Document:

<PAGE>

                                                                     Exhibit 4.1

                               RIGHTS AGREEMENT

                        RIBOZYME PHARMACEUTICALS, INC.

                                      and

                   AMERICAN STOCK TRANSFER & TRUST COMPANY,
                                as Rights Agent

                         Dated as of November 22, 2000
<PAGE>

                               TABLE OF CONTENTS

<TABLE>
<CAPTION>
                                                                                      Page
                                                                                      ----
<S>  <C>                                                                              <C>
 1.  Certain Definitions..............................................................   1
 2.  Appointment of Rights Agent......................................................   4
 3.  Issue of Right Certificates......................................................   5
 4.  Form of Right Certificates.......................................................   6
 5.  Countersignature and Registration................................................   7
 6.  Transfer, Split Up, Combination and Exchange of Right Certificates;
          Mutilated, Destroyed, Lost or Stolen Right Certificates.....................   8
 7.  Exercise of Rights; Purchase Price; Expiration Date of Rights....................   9
 8.  Cancellation and Destruction of Right Certificates...............................  11
 9.  Reservation and Availability of Shares of Series AA Preferred Stock..............  11
10.  Series AA Preferred Stock Record Date............................................  12
11.  Adjustment of Purchase Price, Number of Shares or Number of Rights...............  12
12.  Certificate of Adjusted Purchase Price or Number of Shares.......................  19
13.  Consolidation, Merger or Sale or Transfer of Assets or Earning Power.............  20
14.  Fractional Rights and Fractional Shares..........................................  22
15.  Rights of Action.................................................................  24
16.  Agreement of Right Holders.......................................................  24
17.  Right Certificate Holder Not Deemed a Stockholder................................  24
18.  Concerning the Rights Agent......................................................  25
19.  Merger or Consolidation or Change of Name of Rights Agent........................  25
20.  Duties of Rights Agent...........................................................  26
21.  Change of Rights Agent...........................................................  28
22.  Issuance of New Right Certificates...............................................  29
23.  Redemption and Termination.......................................................  29
24.  Exchange.........................................................................  30
25.  Notice of Proposed Actions.......................................................  31
26.  Notices..........................................................................  32
27.  Supplements and Amendments.......................................................  33
28.  Successors.......................................................................  33
29.  Benefits of This Rights Agreement................................................  33
30.  Severability.....................................................................  34
31.  Governing Law....................................................................  34
32.  Counterparts.....................................................................  34
33.  Descriptive Headings.............................................................  34
</TABLE>
<PAGE>

                               RIGHTS AGREEMENT

          This Rights Agreement, dated as of November 22, 2000 (the "Rights
Agreement"), is entered into between Ribozyme Pharmaceuticals, Inc., a Delaware
corporation (the "Company"), and American Stock Transfer & Trust Company (the
"Rights Agent").

                              W I T N E S S E T H

     WHEREAS, on November 21, 2000, the Board of Directors (as hereinafter
defined) authorized and declared a dividend distribution of one right (each a
"Right" and collectively the "Rights") for each share of Common Stock (as
hereinafter defined) of the Company outstanding at the close of business on
December 8, 2000 (the "Record Date"), and has authorized the issuance of one
Right in respect of each share of common stock of the Company issued between the
Record Date and the Distribution Date (as such term is defined in Section 3
hereof), each Right representing the right to purchase one one-hundredths of a
share of Series AA Preferred Stock of the Company having the rights, powers and
preferences set forth in the form of Certificate of Designation attached hereto
as Exhibit A, upon the terms and subject to the conditions hereinafter set
forth; and

          WHEREAS, the Company desires to appoint the Rights Agent to act as
provided herein, and the Rights Agent is willing to so act.

          NOW, THEREFORE, in consideration of the premises and the mutual
agreements herein set forth, the parties hereby agree as follows:

      1.     Certain Definitions.  For purposes of this Rights Agreement, the
             -------------------
following terms have the meanings indicated:

             (a) "Acquiring Person" shall mean any Person (as hereinafter
defined) who or which, together with all Affiliates (as hereinafter defined) and
Associates (as hereinafter defined) of such Person, without the Prior Written
Approval of the Company (as hereinafter defined), shall be the Beneficial Owner
(as hereinafter defined) of securities of the Company constituting 15% or more
of the Voting Power (as hereinafter defined) of the Company or was such a
Beneficial Owner at any time after the date hereof, whether or not such Person
continues to be the Beneficial Owner of securities representing 15% or more of
the Voting Power of the Company, but shall not include (i) the Company, any
Subsidiary (as hereinafter defined) of the Company, any employee benefit plan or
compensation arrangement of the Company or any Subsidiary of the Company, or any
entity holding securities of the Company to the extent organized, appointed or
established by the Company or any Subsidiary of the Company for or pursuant to
the terms of any such employee benefit plan or compensation arrangement, or (ii)
any Person who or which, together with all Affiliates and Associates of such
Person, inadvertently may become the Beneficial Owner of securities of the
Company representing 15% or more of the Voting Power of the Company, so long as
such Person, individually or together with the Affiliates and Associates of such
Person, (y) within 8 Business Days (as hereinafter defined) after such Person
would have become an Acquiring Person (but for the operation of this
<PAGE>

clause) delivers written notice to the Board of Directors that such Person did
so inadvertently and (z) within 5 Business Days after such notice divests
(without exercising or retaining any power, including voting, with respect to
such securities), sufficient securities of the Company so that such Person,
together with all Affiliates and Associates of such Person, ceases to be the
Beneficial Owner of 15% or more of the Voting Power of the Company.
Notwithstanding the foregoing, no Person shall become an "Acquiring Person" as
the result of an acquisition of voting securities of the Company by the Company
which, by reducing the amount of such securities outstanding, increases the
proportionate voting power of such securities beneficially owned by such Person
to 15% or more of the Voting Power; provided, however, that if a Person becomes
the Beneficial Owner of securities constituting 15% or more of the Voting Power
of the Company by reason of purchases by the Company and shall, after such
purchases by the Company, become the Beneficial Owner of additional securities
constituting 1% or more of the Voting Power of the Company without the Prior
Written Approval of the Company, then such Person shall be deemed to be an
Acquiring Person.

          (b)  "Affiliate" and "Associate" shall have the respective meanings
ascribed to such terms in Rule 12b-2 of the rules and regulations promulgated
under the Securities Exchange Act of 1934, as amended (the "Exchange Act"), as
in effect on the date hereof.

          (c)  A Person shall be deemed the "Beneficial Owner" of, and shall be
deemed to "beneficially own," any securities:

               (i)  which such Person or any of such Person's Affiliates or
Associates beneficially owns, directly or indirectly as determined pursuant to
Rule 13d-3 of the rules and regulations under the Exchange Act, as in effect on
the date hereof;

               (ii) which such Person or any of such Person's Affiliates or
Associates has (A) the right to acquire (whether such right is exercisable
immediately or only after the passage of time) pursuant to any agreement,
arrangement or understanding (other than customary agreements with and between
underwriters and selling group members with respect to a bona fide public
offering of securities), or upon the exercise of conversion rights, exchange
rights, rights (other than these Rights), warrants or options, or otherwise;
provided, however, that a Person shall not be deemed the "Beneficial Owner" of
securities tendered pursuant to a tender or exchange offer made by or on behalf
of such Person or any of such Person's Affiliates or Associates until such
tendered securities are accepted for payment or exchange; or (B) the right to
vote pursuant to any agreement, arrangement or understanding; provided, however,
that a Person shall not be deemed the "Beneficial Owner" of any security under
this clause (B) if the agreement, arrangement or understanding to vote such
security (1) arises solely from a revocable proxy or consent given in response
to a public proxy or consent solicitation made pursuant to, and in accordance
with, the applicable rules and regulations under the Exchange Act and (2) is not
also then reportable by such person on Schedule 13D under the Exchange Act (or
any comparable or successor report); or

                                      -2-
<PAGE>

               (iii) which are beneficially owned, directly or indirectly, by
any other Person with which such Person or any of such Person's Affiliates or
Associates has any agreement, arrangement or understanding (other than customary
agreements with and between underwriters and selling group members with respect
to a bona fide public offering of securities) for the purpose of acquiring,
holding, voting (except pursuant to a revocable proxy or consent as described in
clause (B) of subparagraph (ii) of this paragraph (c)) or disposing of any
securities of the Company.

          Notwithstanding anything in this definition of Beneficial Ownership to
the contrary, the phrase "then outstanding," when used with reference to a
Person's Beneficial Ownership of securities of the Company, shall mean the
number of such securities then issued and outstanding together with the number
of such securities not then actually issued and outstanding which such Person
would be deemed to own beneficially hereunder.

          (d)  "Board of Directors" shall mean the Board of Directors of the
Company as constituted from time to time.

          (e)  "Business Day" shall mean any day other than a Saturday, Sunday,
or a day on which banking institutions in the State of Colorado are authorized
or obligated by law or executive order to close.

          (f)  "Close of Business" on any given date shall mean 5:00 p.m.,
Boulder, Colorado, time, on such date; provided, however, that if such date is
not a Business Day it shall mean 5:00 p.m., Boulder, Colorado, time, on the next
succeeding Business Day.

          (g)  "Common Stock" shall mean the common stock, par value $0.01 per
share, of the Company, except that "Common Stock" when used with reference to
any Person other than the Company shall mean the capital stock with the greatest
Voting Power of such Person or the equity securities or other equity interest
having power to control or direct the management of such Person or, if such
Person is a Subsidiary of another Person, of the Person which ultimately
controls such first-mentioned Person and which has issued and outstanding such
capital stock, equity securities or equity interests.

          (h)  "Distribution Date" shall have the meaning set forth in Section 3
hereof.

          (i)  "Expiration Date" shall have the meaning set forth in Section
7(a) hereof.

          (j)  "Final Expiration Date" shall have the meaning set forth in
Section 7(a) hereof.

          (k)  "Person" shall mean any individual, firm, corporation,
partnership or other entity, and shall include any successor (by merger or
otherwise) of any such entity.

                                      -3-
<PAGE>

          (l)  "Series AA Preferred Stock" shall mean the Series AA Junior
Participating Preferred Stock, par value $0.01 per share, of the Company having
the rights and preferences set forth in the Form of Certificate of Designation
attached to this Agreement as Exhibit A.

          (m)  "Prior Written Approval of the Company" shall mean prior express
written consent of the Company to the actions in question, executed on behalf of
the Company by a duly authorized officer of the Company following express
approval by action of a majority of the members of the Board of Directors then
in office.

          (n)  "Purchase Price" shall have the meaning set forth in Section 7(b)
hereof.

          (o)  "Redemption Price" shall have the meaning set forth in Section
23(a) hereof.

          (p)  "Flip-in Event" shall have the meaning set forth in Section
11(b)(i) hereof.

          (q)  "Flip-over Event" shall mean an event described in clauses (x),
(y) or (z) of Section 13(a) hereof.

          (r)  "Stock Acquisition Date" shall mean the earlier of (i) the first
date of public announcement by a Person that an Acquiring Person has become an
Acquiring Person, or (ii) the date on which the Company first has notice, direct
or indirect, or otherwise determines that a Person has become an Acquiring
Person.

          (s)  "Subsidiary" shall mean, with respect to any Person, any other
Person of which securities or other ownership interests having ordinary Voting
Power, in the absence of contingencies, to elect a majority of the board of
directors (or other persons performing similar functions) of such other Person
are at the time directly or indirectly owned by such Person or one or more of
such Person's Subsidiaries, except that "Subsidiary" when used with reference to
the Company shall mean any Person of which either a majority of the Voting Power
of the voting equity securities or a majority of the equity interests is owned,
directly or indirectly, by the Company.

          (t)  "Voting Power" shall mean the voting power of all securities of a
Person then outstanding generally entitled to vote for the election of directors
of the Person (or, where appropriate, for the election of persons performing
similar functions).

      2.  Appointment of Rights Agent.  The Company hereby appoints the Rights
          ---------------------------
Agent to act as agent for the Company in accordance with the terms and
conditions hereof, and the Rights Agent hereby accepts such appointment. The
Company may from time to time appoint such co-Rights Agents as it may deem
necessary or desirable. In the event the Company appoints one or more co-Rights
Agents, the respective duties of the Rights Agent and any co-Rights Agents shall
be as the Company shall determine.

                                      -4-
<PAGE>

      3.  Issue of Right Certificates.
          ---------------------------

          (a)  Until the earlier of (i) the Close of Business on the tenth
Business Day after the Stock Acquisition Date or (ii) the Close of Business on
the tenth Business Day (or such later date as may be determined by action of the
Board of Directors but in no event later than the tenth Business Day after such
time as any Person becomes an Acquiring Person) after the date that a tender or
exchange offer by any Person (other than the Company, any Subsidiary of the
Company, any employee benefit plan or compensation arrangement of the Company or
of any Subsidiary of the Company, or any entity holding securities of the
Company to the extent organized, appointed or established by the Company or any
Subsidiary of the Company for or pursuant to the terms of any such employee
benefit plan or compensation arrangement) is commenced within the meaning of
Rule 14d-2(a) of the rules and regulations under the Exchange Act, without the
Prior Written Approval of the Company, which tender or exchange offer would
result in any Person becoming the Beneficial Owner of Voting Power of the
Company aggregating 15% or more of the outstanding Voting Power of the Company
(including any such date which is after the date of this Rights Agreement and
prior to the issuance of the Rights; the earlier of such dates being herein
referred to as the "Distribution Date"), (x) the Rights will be evidenced
(subject to the provisions of paragraph (b) of this Section 3) by the
certificates for the Common Stock registered in the names of the holders of the
Common Stock (which certificates for Common Stock shall be deemed also to be
Right Certificates) and not by separate Right Certificates, as more fully set
forth below, and (y) the Rights (and the right to receive certificates therefor)
will be transferable only in connection with the transfer of the underlying
shares of Common Stock, as more fully set forth below.  As soon as practicable
after the Company has notified the Rights Agent of the occurrence of the
Distribution Date and provided the Rights Agent with all necessary information,
the Company shall prepare and execute, and the Rights Agent shall countersign
and send, by first-class, insured, postage prepaid mail, to each record holder
of the Common Stock as of the Close of Business on the Distribution Date, at the
address of such holder shown on the records of the Company, a right certificate,
in substantially the form of Exhibit B hereto (the "Right Certificate"),
evidencing one Right for each share of Common Stock so held, subject to
adjustment as provided herein.  As of and after the Distribution Date, the
Rights will be evidenced solely by such Right Certificates.

