holder at the address specified below:

              (Name)

              (Address)

              (Address)

       3. The undersigned represents that the aforesaid shares of Common
Stock are being acquired for the account of the undersigned for investment
and not with a view to, or for resale in connection with, the distribution
thereof and that the undersigned has no present intention of distributing or
reselling such shares.

                                                   (Name of Holder)

                                                   (Signature of Holder)Exhibit 10.1

                     SECOND AMENDMENT TO LICENSE AGREEMENTS

Effective Date:  December 7, 1999

PARTIES:

Quantech, Ltd.                                       (herein called "Quantech")
a Minnesota corporation
1419 Energy Park Drive
Saint Paul, Minnesota  55108

The Perkin-Elmer Corporation                              (herein called "PE")
a New York Corporation
for its PE Biosystems Division
761 Main Avenue
Norwalk, Connecticut  06589-0001

RECITALS:

A. Quantech and PE are parties to (i) a certain agreement with an effective date
of 16 December, 1997, as amended by the Amendment to License Agreements dated
November 4, 1999 (the "Quantech License Agreement"), pursuant to which, among
other things, Quantech granted to PE a license under the Serono Technology and
Quantech Intellectual Property, and (ii) the Perkin Elmer/Quantech License
Agreement with an effective date of 29 June 1998, as amended by the Amendment to
License Agreements dated November 4, 1999, pursuant to which, among other
things, PE granted a license to certain PE technology described in a patent
application entitled "Surface Plasmon Array System" (the "PE License
Agreement").

B. The parties are shareholders of NEWCO, a Minnesota corporation.

C. The parties desire to amend the Quantech License Agreement and the PE License
Agreement as hereinafter set forth, and, for and in consideration of the mutual
promises set forth herein, and for other good and valuable consideration, the
receipt of which is hereby acknowledged, the parties hereby agree as follows:

1.       DEFINITIONS

1.1      Capitalized terms not defined herein shall have the definitions set
         forth in the Quantech License Agreement, or, in sections of this
         Agreement that amend the PE License Agreement, set forth in the PE
         License Agreement.

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1.2      "Agreements" means the Quantech License Agreement and the PE License
         Agreement.

2.       AGREEMENT TO SUBLICENSE. Quantech agrees that PE may sublicense any and
         all rights under the Quantech License Agreement to NEWCO.

3.       AMENDMENTS TO AGREEMENTS. The Agreements are hereby amended as follows:

         3.1 The parties acknowledge that no PE Intellectual Property arose from
         a joint development effort with Quantech pursuant to Section 3.1 of the
         Quantech License Agreement, and that Sections 3.1, 3.2 and 4.2 of the
         Quantech License Agreement will only be applicable in the event PE
         receives back from Newco any of the rights sublicensed by PE to Newco
         pursuant to the Perkin Elmer/Newco License and Sublicense Agreement.

         3.2 Sections 5.1 and 5.3 of the Quantech License Agreement are deleted
         in their entirety, so that, among other things, no minimum royalties
         will be required from PE.

         3.3 Section 5.4 of the Quantech License Agreement will be replaced in
         its entirety by the following:

                  "Status Reports. If PE or Newco as its Sublicensee shall not
                  have begun selling Licensed Products by March 31, 2001, on or
                  before the forty fifth (45th) day after the end of each
                  Calendar Quarter beginning with the calendar quarter ending
                  June 30, 2001, PE or the Sublicensee shall deliver to Quantech
                  a Statement of Intent signed by a duly authorized employee of
                  PE or the Sublicensee stating that PE or the Sublicensee is
                  continuing to pursue research and development efforts with an
                  intent to commercialize, or is continuing commercialization
                  of, Licensed Products. The obligation to provide such
                  quarterly Statements of Intent shall terminate upon the
                  earlier of the sale of the first Licensed Product or payment
                  of first royalty payment under Section 5.2. If PE or the
                  Sublicensee shall fail to timely deliver a Statement of
                  Intent, Quantech may notify PE and the Sublicensee of this
                  failure. If PE or the Sublicensee fails to deliver the
                  Statement of Intent within two months of Quantech's notice,
                  PE's license and the Sublicensee's sublicense rights granted
                  in Section 2 shall immediately terminate".

         3.4 Section 5.2(a) of the Quantech License Agreement is amended by
         inserting the following words at the beginning of the first sentence of
         Section 5.2(a), "In the event that the sublicense agreement of even
         date herewith between PE and Newco is terminated,".

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         3.5 Section 5.2(b) of the Quantech License Agreement is amended by
         inserting the following words at the beginning of the first sentence of
         Section 5.2(b), "In the event that the sublicense agreement of even
         date herewith between PE and Newco is terminated".

         3.6 Section 3.1 of the PE License Agreement is deleted in its entirety.

         3.7 Section 4.2 of the PE License is deleted in its entirety so that no
         minimum royalties will be required from Quantech, effective the date of
         this Second Amendment to License Agreement.

4.       AGREEMENTS OTHERWISE IN FULL FORCE AND EFFECT.

Except as expressly set forth in this Amendment, the Agreements shall remain in
full force and effect in accordance with their terms.

IN WITNESS WHEREOF, each of the parties has caused this agreement to be executed
in the manner appropriate to each, effective as of the date first above written

Quantech, Ltd.                                 The Perkin-Elmer Corporation

By:____________________________                By:_____________________________
     Robert Case, CEO
                                               Name:___________________________

                                               Title:__________________________

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