          (b)  On the Record Date or as soon as practicable thereafter, the
Company will send a copy of a Summary of Rights to Purchase Series AA Preferred
Stock, in substantially the form of Exhibit C hereto (the "Summary of Rights"),
by first-class, postage prepaid mail, to each record holder of the Common Stock
as of the Close of Business on the Record Date, at the address of such holder
shown on the records of the Company.  With respect to certificates for the
Common Stock outstanding as of the Record Date, until the Distribution Date (or
the earlier redemption, expiration or termination of the Rights), the Rights
will be evidenced by such certificates for the Common Stock registered in the
names of the holders of the Common Stock and the registered holders of the
Common Stock shall also be registered holders of the associated Rights. Until
the Distribution Date (or the earlier redemption, expiration or termination of
the Rights), the surrender for transfer of any of the certificates for the
Common Stock outstanding in

                                      -5-
<PAGE>

respect of which Rights have been issued shall also constitute the transfer of
the Rights associated with the Common Stock represented by such certificate.

          (c)  Certificates for the Common Stock issued after the Record Date
but prior to the earlier of the Distribution Date or the redemption, expiration
or termination of the Rights shall be deemed also to be certificates for Rights
and shall have impressed, printed or written on, or otherwise affixed to them a
legend substantially to the following effect:

          This certificate also evidences and entitles the holder hereof to
          certain Rights as set forth in a Rights Agreement dated as of November
          22, 2000, between Ribozyme Pharmaceuticals, Inc. (the "Company") and
          American Stock Transfer & Trust Company (the "Rights Agreement"), as
          it may from time to time be supplemented or amended, the terms of
          which are incorporated herein by reference and a copy of which is on
          file at the principal executive offices of the Company.  Under certain
          circumstances, as set forth in the Rights Agreement, such Rights may
          expire or may be redeemed, exchanged or be evidenced by separate
          certificates and no longer be evidenced by this certificate.  The
          Company will mail to the holder of this certificate a copy of the
          Rights Agreement without charge promptly after receipt of a written
          request therefor. Under certain circumstances, Rights issued to or
          held by Acquiring Persons or their Affiliates or Associates (as
          defined in the Rights Agreement) and any subsequent holder of such
          Rights may become null and void.

With respect to such certificates containing the foregoing legend, until the
Distribution Date (or the earlier redemption, expiration or termination of the
Rights), the Rights associated with the Common Stock represented by such
certificates shall be evidenced by such certificates alone, and the surrender
for transfer of any of such certificates shall also constitute the transfer of
the Rights associated with the Common Stock represented by such certificates.

     In the event that the Company purchases or acquires any Common Stock after
the Record Date but prior to the Distribution Date, any Rights associated with
such Common Stock shall be deemed canceled and retired so that the Company shall
not be entitled to exercise any Rights associated with shares of Common Stock
which are no longer outstanding.

     4.   Form of Right Certificates.
          --------------------------

          (a)  The Right Certificates (and the forms of election to purchase
Series AA Preferred Stock and of assignment to be printed on the reverse
thereof) shall be in substantially the same form as Exhibit B hereto and may
have such marks of identification or designation and such legends, summaries or
endorsements printed thereon as the Company may deem appropriate (but which do
not affect the duties or responsibilities of the Rights Agent) and as are

                                      -6-
<PAGE>

not inconsistent with the provisions of this Rights Agreement, or as may be
required to comply with any applicable law, rule or regulation or with any rule
or regulation of any stock exchange on which the Rights may from time to time be
listed, or to conform to customary usage. Subject to the provisions of Section
11 and Section 22 hereof, the Right Certificates, whenever issued, shall be
dated as of the Record Date, and on their face shall entitle the holders thereof
to purchase such number of one one-hundredths of a share of Series AA Preferred
Stock as shall be set forth therein at the Purchase Price, but the number and
identity of such shares and the Purchase Price shall be and remain subject to
adjustment as provided herein.

          (b)  Any Right Certificate issued pursuant hereto that represents
Rights beneficially owned by (i) an Acquiring Person or any Associate or
Affiliate of an Acquiring Person, (ii) a transferee of an Acquiring Person (or
of any such Associate or Affiliate) which becomes a transferee after the
Acquiring Person becomes such, or (iii) a transferee of an Acquiring Person (or
of any such Associate or Affiliate) which becomes a transferee prior to or
concurrently with the Acquiring Person becoming such and which receives such
Rights pursuant to either (A) a transfer (whether or not for consideration) from
the Acquiring Person (or any such Associate or Affiliate) to holders of equity
interests in such Acquiring Person (or such Associate or Affiliate) or to any
Person with whom such Acquiring Person (or such Associate or Affiliate) has any
continuing agreement, arrangement or understanding regarding either the
transferred Rights, shares of Company Common Stock or the Company or (B) a
transfer which a majority of the Board of Directors has determined to be part of
an agreement, arrangement or understanding which has as a primary purpose or
effect the avoidance of Section 7(e) hereof, and any Right Certificate issued
pursuant to Section 6 hereof, Section 11 hereof or Section 22 hereof upon
transfer, exchange, replacement or adjustment of any other Right Certificate
referred to in this sentence, shall contain (to the extent the Rights Agent has
notice and to the extent feasible) the following legend:

          The Rights represented by this Right Certificate are or were
          beneficially owned by a Person who was or became an Acquiring Person
          or an Affiliate or an Associate of an Acquiring Person. Accordingly,
          this Right Certificate and the Rights represented hereby are void in
          the circumstances specified in Section 7(e) of the Rights Agreement.

The failure to print the foregoing legend on any such Right Certificate or any
defect therein shall not affect in any manner whatsoever the application or
interpretation of the provisions of Section 7(e) hereof.

      5.  Countersignature and Registration.
          ---------------------------------

          (a)  The Right Certificates shall be executed on behalf of the Company
by its Chairman of the Board, Chief Executive Officer, President, Chief
Financial Officer or any Vice President, either manually or by facsimile
signature, and shall have affixed thereto the Company's seal or a facsimile
thereof which shall be attested by the Secretary or an Assistant

                                      -7-
<PAGE>

Secretary of the Company, either manually or by facsimile signature. The Right
Certificates shall be countersigned manually or by facsimile signature by the
Rights Agent and shall not be valid for any purpose unless so countersigned. In
case any officer of the Company whose manual or facsimile signature is affixed
to the Right Certificates shall cease to be such officer of the Company before
countersignature by the Rights Agent and issuance and delivery by the Company,
such Right Certificates, nevertheless, may be countersigned by the Rights Agent,
issued and delivered with the same force and effect as though the person who
signed such Right Certificates had not ceased to be such officer of the Company.
Any Right Certificate may be signed on behalf of the Company by any person who,
at the actual date of the execution of such Right Certificate, shall be a proper
officer of the Company to sign such Right Certificate, although at the date of
the execution of this Rights Agreement any such person was not such an officer.

          (b)  Following the Distribution Date and receipt by the Rights Agent
of any relevant information, the Rights Agent will keep or cause to be kept, at
its stockholder services office or such other office designated for such
purpose, books for registration and transfer of the Right Certificates issued
hereunder. Such books shall show the names and addresses of the respective
holders of the Right Certificates, the number of Rights evidenced on its face by
each of the Right Certificates, the certificate number of each of the Right
Certificates and the date of each of the Right Certificates.

      6.  Transfer, Split Up, Combination and Exchange of Right Certificates;
          -------------------------------------------------------------------
Mutilated, Destroyed, Lost or Stolen Right Certificates.
-------------------------------------------------------

          (a)  Subject to the provisions of Sections 4(b), 7(e) and 14 hereof,
at any time after the Close of Business on the Distribution Date, and at or
prior to the Close of Business on the Expiration Date, any Right Certificate or
Right Certificates may be transferred, split up, combined or exchanged for
another Right Certificate or Right Certificates, entitling the registered holder
to purchase a like number of one one-hundredths shares of Series AA Preferred
Stock as the Right Certificate or Right Certificates surrendered then entitled
such holder to purchase. Any registered holder desiring to transfer, split up,
combine or exchange any Right Certificate shall make such request in writing
delivered to the Rights Agent, and shall surrender the Right Certificate or
Right Certificates to be transferred, split up, combined or exchanged at the
stockholder services office of the Rights Agent or such office designated for
such purpose. Thereupon, the Rights Agent shall countersign and deliver to the
person entitled thereto a Right Certificate or Right Certificates, as the case
may be, as so requested. The Company may require payment of a sum sufficient to
cover any tax or governmental charge that may be imposed in connection with any
transfer, split up, combination or exchange of Right Certificates.

          (b)  Upon receipt by the Company and the Rights Agent of evidence
reasonably satisfactory to them of the loss, theft, destruction or mutilation of
a Right Certificate, and, in case of loss, theft or destruction, of indemnity or
security satisfactory to them, and reimbursement to the Company and the Rights
Agent of all reasonable expenses incidental thereto, and upon surrender to the
Rights Agent and cancellation of the Right Certificate if

                                      -8-
<PAGE>

mutilated, the Company will make and deliver a new Right Certificate of like
tenor to the Rights Agent for countersignature and delivery to the registered
owner in lieu of the Right Certificate so lost, stolen, destroyed or mutilated.

      7.  Exercise of Rights; Purchase Price; Expiration Date of Rights.
          -------------------------------------------------------------

          (a)  The registered holder of any Right Certificate may exercise the
Rights evidenced thereby (except as otherwise provided herein) in whole or in
part at any time after the Distribution Date upon surrender of the Right
Certificate, with the form of election to purchase on the reverse side thereof
duly and properly executed, to the Rights Agent at the stockholder services
office of the Rights Agent or such office designated for such purpose, together
with payment of the Purchase Price for each one one-hundredths of a share of
Series AA Preferred Stock as to which the Rights are exercised, at or prior to
the Close of Business on the Expiration Date. The "Expiration Date," as used in
this Rights Agreement, shall be the earliest of (i) the Final Expiration Date
(as defined below), (ii) the time at which the Rights are redeemed as provided
in Section 23 hereof, or (iii) the time at which the Rights are exchanged as
provided in Section 24 hereof. The "Final Expiration Date," as used in this
Rights Agreement, shall be December 8, 2010.

          (b)  The "Purchase Price" for each one one-hundredths of a share of
Series AA Preferred Stock pursuant to the exercise of a Right shall be as set
forth on the face of the Right Certificates, shall initially be $300.00, shall
be subject to adjustment from time to time as provided in Sections 11 and 13
hereof and shall be payable in lawful money of the United States of America in
accordance with paragraph (c) below.

          (c)  Upon receipt of a Right Certificate, with the form of election to
purchase duly and properly executed, accompanied by payment of the Purchase
Price for each one one-hundredth of a share of Series AA Preferred Stock to be
purchased and an amount equal to any applicable tax or charge required to be
paid by the holder of the Rights pursuant hereto in accordance with Section 9
hereof by certified check, bank draft or money order payable to the order of the
Company or the Rights Agent, the Rights Agent shall, subject to Section 20(k)
hereof, thereupon promptly (i) either (A) requisition from any transfer agent of
the one one-hundredths of a share of Series AA Preferred Stock (or make
available, if the Rights Agent is the transfer agent) certificates for the
number of one one-hundredths of a share of Series AA Preferred Stock to be
purchased and the Company hereby irrevocably authorizes any such transfer agent
to comply with all such requests, or (B) if the Company, in its sole discretion,
shall have elected to deposit the shares of Series AA Preferred Stock issuable
upon exercise of the Rights hereunder into a depositary, requisition from the
depositary agent depositary receipts representing such number of one one-
hundredths of a share of Series AA Preferred Stock as are to be purchased (in
which case certificates for the shares of Series AA Preferred Stock represented
by such receipts shall be deposited by the transfer agent with the depositary
agent) and the Company hereby directs such depositary agent to comply with all
such requests, (ii) promptly after receipt of such certificates or depositary
receipts cause the same to be delivered to or upon the order of the registered
holder of such Right Certificate, registered in such name or

                                      -9-
<PAGE>

names as may be designated by such holder, (iii) when appropriate, requisition
from the Company the amount of cash to be paid in lieu of issuance of fractional
shares in accordance with Section 14 hereof, (iv) after receipt of any such
cash, promptly deliver such cash to or upon the order of the registered holder
of such Right Certificate, (v) when appropriate, requisition from the Company
the amount of cash, property or securities issuable upon exercise of a Right
pursuant to the adjustment provisions of Section 11 or the exchange provisions
of Section 24, and (vi) after receipt of any such cash, property or securities,
promptly deliver such cash, property or securities to or upon the order of the
registered holder of such Right Certificate, of any such cash or securities.

          (d)  In case the registered holder of any Right Certificate shall
exercise less than all the Rights evidenced thereby, a new Right Certificate
evidencing Rights equivalent to the Rights remaining unexercised shall be issued
by the Rights Agent to the registered holder of such Right Certificate or to
such holder's duly authorized assigns, subject to the provisions of Section 14
hereof.

          (e)  Notwithstanding anything in this Rights Agreement to the
contrary, upon the first occurrence of a Flip-in Event or a Flip-over Event, any
Rights which are then or become beneficially owned by (i) an Acquiring Person or
an Associate or Affiliate of an Acquiring Person, (ii) a transferee of an
Acquiring Person (or of any such Associate or Affiliate) which becomes a
transferee after the Acquiring Person becomes such, or (iii) a transferee of an
Acquiring Person (or of any such Associate or Affiliate) which becomes a
transferee prior to or concurrently with the Acquiring Person becoming such and
which receives such Rights pursuant to either (A) a transfer (whether or not for
consideration) from the Acquiring Person (or any such Associate or Affiliate) to
holders of equity interests in such Acquiring Person (or any such Associate or
Affiliate) or to any Person with whom such Acquiring Person (or such Associate
or Affiliate) has any continuing agreement, arrangement or understanding
regarding the transferred Rights, shares of Company Common Stock or the Company
or (B) a transfer which a majority of the Board of Directors has determined to
be part of an agreement, arrangement or understanding which has as a primary
purpose or effect the avoidance of this Section 7(e), shall be null and void
without any further action, and no holder of such Rights shall have any rights
whatsoever with respect to such Rights, whether under any provision of this
Agreement or otherwise. The Company shall use all reasonable efforts to ensure
that the provisions of this Section 7(e) and Section 4(b) are complied with
(including notifying the Rights Agent thereof), but neither the Company nor the
Rights Agent shall have any liability to any holder of Rights or any other
Person as a result of the Company' s failure to make any determination under
this Section 7(e) or Section 4(b) with respect to an Acquiring Person or its
Affiliates, Associates or transferees hereunder.

          (f)  Notwithstanding anything in this Rights Agreement to the
contrary, neither the Rights Agent nor the Company shall be obligated to
undertake any action with respect to a registered holder upon the occurrence of
any purported exercise as set forth in this Section 7 unless the certificate
contained in the appropriate form of election to purchase set forth on the
reverse side of the Right Certificate surrendered for such exercise shall have
been

                                      -10-
<PAGE>

properly completed and duly executed by the registered holder thereof and the
Company or the Rights Agent shall have been provided with such additional
evidence of the identity of the Beneficial Owner (or former Beneficial Owner) or
Affiliates or Associates thereof as the Company or the Rights Agent shall
reasonably request.

      8.  Cancellation and Destruction of Right Certificates.  All Right
          --------------------------------------------------
Certificates surrendered for the purpose of exercise, transfer, split up,
combination or exchange shall, if surrendered to the Company or to any of its
agents, be delivered to the Rights Agent for cancellation or in canceled form,
or, if surrendered to the Rights Agent, shall be canceled by it, and no Right
Certificates shall be issued in lieu thereof except as expressly permitted by
any of the provisions of this Rights Agreement. The Company shall deliver to the
Rights Agent for cancellation and retirement, and the Rights Agent shall so
cancel and retire, any other Right Certificate purchased or acquired by the
Company otherwise than upon the exercise thereof. The Rights Agent shall deliver
all canceled Right Certificates to the Company, or shall, at the written request
of the Company, destroy such canceled Right Certificates, and in such case shall
deliver a certificate of destruction thereof to the Company.

      9.  Reservation and Availability of Shares of Series AA Preferred Stock.
          -------------------------------------------------------------------

          (a) The Company covenants and agrees that it will cause to be reserved
and kept available out of its authorized and unissued shares of Series AA
Preferred Stock the number of shares of Series AA Preferred Stock that will be
sufficient to permit the exercise in full of all outstanding Rights and, after
the occurrence of a Flip-in Event or a Flip-over Event, shall so reserve and
keep available a sufficient number of shares of Series AA Preferred Stock,
Common Stock and/or other securities which may be required to permit the
exercise in full of the Rights pursuant to this Rights Agreement.

          (b) The Company covenants and agrees that it will take all such action
as may be necessary to ensure that all shares of Series AA Preferred Stock
and/or other securities delivered upon exercise of Rights shall, at the time of
delivery of the certificates for such shares or other securities (subject to
payment of the Purchase Price), be duly and validly authorized and issued and
fully paid and nonassessable shares or other securities.

          (c) The Company shall use its best efforts to (i) file, as soon as
practicable following the first occurrence of an event which would establish the
Distribution Date, a registration statement under the Securities Act of 1933, as
amended (the "Securities Act"), with respect to the securities purchasable upon
exercise of the Rights on an appropriate form, (ii) cause such registration
statement to become effective as soon as practicable after such filing, and
(iii) cause such registration statement to remain effective (with a prospectus
at all times meeting the requirements of the Securities Act) until the
Expiration Date. The Company will also take such action as may be appropriate
under the "blue sky" laws of the various states. The Company may temporarily
suspend, for a period of time not to exceed ninety (90) days after the date set
forth in clause (i) of the first sentence of this Section 9(c), the
exercisability of the Rights in order to prepare and file such registration
statement and permit it to become effective. Upon any

                                      -11-
<PAGE>

such suspension, the Company shall issue a public announcement stating that the
exercisability of the Rights has been temporarily suspended, as well as a public
announcement at such time as the suspension is no longer in effect.
Notwithstanding any provision of this Agreement to the contrary, the Rights
shall not be exercisable in any jurisdiction, unless the requisite qualification
in such jurisdiction shall have been obtained and until a registration statement
has been declared effective.

          (d) The Company further covenants and agrees that it will pay when due
and payable any and all federal and state taxes and charges which may be payable
in respect of the issuance or delivery of the Right Certificates or of any
shares of Series AA Preferred Stock and/or other securities upon the exercise of
Rights. The Company shall not, however, be required to pay any tax or charge
which may be payable in respect of any transfer involved in the transfer or
delivery of Right Certificates or the issuance or delivery of certificates or
depositary receipts for Series AA Preferred Stock and/or other securities in a
name other than that of the registered holder of the Right Certificate
evidencing Rights surrendered for exercise, nor shall the Company be required to
issue or deliver any certificates or depositary receipts for shares of Series AA
Preferred Stock and/or other securities upon the exercise of any Rights until
any such tax or charge shall have been paid (any such tax being payable by the
holder of such Right Certificate at the time of surrender) or until it has been
established to the Company's satisfaction that no such tax or charge is due.

      10. Series AA Preferred Stock Record Date.  Each Person (other than the
          -------------------------------------
Company) in whose name any certificate for shares of Series AA Preferred Stock
(or other securities) is issued upon the exercise of Rights shall for all
purposes be deemed to have become the holder of record of the Series AA
Preferred Stock (or other securities) represented thereby on, and such
certificate shall be dated, the date upon which the Right Certificate evidencing
such Rights was duly surrendered and payment of the Purchase Price (and any
applicable taxes or charges) was made; provided, however, that if the date of
such surrender and payment is a date upon which the Series AA Preferred Stock
(or other securities) transfer books of the Company are closed, such person
shall be deemed to have become the record holder of such shares on, and such
certificate shall be dated, the next succeeding Business Day on which the Series
AA Preferred Stock (or other securities) transfer books of the Company are open.
Prior to the exercise of the Rights evidenced thereby, the holder of a Right
Certificate shall not be entitled to any rights of a stockholder of the Company
with respect to shares for which the Rights shall be exercisable, including,
without limitation, the right to vote, to receive dividends or other
distributions or to exercise any preemptive rights, and shall not be entitled to
receive any notice of any proceedings of the Company, except as provided herein.

      11. Adjustment of Purchase Price, Number of Shares or Number of Rights.
          ------------------------------------------------------------------
The Purchase Price, the number and identity of shares covered by each Right and
the number of Rights outstanding are subject to adjustment from time to time as
provided in this Section 11.

          (a) In the event the Company shall at any time after the date of this
Rights Agreement (i) declare a dividend on the Series AA Preferred Stock payable
in shares of Series

                                      -12-
<PAGE>

AA Preferred Stock, (ii) subdivide the outstanding Series AA Preferred Stock,
(iii) combine the outstanding Series AA Preferred Stock into a smaller number of
shares or (iv) issue any shares of its capital stock in a reclassification of
the Series AA Preferred Stock (including any such reclassification in connection
with a consolidation or merger in which the Company is the continuing or
surviving corporation), except as otherwise provided in this Section 11, the
Purchase Price in effect at the time of the record date for such dividend or the
time of the effective date of such subdivision, combination or reclassification,
and the number and kind of shares of capital stock, including Series AA
Preferred Stock, issuable upon exercise of a Right, shall be proportionately
adjusted so that the holder of any Right exercised after such time, upon payment
of the aggregate consideration such holder would have had to pay to exercise
such Right prior to such time, shall be entitled to receive the aggregate number
and kind of shares of capital stock, including Series AA Preferred Stock, which,
if such Right had been exercised immediately prior to such date and at a time
when the Series AA Preferred Stock transfer books of the Company were open, such
holder would have owned upon such exercise and been entitled to receive by
virtue of such dividend, subdivision, combination or reclassification, provided,
however, that in no event shall the consideration to be paid upon the exercise
of one Right be less than the aggregate par value of the shares of capital stock
of the Company issuable upon exercise of one Right.

          (b) (i)  In the event any Person becomes an Acquiring Person ("Flip-in
Event"), then proper provision shall be made so that each holder of a Right,
subject to Section 7(e) and Section 24 hereof and except as provided below,
shall after the later of the occurrence of such event and the effective date of
an appropriate registration statement pursuant to Section 9 hereof, have a right
to receive, upon exercise thereof at the then current Purchase Price, multiplied
by the then number of one one-hundredths of a share of Series AA Preferred Stock
for which a Right is then exercisable, in accordance with the terms of this
Rights Agreement, in lieu of shares of Series AA Preferred Stock, such number of
shares of Common Stock of the Company as shall equal the result obtained by (y)
multiplying the then current Purchase Price by the then number of one one-
hundredths of a share of Series AA Preferred Stock for which a Right is then
exercisable and dividing that product by (z) 50% of the current market price per
one share of Common Stock (determined pursuant to Section 11(f) hereof on the
date of the occurrence of the Flip-in Event) (such shares being referred to as
the "Adjustment Shares").

              (ii) A Flip-in Event shall not be deemed to have occurred as a
result of any Person becoming an Acquiring Person through a purchase of Common
Stock pursuant to a tender offer made in the manner prescribed by Section 14(d)
of the Exchange Act and the rules and regulations promulgated thereunder;
provided, however, that such tender offer shall provide for the acquisition of
all of the outstanding Common Stock held by any Person other than such Person
and its Affiliates or Associates at a price and on terms determined by a
majority of the members of the Board of Directors who are not officers of the
Company and who are not representatives, nominees, Affiliates or Associates of
an Acquiring Person, after receiving advice from one or more investment or
financial advisers, to be (A) fair to shareholders (taking into account all
factors which such members of the Board deem relevant) and (B) otherwise in the

                                      -13-
<PAGE>

best interests of the Company and its shareholders, employees, customers and
communities in which the Company does business.

          (c) In the event that there shall not be sufficient shares of Common
Stock authorized but unissued to permit the exercise in full of the Rights in
accordance with the foregoing subparagraph (b), the Company shall: (i) determine
the excess of (1) the value of the Adjustment Shares issuable upon the exercise
of a Right (the "Current Value"), over (2) the Purchase Price (such excess being
hereinafter referred to as the "Spread"), and (ii) with respect to each Right,
make adequate provision to substitute for such unavailable Adjustment Shares
either (1) cash, (2) a reduction in the Purchase Price, (3) other equity
securities of the Company, including without limitation Series AA Preferred
Stock, (4) debt securities of the Company, (5) other assets or (6) any
combination of the foregoing, having, together with the Adjustment Shares issued
upon exercise of such Right, an aggregate value equal to the Current Value,
where such aggregate value has been determined by the Board of Directors of the
Company based upon the advice of a reputable investment banking firm selected by
the Board of Directors of the Company; provided, however, if, within 30 days
following the date of the occurrence of a Flip-in Event, the Company shall have
not made adequate provision to deliver value pursuant to clause (ii) above, then
the Company shall be obligated to deliver, upon the surrender for exercise of a
Right and without requiring payment of the Purchase Price, Common Stock (to the
extent shares of such Common Stock are available) and then, if necessary, cash
or Series AA Preferred Stock, which shares and/or cash have an aggregate value
equal to the Spread. If the Board of Directors of the Company shall determine in
good faith that it is likely that sufficient additional Common Stock could be
authorized for issuance upon exercise in full of the Rights, the 30-day period
set forth above may be extended to the extent necessary, but not more than 120
days following the date of the occurrence of the Flip-in Event in order that the
Company may seek shareholder approval for the authorization of such additional
shares (such period, as it may be extended, hereinafter referred to as the
"Substitution Period"). To the extent that the Company determines that action
needs to be taken pursuant to the first and/or second sentences of this Section
11(c), the Company (y) shall provide, subject to Section 7(e) hereof, that such
action shall apply uniformly to all outstanding Rights, and (z) may suspend the
exercisability of the Rights until the expiration of the Substitution Period in
order to seek any authorization of additional shares and/or to decide the
appropriate form of distribution to be made pursuant to such first sentence and
to determine the value thereof. In the event of any such suspension, the Company
shall issue a public announcement stating that the exercisability of the Rights
has been temporarily suspended, as well as a public announcement at such time as
the suspension is no longer in effect. For purposes of this Section 11(c), the
value of the Common Stock shall be the current per share market price (as
determined pursuant to Section 11(f) hereof) per share of Common Stock on the
date of the occurrence of the Flip-in Event.

          (d) If the Company shall fix a record date for the issuance of rights
or warrants to all holders of Series AA Preferred Stock entitling them (for a
period expiring within 90 calendar days after such record date) to subscribe for
or purchase Series AA Preferred Stock (or securities having the same or more
favorable rights, privileges and preferences as the Series AA Preferred Stock
("Equivalent Preferred Stock")) or securities convertible into Series AA

                                      -14-
<PAGE>

Preferred Stock or Equivalent Preferred Stock, at a price per share of Series AA
Preferred Stock or per share of Equivalent Preferred Stock or having a
conversion or exercise price per share, as the case may be, less than the
current market price (as defined in Section 11(f) hereof) per share of Series AA
Preferred Stock on such record date, the Purchase Price to be in effect after
such record date shall be determined by multiplying the Purchase Price in effect
immediately prior to such date by a fraction, the numerator of which shall be
the number of shares of Series AA Preferred Stock outstanding on such record
date plus the number of shares of Series AA Preferred Stock which the aggregate
offering price of the total number of shares of Series AA Preferred Stock or
Equivalent Preferred Stock to be offered (and/or the aggregate initial
conversion price of the convertible securities so to be offered) would purchase
at such current market price, and the denominator of which shall be the number
of shares of Series AA Preferred Stock outstanding on such record date plus the
number of additional shares of Series AA Preferred Stock and/or Equivalent
Preferred Stock to be offered for subscription or purchase (or into which the
convertible securities so to be offered are initially convertible). In case such
subscription price may be paid in a consideration, part or all of which shall be
in a form other than cash, the value of such consideration shall be as
determined in good faith by a majority of the Board of Directors, whose
determination shall be described in a statement filed with the Rights Agent.
Shares of Series AA Preferred Stock owned by or held for the account of the
Company shall not be deemed outstanding for the purpose of any such computation.
Such adjustment shall be made successively whenever such a record date is fixed;
and in the event that such rights or warrants are not so issued, the Purchase
Price shall be adjusted to be the Purchase Price which would then be in effect
if such record date had not been fixed.

          (e) If the Company shall fix a record date for the making of a
distribution to all holders of Series AA Preferred Stock (including any such
distribution made in connection with a consolidation or merger in which the
Company is the continuing or surviving corporation) of evidences of
indebtedness, cash (other than a regular periodic cash dividend out of earnings
or retained earnings of the Company), assets (other than a dividend payable in
Series AA Preferred Stock, but including any dividend payable in stock other
than Series AA Preferred Stock) or convertible securities, subscription rights
or warrants (excluding those referred to in Section 11(d) hereof), the Purchase
Price to be in effect after such record date shall be determined by multiplying
the Purchase Price in effect immediately prior to such record date by a
fraction, the numerator of which shall be the Current Market Price for one share
of Series AA Preferred Stock (as defined in Section 11(f) hereof) on such record
date less the fair market value (as determined in good faith by a majority of
the Board of Directors, whose determination shall be described in a statement
filed with the Rights Agent) of the portion of the assets or evidences of
indebtedness so to be distributed or of such convertible securities,
subscription rights or warrants applicable to one share of Series AA Preferred
Stock, and the denominator of which shall be such Current Market Price for one
share of Series AA Preferred Stock. Such adjustments shall be made successively
whenever such a record date is fixed; and in the event that such distribution is
not so made, the Purchase Price shall again be adjusted to be the Purchase Price
which would then be in effect if such record date had not been fixed.

                                      -15-
<PAGE>

          (f) (i)  For the purpose of any computation hereunder, the "current
market price" of any security (a "Security" for purposes of this Section
11(f)(i)) on any date shall be deemed to be the average of the daily closing
prices per share of such Security for the 20 consecutive Trading Days (as
hereinafter defined) immediately prior to but not including such date; provided,
however, that in the event that the current market price per share of such
Security is determined during a period following the announcement by the issuer
of such Security of (A) a dividend or distribution on such Security payable in
shares of such Security or securities convertible into shares of such Security
or (B) any subdivision, combination or reclassification of such Security, and
prior to the expiration of 20 Trading Days after but not including the ex-
dividend date for such dividend or distribution or the record date for such
subdivision, combination or reclassification, then, and in each such case, the
"current market price" shall be appropriately adjusted to reflect the current
market price per share equivalent of such Security. The closing price for each
day shall be the last sale price or, in case no such sale takes place on such
day, the average of the closing bid and asked prices, in either case as reported
in the principal consolidated transaction reporting system with respect to
securities listed or admitted to trading on the New York Stock Exchange or, if
the Security is not listed or admitted to trading on the New York Stock
Exchange, as reported in the principal consolidated transaction reporting system
with respect to securities listed or admitted to trading on the principal
national securities exchange on which the Security is listed or admitted to
trading or, if the Security is not listed or admitted to trading on any national
securities exchange, as reported by the National Association of Securities
Dealers, Inc. Automated Quotation System ("Nasdaq") National Market System, or
if the Security is not listed or admitted to trading on any national securities
exchange or included in the Nasdaq National Market System, the average of the
high bid and low asked prices in the over-the-counter market, as reported by
Nasdaq or such other system then in use, or, if on any such date the Security is
not quoted by any such organization, the average of the closing bid and asked
prices as furnished by a professional market maker making a market in the
Security selected by a majority of the Board of Directors. If on any such date
no market maker is making a market in the Security, the fair value of such
Security on such date as determined in good faith by a majority of the Board of
Directors shall be used. The term "Trading Day" shall mean a day on which the
principal national securities exchange on which the Security is listed or
admitted to trading is open for the transaction of business or, if the Security
is not listed or admitted to trading on any national securities exchange a day
on which the Nasdaq National Market System is open for the transaction of
business or, if the Security is not listed or admitted to trading on any
national securities exchange or included in the Nasdaq National Market System, a
Business Day. If the Security is not publicly held or not so listed or traded,
"current market price" shall mean the fair value as determined in good faith by
a majority of the Board of Directors, whose determination shall be described in
a statement filed with the Rights Agent and shall be conclusive for all
purposes.

              (ii) For the purpose of any computation hereunder, the "current
market price" per share (or one one-hundredth of a share) of Series AA Preferred
Stock shall be determined in the same manner as set forth above for the Common
Stock in clause (i) of this Section 11(f) (other than the last sentence
thereof). If the current market price per share (or one one-hundredth of a
share) of Series AA Preferred Stock cannot be determined in the manner

                                      -16-
<PAGE>

provided above or if the Series AA Preferred Stock is not publicly held or
listed or traded in a manner described in clause (i) of this Section 11(f), the
"current market price" per share of Series AA Preferred Stock shall be
conclusively deemed to be an amount equal to 100 (as such number may be
appropriately adjusted for such events as stock splits, stock dividends and
recapitalizations with respect to the Common Stock occurring after the date of
this Rights Agreement) multiplied by the current market price per share of the
Common Stock and the "current market price" per one one-hundredth of a share of
Series AA Preferred Stock shall be equal to the current market price per share
of the Common Stock (as appropriately adjusted). If neither the Common Stock nor
the Series AA Preferred Stock is publicly held or so listed or traded, "current
market price" per share shall mean the fair value per share as determined in
good faith by the Board of Directors, whose determination shall be described in
a statement filed with the Rights Agent and shall be conclusive for all
purposes.

          (g) No adjustment in the Purchase Price shall be required unless such
adjustment would require an increase or decrease of at least 1% in the Purchase
Price; provided, however, that any adjustments which by reason of this Section
11(g) are not required to be made shall be carried forward and taken into
account in any subsequent adjustment. All calculations under this Section 11
shall be made to the nearest cent or to the nearest ten thousandth of a share of
Common Stock or other share and one-millionth of a share of Series AA Preferred
Stock, as the case may be. Notwithstanding the first sentence of this Section
11(g), any adjustment required by this Section 11 shall be made no later than
the earlier of (i) three years from the date of the transaction which mandates
such adjustment or (ii) the Expiration Date.

          (h) In the event that at any time, as a result of an adjustment made
pursuant to Section 11(a) or (b) hereof, the holder of any Right shall be
entitled to receive upon exercise of such Right any shares of capital stock of
the Company other than shares of Series AA Preferred Stock, thereafter the
number of such other shares so receivable upon exercise of any Right shall be
subject to adjustment from time to time in a manner and on terms as nearly
equivalent as practicable to the provisions with respect to the shares contained
in Section 11 hereof and the provisions of Sections 7, 9, 10, 13 and 14 hereof
with respect to the shares of Series AA Preferred Stock shall apply on like
terms to any such other shares.

          (i) All Rights originally issued by the Company subsequent to any
adjustment made to the Purchase Price hereunder shall evidence the right to
purchase, at the adjusted Purchase Price, the number of one one-hundredths of a
share of Series AA Preferred Stock or other shares of capital stock of the
Company purchasable from time to time hereunder upon exercise of the Rights, all
subject to further adjustment of the Purchase Price.

          (j) Unless the Company shall have exercised its election as provided
in Section 11(k) hereof, upon each adjustment of the Purchase Price as a result
of the calculations made in Section 11(d) and (e) hereof, each Right outstanding
immediately prior to the making of such adjustment shall thereafter evidence the
right to purchase, at the adjusted Purchase Price, that number of one one-
hundredths of a share of Series AA Preferred Stock (calculated to the nearest
one-millionth) obtained by (i) multiplying (A) the number of one one-hundredths
of a

                                      -17-
<PAGE>

share of Series AA Preferred Stock covered by a Right immediately prior to the
adjustment by (B) the Purchase Price in effect immediately prior to such
adjustment of the Purchase Price and (ii) dividing the product so obtained by
the Purchase Price in effect immediately after such adjustment of the Purchase
Price.

          (k) The Company may elect on or after the date of any adjustment of
the Purchase Price to adjust the number of Rights, in substitution for any
adjustment in the number of shares of Series AA Preferred Stock purchasable upon
the exercise of a Right. Each of the Rights outstanding after such adjustment of
the number of Rights shall be exercisable for the number of one one-hundredths
of a share of Series AA Preferred Stock for which such Right was exercisable
immediately prior to such adjustment. Each Right held of record prior to such
adjustment of the number of Rights shall become that number of Rights
(calculated to the nearest one ten- thousandth) obtained by dividing the
Purchase Price in effect immediately prior to adjustment of the Purchase Price
by the Purchase Price in effect immediately after adjustment of the Purchase
Price. The Company shall make a public announcement (with prompt notice thereof
to the Rights Agent) of its election to adjust the number of Rights, indicating
the record date for the adjustment, and, if known at the time, the amount of the
adjustment to be made. This record date may be the date on which the Purchase
Price is adjusted or any day thereafter, but, if the Right Certificates have
been issued, shall be at least 10 days later than the date of the public
announcement. If Right Certificates have been issued, upon each adjustment of
the number of Rights pursuant to this Section 11(k), the Company shall, as
promptly as practicable, cause to be distributed to holders of record of Right
Certificates on such record date Right Certificates evidencing, subject to
Section 14 hereof, the additional Rights to which such holders shall be entitled
as a result of such adjustment, or, at the option of the Company, shall cause to
be distributed to such holders of record in substitution and replacement for the
Right Certificates held by such holders prior to the date of adjustment, and
upon surrender thereof, if required by the Company, new Right Certificates
evidencing all the Rights to which such holders shall be entitled after such
adjustment. Right Certificates so to be distributed shall be issued, executed
and countersigned in the manner provided for herein (and may bear, at the option
of the Company, the adjusted Purchase Price) and shall be registered in the
names of the holders of record of Right Certificates on the record date
specified in the public announcement.

          (l) Irrespective of any adjustment or change in the Purchase Price or
the number of shares of Series AA Preferred Stock issuable upon the exercise of
the Rights, the Right Certificates theretofore and thereafter issued may
continue to express the Purchase Price and the number of shares which were
expressed in the initial Right Certificates issued hereunder.

          (m) Before taking any action that would cause an adjustment reducing
the Purchase Price below the then par value, if any, of the shares of Common
Stock or other securities and below one one-hundredth of the then par value, if
any, of the Series AA Preferred Stock, issuable upon exercise of the Rights, the
Company shall take any corporate action which may, in the opinion of its
counsel, be necessary in order that the Company may validly and legally issue
fully paid and nonassessable shares of such Series AA Preferred Stock, Common
Stock or other securities at such adjusted Purchase Price. If upon any exercise
of the Rights, a

                                      -18-
<PAGE>

holder is to receive a combination of Common Stock and common stock equivalents,
a portion of the consideration paid upon such exercise, equal to at least the
then par value of a share of Common Stock of the Company, shall be allocated as
the payment for each share of Common Stock of the Company so received.

          (n) In any case in which this Section 11 shall require that an
adjustment in the Purchase Price be made effective as of a record date for a
specified event, the Company may elect to defer (with prompt notice thereof to
the Rights Agent) until the occurrence of such event the issuing to the holder
of any Right exercised after such record date the shares of Series AA Preferred
Stock and other capital stock or securities of the Company, if any, issuable
upon such exercise over and above the shares of Series AA Preferred Stock and
other capital stock or securities of the Company, if any, issuable upon such
exercise on the basis of the Purchase Price in effect prior to such adjustment;
provided, however, that the Company shall deliver to such holder a due bill or
other appropriate instrument evidencing such holder's right to receive such
additional shares upon the occurrence of the event requiring such adjustment.

          (o) Anything in this Section 11 to the contrary notwithstanding, the
Company shall be entitled to make such reductions in the Purchase Price, in
addition to those adjustments expressly required by this Section 11, as and to
the extent that in their good faith judgment a majority of the Board of
Directors shall determine to be advisable in order that any (i) consolidation or
subdivision of the Series AA Preferred Stock, (ii) issuance wholly for cash of
any Series AA Preferred Stock at less than the then current market price, (iii)
issuance wholly for cash of Series AA Preferred Stock or securities which by
their terms are convertible into or exchangeable for Series AA Preferred Stock,
(iv) dividends on Series AA Preferred Stock payable in Series AA Preferred Stock
or (v) issuance of rights, options or warrants referred to hereinabove in this
Section 11, hereafter made by the Company to the holders of its Series AA
Preferred Stock, shall not be taxable to such stockholders.

          (p) In the event that at any time after the date of this Rights
Agreement and prior to the Distribution Date, the Company shall (i) declare or
pay any dividend on the Common Stock payable in shares of Common Stock or (ii)
effect a subdivision, combination or consolidation of the Common Stock (by
reclassification or otherwise than by payment of dividends in shares of Common
Stock) into a greater or lesser number of shares of Common Stock, then in any
such case (y) the number of one one-hundredths of a share of Series AA Preferred
Stock purchasable after such event upon proper exercise of each Right shall be
determined by multiplying the number of one one-hundredths of a share of Series
AA Preferred Stock so purchasable immediately prior to such event by a fraction,
the numerator of which is the number of shares of Common Stock outstanding
immediately before such event and the denominator of which is the number of
shares of Common Stock outstanding immediately after such event, and (z) each
share of Common Stock outstanding immediately after such event shall have issued
with respect to it that number of Rights which each share of Common Stock
outstanding immediately prior to such event had issued with respect to it. The
adjustments provided for in this Section 11(p) shall be made successively
whenever such a dividend is declared or paid or such a subdivision, combination
or consolidation is effected.

                                      -19-
<PAGE>

          (q) The Company covenants and agrees that it shall not, at any time
after the Distribution Date, (i) consolidate with or merge with or into, or
enter into a statutory share exchange with, any other Person (other than a
Subsidiary of the Company in a transaction that complies with Section 11(r)),
(ii) permit or cause any Person to consolidate with the Company, or merge with
and into the Company (other than a Subsidiary of the Company in a transaction
that complies with Section 11(r)), or (iii) sell or otherwise transfer (or
permit any Subsidiary to sell or transfer), in one or more transactions, assets
or earning power aggregating 50% or more of the assets or earning power of the
Company and its Subsidiaries (taken as a whole) to any other Person or Persons
(other than the Company and/or any of its Subsidiaries in one or more
transactions, each of which complies with Section 11(r)), if at the time of or
immediately after such consolidation, merger, exchange or sale there are any
rights, warrants or other instruments or securities outstanding or agreements in
effect which would substantially diminish or otherwise eliminate the benefits
intended to be afforded by the Rights.

          (r) The Company covenants and agrees that, after the Distribution
Date, it will not, except as permitted by Sections 23, 24 and 27 hereof, take
(or permit any Subsidiary of the Company to take) any action the purpose or
effect of which is to diminish substantially or otherwise eliminate the benefits
intended to be afforded by the Rights.

      12. Certificate of Adjusted Purchase Price or Number of Shares.  Whenever
          ----------------------------------------------------------
an adjustment is made as provided in Sections 11 or 13 hereof, the Company shall
(a) promptly prepare a certificate setting forth such adjustment, and a brief
statement of the facts and computations accounting for such adjustment, (b)
promptly file with the Rights Agent and with each transfer agent for the Series
AA Preferred Stock and the Common Stock a copy of such certificate and (c)
include a brief summary thereof in a mailing to each holder of a Right
Certificate in accordance with Section 26 hereof, or prior to the Distribution
Date, disclose a brief summary in a filing under the Exchange Act. The Rights
Agent shall be fully protected in relying on any such certificate and on any
adjustment therein contained and shall have no duty with respect to and shall
not be deemed to have knowledge of any adjustment unless and until it shall have
received such a certificate.

      13. Consolidation, Merger or Sale or Transfer of Assets or Earning Power.
          --------------------------------------------------------------------

          (a) In the event that, directly or indirectly, at any time after the
Distribution Date, (x) the Company shall consolidate with, merge with and into
or enter into a statutory share exchange with any other Person, (y) any Person
shall consolidate with or merge with and into the Company, and the Company shall
be the continuing or surviving corporation of such merger and, in connection
with such merger, all or part of the Common Stock shall be changed into or
exchanged for stock or other securities of any other Person (or the Company) or
cash or any other property, or (z) the Company shall sell, or otherwise transfer
(or one or more of its Subsidiaries shall sell or otherwise transfer), in one or
more transactions, assets or earning power aggregating 50% or more of the assets
or earning power of the Company and its Subsidiaries (taken as a whole) to any
other Person other than to the Company or one or more of its wholly owned
Subsidiaries (each of the events described in clauses (x), (y) and (z) of this
paragraph

                                      -20-
<PAGE>

being referred to herein as a "Flip-over Event"), then, and in each such case,
proper provision shall be made so that (i) each holder of a Right, subject to
Section 7(e) hereof, shall thereafter have the right to receive, upon the
exercise thereof at the then current Purchase Price multiplied by the then
number of one one-hundredths of a share of Series AA Preferred Stock for which a
Right is then exercisable in accordance with the terms of this Rights Agreement,
in lieu of Series AA Preferred Stock, such number of shares of freely tradable
Common Stock of the Principal Party (as hereinafter defined), free and clear of
liens, rights of call or first refusal, encumbrances or other adverse claims, as
shall be equal to the result obtained by (A) multiplying the then current
Purchase Price by the number of one one-hundredths of a share of Series AA
Preferred Stock for which a Right is then exercisable and dividing that product
by (B) 50% of the then current market price per share of the Common Stock of
such Principal Party (determined in the manner described in Section 11(f)
hereof) on the date of consummation of such consolidation, merger, exchange,
sale or transfer; (ii) the Principal Party shall thereafter be liable for, and
shall assume, by virtue of such consolidation, merger, exchange, sale or
transfer, all the obligations and duties of the Company pursuant to this Rights
Agreement; (iii) the term "Company" shall thereafter be deemed to refer to such
Principal Party, it being specifically intended that the provisions of Section
11 hereof, except for the provisions of 11(b), shall apply to such Principal
Party after the first occurrence of a Flip-over Event; and (iv) such Principal
Party shall take such steps (including, but not limited to, the authorization
and reservation of a sufficient number of shares of its Common Stock to permit
exercise of all outstanding Rights in accordance with this Section 13(a)) in
connection with such consummation as may be necessary to assure that the
provisions hereof shall thereafter be applicable, as nearly as reasonably may
be, in relation to the shares of its Common Stock thereafter deliverable upon
the exercise of the Rights.

          (b)  "Principal Party" shall mean:

               (i)  in the case of any transaction described in clause (x) or
(y) of the first sentence of Section 13(a) hereof, the Person that is the issuer
of any securities into which shares of Common Stock of the Company are converted
in such merger or consolidation, or for which shares of Common Stock of the
Company are exchanged, and if no securities are so issued, the Person, including
the Company, that is the other party to the merger, consolidation or share
exchange; and

               (ii) in the case of any transaction described in clause (z) of
the first sentence of Section 13(a) hereof, the Person that is the party
receiving the greatest portion of the assets or earning power transferred
pursuant to such transaction or transactions; provided, however, that in any
case described in clause (i) or (ii) in this Section 13(b), (x) if the Common
Stock of such Person is not at such time and has not been continuously over the
preceding 12-month period registered under Section 12 of the Exchange Act, and
such Person is a direct or indirect Subsidiary or Affiliate of another Person,
"Principal Party" shall refer to such other Person; (y) in case such Person is a
Subsidiary, directly or indirectly, or Affiliate of more than one Person, the
Common Stocks of all of which are and have been so registered, "Principal Party"
shall refer to whichever of such Persons is the issuer of the Common Stock
having the greatest aggregate current market price, and (z) in case such Person
is, or is owned directly or

                                      -21-
<PAGE>

indirectly by, a partnership or joint venture formed by two or more Persons that
are not owned, directly or indirectly, by the same Person, the rules set forth
in (x) and (y) above shall apply to each of the chains of ownership having an
interest in such joint venture as if such party were a "Subsidiary" of both or
all of such joint venturers and the Principal Parties in each such chain shall
bear the obligations set forth in this Section 13 in the same ratio as their
direct or indirect interests in such Person bear to the total of such interests.

          (c) The Company shall not consummate any such consolidation, merger,
exchange, sale or transfer unless the Principal Party shall have a sufficient
number of shares of its authorized Common Stock which have not been issued or
reserved for issuance to permit the exercise in full of the Rights in accordance
with this Section 13 and unless prior thereto the Company and each Principal
Party and each other Person who may become a Principal Party as a result of such
consolidation, merger, exchange, sale or transfer shall have executed and
delivered to the Rights Agent a supplemental agreement providing for the terms
set forth in paragraphs (a) and (b) of this Section 13 and further providing
that, as soon as practicable after the date of any consolidation, merger,
exchange, sale or transfer of assets mentioned in paragraph (a) of this Section
13, the Principal Party will:

              (i)   prepare and file a registration statement under the
Securities Act with respect to the Rights and the securities purchasable upon
exercise of the Rights on an appropriate form, use its best efforts to cause
such registration statement to become effective as soon as practicable after
such filing and use its best efforts to cause such registration statement to
remain effective (with a prospectus at all times meeting the requirements of the
Securities Act) until the Expiration Date;

              (ii)  use its best efforts to qualify or register the Rights and
the securities purchasable upon exercise of the Rights under the "blue sky" laws
of such jurisdictions as may be necessary or appropriate; and

              (iii) deliver to holders of the Rights historical financial
statements for the Principal Party and each of its Affiliates which comply in
all respects with the requirements for registration on Form 10 under the
Exchange Act.

      The provisions of this Section 13 shall similarly apply to successive
mergers or consolidations or sales or other transfers. In the event that a Flip-
over Event shall occur at any time after the occurrence of a Flip-in Event, the
Rights which have not theretofore been exercised shall thereafter also become
exercisable in the manner described in Section 13(a) hereof.

          (d) Notwithstanding anything in this Agreement to the contrary, this
Section 13 shall not be applicable to a transaction described in Section
13(a)(x), (y) or (z) if: (i) such transaction is consummated with a Person or
Persons who acquired Common Stock pursuant to a tender offer described in
Section 11(b)(ii) (or with a wholly owned Subsidiary of any such Person or
Persons), (ii) the price per share of Common Stock offered in such transaction
is not

                                      -22-
<PAGE>

less than the price per share of Common Stock paid to all holders of Common
Stock whose shares were purchased pursuant to such tender or exchange offer, and
(iii) the form of consideration being offered to the remaining holders of Common
Stock pursuant to such transaction is the same as the form of consideration paid
pursuant to such tender offer. Upon consummation of any transaction contemplated
by this Section 13(d), all Rights shall expire.

     14.  Fractional Rights and Fractional Shares.
          ---------------------------------------

          (a)  The Company shall not be required to issue fractions of Rights or
to distribute Right Certificates which evidence fractional Rights. In lieu of
such fractional Rights, there shall be paid to the registered holders of the
Right Certificates with regard to which such fractional Rights would otherwise
be issuable, an amount in cash equal to the same fraction of the current market
value of a whole Right. For the purposes of this Section 14(a), the current
market value of a whole Right shall be the closing price of the Rights for the
Trading Day immediately prior to the date on which such fractional Rights would
have been otherwise issuable. The closing price for any day shall be the last
sale price or, in case no such sale takes place on such day, the average of the
closing bid and asked prices, in either case as reported in the principal
consolidated transaction reporting system with respect to securities listed or
admitted to trading on the New York Stock Exchange or, if the Rights are not
listed or admitted to trading on the New York Stock Exchange, as reported in the
principal consolidated transaction reporting system with respect to securities
listed or admitted to trading on the principal national securities exchange on
which the Rights are listed or admitted to trading or, if the Rights are not
listed or admitted to trading on any national securities exchange, as reported
by the Nasdaq National Market System or, if the Rights are not listed or
admitted to trading on any national securities exchange or included in the
Nasdaq National Market System, the last quoted price, or, if not so quoted, the
average of the high bid and low asked prices in the over-the-counter market, as
reported by Nasdaq or such other system then in use or, if on any such date the
Rights are not quoted by any such organization, the average of the closing bid
and asked prices as furnished by a professional market maker making a market in
the Rights selected by a majority of the Board of Directors. If on any such date
no such market maker is making a market in the Rights, the fair value of the
Rights on such date as determined in good faith by a majority of the Board of
Directors shall be used.

          (b)  The Company shall not be required to issue fractions of shares of
Series AA Preferred Stock (other than fractions which are integral multiples of
one one-hundredth of a share of Series AA Preferred Stock) upon exercise of the
Rights or to distribute certificates which evidence fractional shares of Series
AA Preferred Stock (other than fractions which are integral multiples of one
one-hundredth of a share of Series AA Preferred Stock). Fractions of shares of
Series AA Preferred Stock in integral multiples of one one-hundredth of a share
of Series AA Preferred Stock may, at the election of the Company, be evidenced
by depositary receipts, pursuant to an appropriate agreement between the Company
and a depositary selected by it, provided that such agreement shall provide that
the holders of such depositary receipts shall have all the rights, privileges
and preferences to which they are entitled as beneficial owners of the shares of
Series AA Preferred Stock represented by such depositary receipts. In

                                      -23-
<PAGE>

lieu of fractional shares of Series AA Preferred Stock that are not integral
multiples of one one-hundredth of a share of Series AA Preferred Stock, the
Company may pay to the registered holders of Right Certificates at the time such
Right Certificates are exercised as herein provided an amount in cash equal to
the same fraction of the current market value of one one-hundredths of a share
of Series AA Preferred Stock. For purposes of this Section 14(b), the current
market value of one one-hundredth of a share of Series AA Preferred Stock shall
be one one-hundredth of the closing price of a share of Series AA Preferred
Stock (as determined pursuant to Section 11(f)(ii) hereof) for the Trading Day
immediately prior to the date of such exercise.

          (c)  Following the occurrence of one of the transactions or events
specified in Section 11 hereof giving rise to the right to receive common stock
equivalents (other than Series AA Preferred Stock) or other securities upon the
exercise of a Right, the Company shall not be required to issue fractions of
shares or units of such common stock equivalents or other securities upon
exercise of the Rights or to distribute certificates which evidence fractional
shares of such common stock equivalents or other securities. In lieu of
fractional shares or units of such common stock equivalents or other securities,
the Company may pay to the registered holders of Right Certificates at the time
such Rights are exercised as herein provided an amount in cash equal to the same
fraction of the current market value of a share or unit of such common stock
equivalent or other securities. For purposes of this Section 14(c), the current
market value shall be determined in the manner set forth in Section 11(f) hereof
for the Trading Day immediately prior to the date of such exercise and, if such
common stock equivalent is not traded, each such common stock equivalent shall
have the value of one one-hundredth of a share of Series AA Preferred Stock.

          (d)  Except as otherwise expressly provided in this Section 14, the
holder of a Right by the acceptance of the Right expressly waives such holder's
right to receive any fractional Rights or any fractional share upon exercise of
Rights.

     15.  Rights of Action.  All rights of action in respect of this Rights
          ----------------
Agreement, except for rights of action given to the Rights Agent under Section
18 or Section 20 hereof, are vested in the respective registered holders of the
Right Certificates (and, prior to the Distribution Date, the registered holders
of Common Stock); and any registered holder of any Right Certificate (or, prior
to the Distribution Date, of the Common Stock), without the consent of the
Rights Agent or of the holder of any other Right Certificate (or, prior to the
Distribution Date, of the Common Stock), may, in such holder's own behalf and
for such holder's own benefit, enforce, and may institute and maintain any suit,
action or proceeding against the Company to enforce, or otherwise act in respect
of, such holder's right to exercise the Rights evidenced by such Right
Certificate in the manner provided in such Right Certificate and in this Rights
Agreement. Without limiting the foregoing or any remedies available to the
holders of Rights, it is specifically acknowledged that the holders of Rights
would not have an adequate remedy at law for any breach of this Rights Agreement
and will be entitled to specific performance of the obligations under, and
injunctive relief against actual or threatened violations of, the obligations of
any Person subject to this Rights Agreement. Holders of Rights shall be entitled
to recover

                                      -24-
<PAGE>

from the Company the reasonable costs and expenses, including attorneys' fees,
incurred by them in any action to enforce the provisions of this Rights
Agreement.

     16.  Agreement of Right Holders.  Every holder of a Right by accepting the
          --------------------------
same consents and agrees with the Company and the Rights Agent and with every
other holder of a Right that:

          (a)  Prior to the Distribution Date, the Rights will be transferable
only in connection with the transfer of Common Stock;

          (b)  After the Distribution Date, the Right Certificates are
transferable only on the registry books of the Rights Agent if surrendered at
the stockholder services office of the Rights Agent or such office designated
for such purpose, duly endorsed or accompanied by a proper instrument of
transfer; and

          (c)  The Company and the Rights Agent may deem and treat the Person in
whose name the Right Certificate (or, prior to the Distribution Date, the
associated Common Stock Certificate) is registered as the absolute owner thereof
and of the Rights evidenced thereby (notwithstanding any notations of ownership
or writing on the Right Certificate or the associated Common Stock certificate
made by anyone other than the Company or the Rights Agent) for all purposes
whatsoever, and neither the Company nor the Rights Agent shall be affected by
any notice to the contrary.

     17.  Right Certificate Holder Not Deemed a Stockholder.  No holder, as
          -------------------------------------------------
such, of any Right Certificate shall be entitled to vote, receive dividends or
be deemed for any purpose the holder of Series AA Preferred Stock, Common Stock
or any other securities of the Company which may at any time be issuable on the
exercise of the Rights represented thereby, nor shall anything contained herein
or in any Right Certificate be construed to confer upon the holder of any Right
Certificate, as such, any of the rights of a stockholder of the Company or any
right to vote for the election of directors or upon any matter submitted to
stockholders at any meeting thereof, or to give or withhold consent to any
corporate action, or to receive notice of meetings or other actions affecting
stockholders (except as provided in Section 25 hereof), or to receive dividends
or subscription rights, or otherwise, until the Right or Rights evidenced by
such Right Certificate shall have been exercised in accordance with the
provisions hereof.

     18.  Concerning the Rights Agent.
          ---------------------------

          (a) The Company agrees to pay to the Rights Agent reasonable
compensation for all services rendered by it hereunder and, from time to time,
on demand of the Rights Agent, its reasonable expenses and counsel fees and
other disbursements incurred in the preparation, execution, delivery and
amendment of this Rights Agreement and the exercise and performance of its
duties hereunder.  The Company also agrees to indemnify the Rights Agent for,
and to hold it harmless against, any loss, liability, damage, judgment, fine,
penalty, claim, demand, settlement, cost or expense, incurred without gross
negligence, bad faith or willful misconduct

                                      -25-
<PAGE>

on the part of the Rights Agent (each as determined by a court of competent
jurisdiction), for any action taken, suffered or omitted by the Rights Agent in
connection with the acceptance and administration of this Rights Agreement,
including the costs and expenses of defending against any claim of liability.
Anything to the contrary notwithstanding, in no event shall the Rights Agent be
liable for special, indirect, consequential or incidental loss or damage of any
kind whatsoever (including but not limited to lost profits), even if the Rights
Agent has been advised of the likelihood of such loss or damage. Any liability
of the Rights Agent under this Rights Agreement will be limited to the amount of
fees paid by the Company to the Rights Agent.

          (b)  The Rights Agent shall be authorized and protected and shall
incur no liability for or in respect of any action taken, suffered or omitted by
it in connection with its acceptance and administration of this Rights Agreement
in reliance upon any Right Certificate or certificate for Series AA Preferred
Stock, Common Stock or for other securities of the Company, instrument of
assignment or transfer, power of attorney, endorsement, affidavit, letter,
notice, direction, consent, certificate, statement, or other paper or document
believed by it to be genuine and to be signed, executed and, where necessary,
verified or acknowledged, by the proper Person or Persons.

     19.  Merger or Consolidation or Change of Name of Rights Agent.
          ---------------------------------------------------------

          (a)  Any Person into which the Rights Agent or any successor Rights
Agent may be merged or with which it may be consolidated, or any Person
resulting from any merger or consolidation to which the Rights Agent or any
successor Rights Agent shall be a party, or any Person succeeding to the
corporate trust powers or business or the stock transfer business of the Rights
Agent or any successor Rights Agent, shall be the successor to the Rights Agent
under this Rights Agreement without the execution or filing of any paper or any
further act on the part of any of the parties hereto, provided that such Person
would be eligible for appointment as a successor Rights Agent under the
provisions of Section 21 hereof. In case at the time such successor Rights Agent
shall succeed to the agency created by this Rights Agreement, any of the Right
Certificates shall have been countersigned but not delivered, any such successor
Rights Agent may adopt the countersignature of the predecessor Rights Agent and
deliver such Right Certificates so countersigned; and in case at that time any
of the Right Certificates shall not have been countersigned, any successor
Rights Agent may countersign such Right Certificates either in the name of the
predecessor Rights Agent or in the name of the successor Rights Agent; and in
all such cases such Right Certificates shall have the full force provided in the
Right Certificates and in this Rights Agreement.

          (b)  In case at any time the name of the Rights Agent shall be changed
and at such time any of the Right Certificates shall have been countersigned but
not delivered, the Rights Agent may adopt the countersignature under its prior
name and deliver Right Certificates so countersigned; and in case at that time
any of the Right Certificates shall not have been countersigned, the Rights
Agent may countersign such Right Certificates either in its prior name or in its
changed name; and in all such cases such Right Certificates shall have the full
force provided in the Right Certificates and in this Rights Agreement.

                                      -26-
<PAGE>

     20.  Duties of Rights Agent.  The Rights Agent undertakes the duties and
          ----------------------
obligations imposed by this Rights Agreement upon the following terms and
conditions, by all of which the Company and the holders of Right Certificates,
by their acceptance thereof, shall be bound:

          (a)  The Rights Agent may consult with legal counsel (who may be legal
counsel for the Company), and the advice or opinion of such counsel shall be
full and complete authorization and protection to the Rights Agent and the
Rights Agent shall incur no liability for or in respect of any action taken,
suffered or omitted by it in good faith and in accordance with such advice or
opinion.

          (b)  Whenever in the performance of its duties under this Rights
Agreement the Rights Agent shall deem it necessary or desirable that any fact or
matter (including, without limitation, the identity of any Acquiring Person and
the determination of current market price) be proved or established by the
Company prior to taking or suffering any action hereunder, such fact or matter
(unless other evidence in respect thereof be herein specifically prescribed) may
be deemed to be conclusively proved and established by a certificate signed by
the Chairman of the Board, Chief Executive Officer, President, Chief Financial
Officer or any Vice President and by the Treasurer or any Assistant Treasurer or
the Secretary or any Assistant Secretary of the Company and delivered to the
Rights Agent; and such certificate shall be full authorization and protection to
the Rights Agent and the Rights Agent shall incur no liability for or in respect
of any action taken or suffered in good faith by it under the provisions of this
Rights Agreement in reliance upon such certificate.

          (c)  The Rights Agent shall be liable hereunder only for its own gross
negligence, bad faith or willful misconduct.

          (d)  The Rights Agent shall not be liable for or by reason of any of
the statements of fact or recitals contained in this Rights Agreement or in the
Right Certificates (except its countersignature thereof) or be required to
verify the same, but all such statements and recitals are and shall be deemed to
have been made by the Company only.

          (e)  The Rights Agent shall not have any liability for or be under any
responsibility in respect of the validity of this Rights Agreement or the
execution and delivery hereof (except the due execution hereof by the Rights
Agent) or in respect of the validity or execution of any Right Certificate
(except its countersignature thereof); nor shall it be responsible for any
breach by the Company of any covenant or condition contained in this Rights
Agreement or in any Right Certificate; nor shall it be responsible for any
adjustment required under the provisions of Sections 11 or 13 hereof or
responsible for the manner, method or amount of any such adjustment or the
ascertaining of the existence of facts that would require any such adjustment
(except with respect to the exercise of Rights evidenced by Right Certificates
after actual notice to the Rights Agent of any such adjustment); nor shall it by
any act hereunder be deemed to make any representation or warranty as to the
authorization or reservation of any shares of Series AA Preferred Stock or other
securities to be issued pursuant to this Rights Agreement or any Right
Certificate or as to whether any shares of Series AA

                                      -27-
<PAGE>

Preferred Stock or other securities will, when issued, be validly authorized and
issued, fully paid and nonassessable.

          (f)  The Company agrees that it will perform, execute, acknowledge and
deliver or cause to be performed, executed, acknowledged and delivered all such
further and other acts, instruments and assurances as may reasonably be required
by the Rights Agent for the carrying out or performing by the Rights Agent of
the provisions of this Rights Agreement.

          (g)  The Rights Agent is hereby authorized and directed to accept
instructions with respect to the performance of its duties hereunder from the
Chairman of the Board, Chief Executive Officer, President, Chief Financial
Officer, any Vice President, the Secretary, any Assistant Secretary, the
Treasurer or any Assistant Treasurer of the Company, and to apply to such
officers for advice or instructions in connection with its duties, and it shall
not be liable for any action taken or suffered or omitted to be taken by it in
good faith in accordance with instructions of any such officer or for any delay
in acting while waiting for those instructions.

          (h)  The Rights Agent and any stockholder, director, affiliate
officer, employee, agent or representative of the Rights Agent may buy, sell or
deal in any of the Rights or other securities of the Company or become
pecuniarily interested in any transaction in which the Company may be
interested, or contract with or lend money to the Company or otherwise act as
fully and freely as though it were not the Rights Agent under this Rights
Agreement. Nothing herein shall preclude the Rights Agent from acting in any
other capacity for the Company or for any other Person.

          (i)  The Rights Agent may execute and exercise any of the rights or
powers hereby vested in it or perform any duty hereunder either itself or by or
through its attorneys or agents, and the Rights Agent shall not be answerable or
accountable for any act, default, neglect or misconduct of any such attorneys or
agents or for any loss to the Company resulting from any such act, default,
neglect or misconduct, provided that reasonable care was exercised in the
selection and continued employment thereof.

          (j)  No provision of this Rights Agreement shall require the Rights
Agent to expend or risk its own funds or otherwise incur any financial liability
in the performance of any of its duties hereunder or in the exercise of its
rights if there shall be reasonable grounds for believing that repayment of such
funds or adequate indemnification against such risk or liability is not
reasonably assured to it.

          (k)  If, with respect to any Rights Certificate surrendered to the
Rights Agent for exercise or transfer, the certificate attached to the form of
assignment or form of election to purchase, as the case may be, has either not
been completed or indicates an affirmative response to clause 1, clause 2
and/or, in the case of the certificate attached to the form of election to
purchase, clause 3 thereof, the Rights Agent shall not take any further action
with respect to such requested exercise of transfer without first consulting
with the Company.

                                      -28-
<PAGE>

     21.  Change of Rights Agent. The Rights Agent or any successor Rights Agent
          ----------------------
may resign and be discharged from its duties under this Rights Agreement upon 30
days' notice in writing mailed to the Company and to each transfer agent of the
Common Stock and Series AA Preferred Stock by registered or certified mail, and
to the holders of the Right Certificates by first-class mail. The Company may
remove the Rights Agent or any successor Rights Agent upon 30 days' notice in
writing, mailed to the Rights Agent or successor Rights Agent, as the case may
be, and to each transfer agent of the Common Stock and Series AA Preferred Stock
by registered or certified mail, and to the holders of the Right Certificates by
first-class mail or, prior to the Distribution Date, through any filing made by
the Company pursuant to the Exchange Act. If the Rights Agent shall resign or be
removed or shall otherwise become incapable of acting, the Company shall appoint
a successor to the Rights Agent. If the Company shall fail to make such
appointment within a period of 30 days after such removal or after it has been
notified in writing of such resignation or incapacity by the resigning or
incapacitated Rights Agent or by the holder of a Right Certificate (which holder
shall, with such notice, submit such holder's Right Certificate for inspection
by the Company), then the registered holder of any Right Certificate may apply
to any court of competent jurisdiction for the appointment of a new Rights
Agent. Any successor Rights Agent, whether appointed by the Company or by such a
court, shall be (a) a corporation or other entity organized and doing business
under the laws of the United States or of any state, in good standing, having an
office in the States of New York or Colorado, which is authorized under such
laws to exercise corporate trust or stock transfer powers and is subject to
supervision or examination by federal or state authority, or (b) an affiliate of
a corporation or other entity described in clause (a) of this sentence. After
appointment, the successor Rights Agent shall be vested with the same powers,
rights, duties and responsibilities as if it had been originally named as Rights
Agent without further act or deed; but the predecessor Rights Agent shall
deliver and transfer to the successor Rights Agent any property at the time held
by it hereunder, and execute and deliver any further assurance, conveyance, act
or deed necessary for the purpose. Not later than the effective date of any such
appointment the Company shall file notice thereof in writing with the
predecessor Rights Agent and each transfer agent of the Common Stock and Series
AA Preferred Stock, and mail a notice thereof in writing to the registered
holders of the Right Certificates or, prior to the Distribution Date, through
any filing made by the Company pursuant to the Securities Exchange Act of 1934,
as amended. Failure to give any notice provided for this Section 21, however, or
any defect therein, shall not affect the legality or validity of the resignation
or removal of the Rights Agent or the appointment of the successor Rights Agent,
as the case may be.

     22.  Issuance of New Right Certificates.
          ----------------------------------

          (a)  Notwithstanding any of the provisions of this Rights Agreement or
of the Rights to the contrary, the Company may, at its option, issue new Right
Certificates evidencing Rights in such form as may be approved by a majority of
the Board of Directors then in office to reflect any adjustment or change in the
Purchase Price and the number or kind or class of shares of stock or other
securities or property purchasable under the Right Certificates made in
accordance with the provisions of this Rights Agreement.

                                      -29-
<PAGE>

          (b)  In addition, in connection with the issuance or sale of Common
Stock following the Distribution Date and prior to the redemption, exchange or
expiration of the Rights, the Company (a) shall with respect to shares of Common
Stock so issued or sold pursuant to the exercise of stock options or under any
employee benefit plan or arrangement, or upon the exercise, conversion or
exchange of securities hereinafter issued by the Company, and (b) may, in any
other case, if deemed necessary or appropriate by the Board of Directors, issue
Right Certificates representing the appropriate number of Rights in connection
with such issuance or sale; provided, however, that (i) no such Right
Certificates shall be issued if, and to the extent that, the Company shall be
advised by counsel that such issuance would create a significant risk of
material adverse tax consequences to the Company or the Person to whom such
Right Certificates would be issued, and (ii) no Right Certificate shall be
issued if, and to the extent that, appropriate adjustment shall otherwise have
been made in lieu of the issuance thereof.

     23.  Redemption and Termination.
          --------------------------

          (a)  A majority of the Board of Directors then in office may, at its
option, at any time prior to the earlier of (i) the Close of Business on the
Stock Acquisition Date or (ii) the Close of Business on the Final Expiration
Date, elect to redeem all but not less than all of the then outstanding Rights
at a redemption price of $0.01 per Right, as appropriately adjusted to reflect
any stock split, stock dividend or similar transaction occurring after the date
hereof (such redemption price being hereinafter referred to as the "Redemption
Price"). The redemption of the Rights by the Board of Directors may be made
effective at such time, on such basis and with such conditions as the Board of
Directors in its sole discretion may establish.

          (b)  Immediately upon the action of a majority of the Board of
Directors then in office electing to redeem the Rights, evidence of which shall
be promptly filed with the Rights Agent, or, when appropriate, immediately upon
the time or satisfaction of such conditions as the Board of Directors may have
established, and without any further action and without any notice, the right to
exercise the Rights will terminate and the only right thereafter of the holders
of Rights shall be to receive the Redemption Price. The Company shall promptly
give public disclosure of any such redemption; provided, however, that the
failure to give, or any defect in, any such disclosure shall not affect the
validity of such redemption. Within 10 days after the action of the Board of
Directors ordering the redemption of the Rights, the Company shall give notice
of such redemption to the Rights Agent and to the holders of the then
outstanding Rights by mailing such notice to all such holders at their last
addresses as they appear upon the registry books of the Rights Agent or, prior
to the Distribution Date, on the registry books of the Transfer Agent for the
Common Stock. Any notice which is mailed in the manner herein provided shall be
deemed given, whether or not the holder receives the notice. Each such notice of
redemption will state the method by which the payment of the Redemption Price
will be made.

          (c)  Neither the Company nor any of its Affiliates or Associates may
redeem, acquire or purchase for value any Rights at any time in any manner other
than that specifically

                                      -30-
<PAGE>

set forth in this Section 23 or Section 24 hereof and other than in connection
with the purchase of Common Stock prior to the Distribution Date.

     24.  Exchange.
          --------

          (a)  The Board of Directors may, at its option, at any time after any
Person becomes an Acquiring Person, exchange all or part of the then outstanding
and exercisable Rights (which shall not include Rights that have become null and
void pursuant to the provisions of Section 7(e) hereof) for Common Stock at an
exchange ratio of one share of Common Stock per Right, appropriately adjusted to
reflect adjustments in the number of Rights pursuant to Section 11 of this
Rights Agreement (such exchange ratio being hereinafter referred to as the
"Exchange Ratio"). Notwithstanding the foregoing, the Board of Directors shall
not be empowered to effect such exchange at any time after any Person (other
than the Company, any Subsidiary of the Company, any employee benefit plan or
compensation arrangement of the Company or any such Subsidiary, or any entity
holding securities of the Company to the extent organized, appointed or
established by the Company or any such Subsidiary for or pursuant to the terms
of any such employee benefit plan or compensation arrangement), together with
all Affiliates and Associates of such Person, becomes the Beneficial Owner of
50% or more of the Voting Power of the Company.

          (b)  Immediately upon the action of the Board of Directors ordering
the exchange of any Rights pursuant to paragraph (a) of this Section 24 and
without any further action and without any notice, the right to exercise such
Rights shall terminate and the only rights thereafter of holders of such Rights
shall be to receive that number of shares of Common Stock equal to the number of
such Rights held by such holder multiplied by the Exchange Ratio. The Company
promptly shall give public notice of any such exchange (with prompt notice
thereof to the Rights Agent); provided, however, that the failure to give, or
any defect in, such notice shall not affect the validity of such exchange. The
Company promptly shall mail a notice of any such exchange to all of the holders
of such Rights at their last addresses as they appear upon the registry books of
the Rights Agent. Any notice which is mailed in the manner herein provided shall
be deemed given, whether or not the holder receives the notice. Each such notice
of exchange will state the method by which the exchange of Common Stock for
Rights will be effected and, in the event of any partial exchange, the number of
Rights which will be exchanged. Any partial exchange shall be effected pro rata
based on the number of Rights (other than Rights which have become void pursuant
to the provisions of Section 7(e) hereof) held by each holder of Rights.

          (c)  In any exchange pursuant to this Section 24, the Company, at its
option, may substitute Series AA Preferred Stock (or equivalent Series AA
Preferred stock, as such term is defined in Section 11(d) hereof) for Common
Stock exchangeable for Rights, at the initial rate of one one-hundredth of a
share of Series AA Preferred Stock (or equivalent Series AA Preferred stock) for
each share of Common Stock, as appropriately adjusted to reflect adjustments in
the voting rights of the Series AA Preferred Stock pursuant to the terms
thereof, so that the fraction

                                      -31-
<PAGE>

of a share of Series AA Preferred Stock delivered in lieu of each share of
Common Stock shall have the same voting rights as one share of Common Stock.

          (d)  In the event that there shall not be sufficient shares of Common
Stock or Series AA Preferred Stock (or equivalent Series AA Preferred stock)
authorized but unissued to permit any exchange of Rights as contemplated in
accordance with this Section 24, the Company shall take all such action as may
be necessary to authorize additional shares of Common Stock or Series AA
Preferred Stock (or equivalent Series AA Preferred stock) for issuance upon
exchange of the Rights.

          (e)  The Company shall not be required to issue fractions of Common
Stock or to distribute certificates which evidence fractional shares of Common
Stock. In lieu of such fractional shares of Common Stock, the Company shall pay
to the registered holders of the Right Certificates with regard to which such
fractional shares of Common Stock would otherwise be issuable an amount in cash
equal to the same fraction of the current market value of a whole share of
Common Stock. For the purposes of this paragraph (e), the current market value
of a whole share of Common Stock shall be the current market price of a share of
Common Stock (as determined pursuant to the second sentence of Section 11(f)(i)
hereof) for the Trading Day immediately prior to the date of exchange pursuant
to this Section 24.

     25.  Notice of Proposed Actions.
          --------------------------

          (a)  In case the Company shall propose at any time after the
Distribution Date (a) to pay any dividend payable in stock of any class to the
holders of the Series AA Preferred Stock or to make any other distribution to
the holders of the Series AA Preferred Stock (other than a regular periodic cash
dividend out of earnings or retained earnings of the Company), (b) to offer to
the holders of the Series AA Preferred Stock rights or warrants to subscribe for
or to purchase any additional shares of Series AA Preferred Stock or shares of
stock of any other class or any other securities, rights or options, (c) to
effect any reclassification of the Series AA Preferred Stock (other than a
reclassification involving only the subdivision of outstanding shares of Series
AA Preferred Stock), (d) to effect any consolidation or merger into or with, or
any statutory share exchange with, or to effect any sale or other transfer (or
to permit one or more of its Subsidiaries to effect any sales or other
transfer), in one or more transactions, of 50% or more of the assets or earning
power of the Company and its Subsidiaries (taken as a whole) to, any other
Person, (e) to effect the liquidation, dissolution or winding up of the Company,
or (f) to declare or pay any dividend on the Common Stock payable in Common
Stock or to effect a subdivision, combination or consolidation of the Common
Stock (by reclassification or otherwise than by payment of dividends in Common
Stock), then, in each such case, the Company shall give to each holder of a
Right and the Rights Agent, in accordance with Section 26 hereof, a notice of
such proposed action, which shall specify the record date for the purposes of
such stock dividend, distribution of rights or warrants, or the date on which
such reclassification, consolidation, merger, sale, transfer, liquidation,
dissolution, or winding up is to take place and the date of participation
therein by the holders of the Common Stock and/or Series AA Preferred Stock, if
any such date is to be fixed. Such notice shall be so given in the

                                      -32-
<PAGE>

case of any action covered by clauses (a) or (b) above at least ten days prior
to the record date for determining holders of the Series AA Preferred Stock for
purposes of such action, and in the case of any such other action, at least ten
days prior to the date of the taking of such proposed action or the date of
participation therein by the holders of Series AA Preferred Stock, whichever
shall be the earlier. The failure to give notice required by this Section 25 or
any defect therein shall not affect the legality or validity of the action taken
by the Company or the vote upon any such action.

          (b)  In case a Flip-in Event shall occur, then the Company shall as
soon as practicable thereafter give to each holder of a Right Certificate, in
accordance with Section 26 hereof, a notice of the occurrence of such event,
which shall specify the event and the consequences of the event to holders of
Rights under Section 11(b) hereof.

     26.  Notices.  Notices or demands authorized by this Rights Agreement to be
          -------
given or made by the Rights Agent or by the holder of any Right Certificate to
or on the Company shall be sufficiently given or made if sent by first-class
mail, postage prepaid, addressed (until another address is filed in writing with
the Rights Agent) as follows:

          Ribozyme Pharmaceuticals, Inc.
          2950 Wilderness Place
          Boulder, CO 80301
          Attention: Corporate Secretary

Subject to the provisions of Section 21 hereof, any notice or demand authorized
by this Rights Agreement to be given or made by the Company or by the holder of
any Right Certificate to or on the Rights Agent shall be sufficiently given or
made if sent by first-class mail, postage prepaid, addressed (until another
address is filed in writing with the Company) as follows:

          The American Stock Transfer & Trust Company
          40 Wall Street
          New York, NY 10005
          Attention: Wilbert Myles

Notices or demands authorized by this Rights Agreement to be given or made by
the Company or the Rights Agent to the holder of any Right Certificate (or prior
to the Distribution Date, any Common Stock) shall be sufficiently given or made
if sent by first-class mail, postage prepaid, addressed to such holder at the
address of such holder as shown on the registry books of the Company.

      27. Supplements and Amendments.  The Company may from time to time
          --------------------------
supplement or amend this Rights Agreement without the approval of any holders of
Right Certificates in order (a) to cure any ambiguity, (b) to correct or
supplement any provision contained herein which may be defective or inconsistent
with any other provisions herein, (c) to shorten or lengthen any time period
hereunder (including without limitation to extend the Final Expiration

                                     -33-
<PAGE>

Date), (d) increase or decrease the Purchase Price, or (e) to change or
supplement the provisions hereunder in any manner which the Company may deem
necessary or desirable; provided, however, that from and after such time as any
Person becomes an Acquiring Person, this Rights Agreement shall not be amended
in any manner which would adversely affect the interests of the holders of
Rights; provided further that this Rights Agreement may not be supplemented or
amended to lengthen pursuant to clause (c) of this sentence, (A) the time period
relating to the when the Rights may be redeemed at such time as the Rights are
not then redeemable, or (B) any other time period unless such lengthening is for
the purpose of protecting, enhancing or clarifying the rights of, and/or the
benefits to, the holders of the Rights; provided further that the Company shall
have the right to make unilaterally any changes necessary to facilitate the
appointment of a successor Rights Agent, which such changes shall be set forth
in a writing by the Company or by the Company and such successor Rights Agent.
Without limiting the foregoing, the Company may at any time prior to such time
as any Person becomes an Acquiring Person amend this Rights Agreement to lower
the thresholds set forth in Sections 1(a) and 3(a) hereof from 15% to not less
than the greater of (i) any percentage greater than the largest percentage of
the Voting Power of the Company then known by the Company to be beneficially
owned by any Person (other than the Company, any Subsidiary of the Company, or
any employee benefit plan or compensation arrangement of the Company or any
Subsidiary of the Company, and any entity holding securities of the Company to
the extent organized, appointed or established by the Company or any such
Subsidiary for or pursuant to the terms of any such employee benefit plan or
compensation arrangement) together with all Affiliates and Associates of such
Person and (ii) 10%. Upon the delivery of a certificate from an appropriate
officer of the Company which states that the proposed supplement or amendment is
in compliance with the terms of this Section 27 and such supplement or amendment
does not increase the Rights Agent's duties, liabilities or obligations, the
Rights Agent shall execute such supplement or amendment.

     28.  Successors. All the covenants and provisions of this Rights Agreement
          ----------
by or for the benefit of the Company or the Rights Agent shall bind and inure to
the benefit of their respective successors and assigns hereunder.

     29.  Benefits of This Rights Agreement. Nothing in this Rights Agreement
          ---------------------------------
shall be construed to give to any Person other than the Company, the Rights
Agent and the registered holders of the Right Certificates (and, prior to the
Distribution Date, the Common Stock) any legal or equitable right, remedy or
claim under this Rights Agreement; but this Rights Agreement shall be for the
sole and exclusive benefit of the Company, the Rights Agent and the registered
holders of the Right Certificates (and, prior to the Distribution Date, the
Common Stock).

     30.  Severability.  If any term, provision, covenant or restriction of this
          ------------
Rights Agreement is held by a court of competent jurisdiction or other authority
to be invalid, void or unenforceable, the remainder of the terms, provisions,
covenants and restrictions of this Rights Agreement shall remain in full force
and effect and shall in no way be affected, impaired or invalidated. It is the
intent of the parties hereto to enforce the remainder of the terms, provisions,
covenants and restrictions of this Rights Agreement to the maximum extent
permitted by law.

                                     -34-
<PAGE>

     31.  Governing Law.  This Rights Agreement and each Right Certificate
          -------------
issued hereunder shall be deemed to be a contract made under the laws of the
State of Colorado and for all purposes shall be governed by and construed in
accordance with the laws of such State applicable to contracts to be made and
performed entirely within such state.

     32.  Counterparts.  This Rights Agreement may be executed in any number of
          ------------
counterparts and each of such counterparts shall for all purposes be deemed to
be an original, and all such counterparts shall together constitute but one and
the same instrument.

     33.  Descriptive Headings.  Descriptive headings of the several Sections of
          --------------------
this Rights Agreement are inserted for convenience only and shall not control or
affect the meaning or construction of any of the provisions hereof.

                                     -35-
<PAGE>

          IN WITNESS WHEREOF, the parties hereto have caused this Rights
Agreement to be duly executed, all as of the day and year first above written.

                              RIBOZYME PHARMACEUTICAL, INC.

                              By: /s/ Ralph Christoffersen
                                 ------------------------------------
                              Name: Ralph E. Christoffersen
                                    ---------------------------------
                              Title: Chief Executive Officer
                                    ---------------------------------

                              AMERICAN STOCK TRANSFER & TRUST COMPANY

                              By: /s/ Wilbert Myles
                                 ------------------------------------
                              Name: Wilbert Myles
                                   ----------------------------------
                              Title: Vice President
                                    ---------------------------------

                                     -36-
<PAGE>

                                   EXHIBIT A

                                    FORM OF
                          CERTIFICATE OF DESIGNATION

                                      OF

                SERIES AA JUNIOR PARTICIPATING PREFERRED STOCK

                                      OF

                        RIBOZYME PHARMACEUTICALS, INC.

     Ribozyme Pharmaceuticals, Inc., a corporation organized and existing under
the General Corporation Law of the State of Delaware, in accordance with the
provisions of Section 103 thereof, DOES HEREBY CERTIFY:

That pursuant to the authority vested in the Board of Directors in accordance
with the provisions of the Certificate of Incorporation of the said Corporation,
the said Board of Directors on November 21, 2000 adopted the following
resolution creating a series of 200,000 shares of Preferred Stock designated as
"Series AA Junior Participating Preferred Stock":

          RESOLVED, that pursuant to the authority vested in the Board of
          Directors of this Corporation in accordance with the provisions of the
          Certificate of Incorporation, a series of Preferred Stock, par value
          $.01 per share, of the Corporation be and hereby is created, and that
          the designation and number of shares thereof and the voting and other
          powers, preferences and relative, participating, optional or other
          rights of the shares of such series and the qualifications,
          limitations and restrictions thereof are as follows:

1.   Designation and Amount. The shares of such series shall be designated as
     ----------------------
"Series AA Junior Participating Preferred Stock" (the "Series AA Preferred
Stock") and the number of shares constituting the Series AA Preferred Stock
shall be Two Hundred Thousand (200,000). Such number of shares may be increased
or decreased by resolution of the Board of Directors; provided that no decrease
shall reduce the number of shares of Series AA Preferred Stock to a number less
than the number of shares then outstanding plus the number of shares reserved
for issuance upon the exercise of outstanding options, rights or warrants or
upon the conversion of any outstanding securities issued by the Corporation
convertible into Series AA Preferred Stock.

2.   Dividends and Distributions.
     ---------------------------

          (A)  Subject to the rights of the holders of any shares of any series
of Series AA Preferred stock (or any similar stock) ranking prior and superior
to the Series AA Preferred Stock with respect to dividends, the holders of
shares of Series AA Preferred Stock, in

                                      A-1
<PAGE>

preference to the holders of shares of Common Stock, and of any other junior
stock, shall be entitled to receive, when, as and if declared by the Board of
Directors out of funds legally available for the purpose, quarterly dividends
payable in cash on any regular quarterly dividend payment date as shall be
established by the Board of Directors (each such date being referred to herein
as a "Quarterly Dividend Payment Date"), commencing on the first Quarterly
Dividend Payment Date after the first issuance of a share or fraction of a share
of Series AA Preferred Stock, in an amount per share (rounded to the nearest
cent) equal to the greater of (a) $1 or (b) subject to the provision for
adjustment hereinafter set forth, 100 times the aggregate per share amount of
all cash dividends, and 100 times the aggregate per share amount (payable in
kind) of all non-cash dividends or other distributions, other than a dividend
payable in shares of Common Stock or a subdivision of the outstanding shares of
Common Stock (by reclassification or otherwise), declared on the Common Stock
since the immediately preceding Quarterly Dividend Payment Date or, with respect
to the first Quarterly Dividend Payment Date, since the first issuance of any
share or fraction of a share of Series AA Preferred Stock. In the event the
Corporation shall at any time after November 22, 2000 (the "Rights Declaration
Date") declare or pay any dividend on the Common Stock payable in shares of
Common Stock, or effect a subdivision or combination or consolidation of the
outstanding shares of Common Stock (by reclassification or otherwise than by
payment of a dividend in shares of Common Stock) into a greater or lesser number
of shares of Common Stock, then in each such case the amount to which holders of
shares of Series AA Preferred Stock were entitled immediately prior to such
event under clause (b) of the preceding sentence shall be adjusted by
multiplying such amount by a fraction, the numerator of which is the number of
shares of Common Stock outstanding immediately after such event and the
denominator of which is the number of shares of Common Stock that were
outstanding immediately prior to such event.

          (B) The Corporation shall declare a dividend or distribution on the
Series AA Preferred Stock as provided in paragraph (A) of this Section
immediately after it declares a dividend or distribution on the Common Stock
(other than a dividend payable in shares of Common Stock); provided that, in the
event no dividend or distribution shall have been declared on the Common Stock
during the period between any Quarterly Dividend Payment Date and the next
subsequent Quarterly Dividend Payment Date, a dividend of $1 per share on the
Series AA Preferred Stock shall nevertheless be payable on such subsequent
Quarterly Dividend Payment Date.

          (C) Dividends shall begin to accrue and be cumulative on outstanding
shares of Series AA Preferred Stock from the Quarterly Dividend Payment Date
next preceding the date of issue of such shares, unless the date of issue of
such shares is prior to the record date for the first Quarterly Dividend Payment
Date, in which case dividends on such shares shall begin to accrue from the date
of issue of such shares, or unless the date of issue is a Quarterly Dividend
Payment Date or is a date after the record date for the determination of holders
of shares of Series AA Preferred Stock entitled to receive a quarterly dividend
and before such Quarterly Dividend Payment Date, in either of which events such
dividends shall begin to accrue and be cumulative from such Quarterly Dividend
Payment Date. Accrued but unpaid dividends shall not bear interest. Dividends
paid on the shares of Series AA Preferred Stock in an amount less than

                                      A-2
<PAGE>

the total amount of such dividends at the time accrued and payable on such
shares shall be allocated pro rata on a share-by-share basis among all such
shares at the time outstanding. The Board of Directors may, in accordance with
applicable law, fix a record date for the determination of holders of shares of
Series AA Preferred Stock entitled to receive payment of a dividend or
distribution declared thereon, which record date shall be not more than such
number of days prior to the date fixed for the payment thereof as may be allowed
by applicable law.

3.   Voting Rights.  The holders of shares of Series AA Preferred Stock shall
     -------------
have the following voting rights:

          (A) Each share of Series AA Preferred Stock shall entitle the holder
thereof to 100 votes on all matters submitted to a vote of the stockholders of
the Corporation.

          (B) Except as otherwise provided in the Corporation's Certificate of
Incorporation (as amended hereby), or by law, the holders of shares of Series AA
Preferred Stock, the holders of shares of Common Stock, and the holders of
shares of any other capital stock of the Corporation having general voting
rights, shall vote together as one class on all matters submitted to a vote of
stockholders of the Corporation.

          (a) Except as set forth in the Corporation's Certificate of
Incorporation (as amended hereby), and except as otherwise provided by law,
holders of Series AA Preferred Stock shall have no special voting rights and
their consent shall not be required (except to the extent they are entitled to
vote with holders of Common Stock as set forth herein) for taking any corporate
action.

4.   Certain Restrictions.
     --------------------

          (A) Whenever quarterly dividends or other dividends or distributions
payable on the Series AA Preferred Stock as provided in Section 2 are in
arrears, thereafter and until all accrued and unpaid dividends and
distributions, whether or not declared, on shares of Series AA Preferred Stock
outstanding shall have been paid in full, the Corporation shall not:

          (i)    declare or pay dividends, or make any other distributions, on
any shares of stock ranking junior (either as to dividends or upon liquidation,
dissolution or winding up) to the Series AA Preferred Stock;

          (ii)   declare or pay dividends, or make any other distributions, on
any shares of stock ranking on a parity (either as to dividends or upon
liquidation, dissolution or winding up) with the Series AA Preferred Stock,
except dividends paid ratably on the Series AA Preferred Stock and all such
parity stock on which dividends are payable or in arrears in proportion to the
total amounts to which the holders of all such shares are then entitled;

          (iii)  redeem or purchase or otherwise acquire for consideration
shares of any stock ranking junior (either as to dividends or upon liquidation,
dissolution or winding

                                      A-3
<PAGE>

up) to the Series AA Preferred Stock, provided that the Corporation may at any
time redeem, purchase or otherwise acquire shares of any such junior stock in
exchange for shares of any stock of the Corporation ranking junior (either as to
dividends or upon dissolution, liquidation or winding up) to the Series AA
Preferred Stock; or

              (iv)  redeem or purchase or otherwise acquire for consideration
any shares of Series AA Preferred Stock, or any shares of stock ranking on a
parity with the Series AA Preferred Stock, except in accordance with a purchase
offer made in writing or by publication (as determined by the Board of
Directors) to all holders of such shares upon such terms as the Board of
Directors, after consideration of the respective annual dividend rates and other
relative rights and preferences of the respective series and classes, shall
determine in good faith will result in fair and equitable treatment among the
respective series or classes.

          (b) The Corporation shall not permit any subsidiary of the Corporation
to purchase or otherwise acquire for consideration any shares of stock of the
Corporation unless the Corporation could, under paragraph (A) of this Section 4,
purchase or otherwise acquire such shares at such time and in such manner.

5.   Reacquired Shares.  Any shares of Series AA Preferred Stock purchased or
     -----------------
otherwise acquired by the Corporation in any manner whatsoever shall become
authorized but unissued shares of Series AA Preferred Stock and may be reissued
as part of a new series of Series AA Preferred Stock subject to the conditions
and restrictions on issuance set forth in the Articles of Incorporation, as
amended hereby, and by any subsequent amendments, or as otherwise required by
law.

6.   Liquidation, Dissolution or Winding Up.  Upon any liquidation, dissolution
     --------------------------------------
or winding up of the Corporation, no distribution shall be made (1) to the
holders of shares of stock ranking junior (either as to dividends or upon
liquidation, dissolution or winding up) to the Series AA Preferred Stock unless,
prior thereto, the holders of shares of Series AA Preferred Stock shall have
received $100.00 per share, plus an amount equal to accrued and unpaid dividends
and distributions thereon, whether or not declared, to the date of such payment,
provided that the holders of shares of Series AA Preferred Stock shall be
entitled to receive an aggregate amount per share, subject to the provision for
adjustment hereinafter set forth, equal to 100  times the aggregate amount to be
distributed per share to holders of shares of Common Stock, or (2) to the
holders of shares of stock ranking on a parity (either as to dividends or upon
liquidation, dissolution or winding up) with the Series AA Preferred Stock,
except distributions made ratably on the Series AA Preferred Stock and all such
parity stock in proportion to the total amounts to which the holders of all such
shares are entitled upon such liquidation, dissolution or winding up. In the
event the Corporation shall at any time after the Rights Declaration Date
declare or pay any dividend on the Common Stock payable in shares of Common
Stock, or effect a subdivision or combination or consolidation of the
outstanding shares of Common Stock (by reclassification or otherwise than by
payment of a dividend in shares of Common Stock) into a greater or lesser number
of shares of Common Stock, then in each such case the aggregate amount to which
holders of shares of Series AA Preferred Stock were entitled immediately prior
to such event

                                      A-4
<PAGE>

under the provision in clause (1) of the preceding sentence shall be adjusted by
multiplying such amount by a fraction, the numerator of which is the number of
shares of Common Stock outstanding immediately after such event and the
denominator of which is the number of shares of Common Stock that were
outstanding immediately prior to such event.

7.   Consolidation, Merger, Etc. In case the Corporation shall enter into any
     --------------------------
consolidation, merger, statutory share exchange, combination or other
transaction in which the shares of Common Stock are exchanged for or changed
into other stock or securities, cash and/or any other property, then in any such
case each share of Series AA Preferred Stock shall at the same time be similarly
exchanged or changed into an amount per share, subject to the provision for
adjustment hereinafter set forth, equal to 100 times the aggregate amount of
stock, securities, cash and/or any other property (payable in kind), as the case
may be, into which or for which each share of Common Stock is changed or
exchanged. In the event the Corporation shall at any time after the Rights
Declaration Date declare or pay any dividend on the Common Stock payable in
shares of Common Stock, or effect a subdivision or combination or consolidation
of the outstanding shares of Common Stock (by reclassification or otherwise than
by payment of a dividend in shares of Common Stock) into a greater or lesser
number of shares of Common Stock, then in each such case the amount set forth in
the preceding sentence with respect to the exchange or change of shares of
Series AA Preferred Stock shall be adjusted by multiplying such amount by a
fraction, the numerator of which is the number of shares of Common Stock
outstanding immediately after such event and the denominator of which is the
number of shares of Common Stock that are outstanding immediately prior to such
event.

8.   No Redemption.  The shares of Series AA Preferred Stock shall not be
     -------------
redeemable.

9.   Rank.  The Series AA Preferred Stock shall rank, with respect to the
     ----
payment of dividends and the distribution of assets, junior to all series of any
other class of the Corporation's Preferred Stock.

10.  Amendment. The Articles of Incorporation of the Corporation shall not be
     ---------
amended in any manner which would materially alter or change the powers,
preferences or special rights of the Series AA Preferred Stock so as to affect
them adversely without the affirmative vote of the holders of at least two-
thirds of the outstanding shares of Series AA Preferred Stock, voting together
as a single class.

11.  Fractional Shares.  Series AA Preferred Stock may be issued in fractions of
     -----------------
a share which shall entitle the holder, in proportion to such holder's
fractional shares, to exercise voting rights, receive dividends, participate in
distributions and to have the benefit of all other rights of holders of Series
AA Preferred Stock.

                                      A-5
<PAGE>

          IN WITNESS WHEREOF, we have executed and subscribed this Certificate
and do affirm the foregoing as true under the penalties of perjury this 22nd the
day of November, 2000

                              RIBOZYME PHARMACEUTICALS, INC.

                              By:_______________________________________
                                 Name: Ralph E. Christoffersen
                                 Title: Chairman of the Board and
                                        Chief Executive Officer
Attest

By:___________________________
Name: Lawrence Bullock
Title: Vice President and Secretary

                                      A-6
<PAGE>

                                   EXHIBIT B

                          [Form of Right Certificate]

    Certificate No. R-___________                ____ Rights

NOT EXERCISABLE AFTER THE EXPIRATION DATE. AT THE OPTION OF THE CORPORATION, THE
RIGHTS ARE SUBJECT TO REDEMPTION AT $0.01 PER RIGHT OR EXCHANGE FOR COMMON
STOCK, UNDER THE CIRCUMSTANCES AND ON THE TERMS SET FORTH IN THE RIGHTS
AGREEMENT. UNDER CERTAIN CIRCUMSTANCES, RIGHTS BENEFICIALLY OWNED BY AN
ACQUIRING PERSON OR AN ASSOCIATE OR AFFILIATE OF AN ACQUIRING PERSON AND ANY
SUBSEQUENT HOLDER OF SUCH RIGHTS MAY BECOME NULL AND VOID. [THE RIGHTS
REPRESENTED BY THIS RIGHT CERTIFICATE WERE ISSUED TO A PERSON WHO WAS AN
ACQUIRING PERSON OR AN AFFILIATE OR AN ASSOCIATE OF AN ACQUIRING PERSON. THIS
RIGHT CERTIFICATE AND THE RIGHTS REPRESENTED HEREBY ARE VOID IN THE
CIRCUMSTANCES SPECIFIED IN SECTION 7(e) OF THE RIGHTS AGREEMENT.]*

                               Right Certificate

                        RIBOZYME PHARMACEUTICALS, INC.

     This certifies that _______________, or registered assigns, is the
registered owner of the number of Rights set forth above, each of which entitles
the owner thereof, subject to the terms, provisions and conditions of the Rights
Agreement dated as of November 22, 2000 (the "Rights Agreement"), between
Ribozyme Pharmaceuticals, Inc.., a Delaware corporation (the "Company"), and
American Stock Transfer & Trust Company (the "Rights Agent"), to purchase from
the Company at any time after the Distribution Date (as such term is defined in
the Rights Agreement) and prior to 5:00 p.m. Boulder, Colorado, time on the
Expiration Date, as that term is defined in the Rights Agreement, at the
stockholder services office (or such office designated for such purpose) of the
Rights Agent, or its successor as Rights Agent, one one-hundredth of a fully
paid, nonassessable share of the Series AA Junior Participating Preferred Stock,
par value $0.01 per share ("Series AA Preferred Stock"), of the Company, at a
purchase price of $300.00 per one one-hundredth of a share (the "Purchase
Price") upon presentation and surrender of this Right Certificate with the Form
of Election to Purchase duly executed. The number of Rights evidenced by this
Right Certificate (and the number of shares which may be purchased upon exercise
of each Right) and the Purchase Price set forth above, are the number and
Purchase Price as of December 8, 2000 based on the shares of Series AA Preferred
Stock of the Company as constituted at such date.

*    The portion of the legend in brackets shall be inserted only if applicable
and shall replace the preceding sentence.

                                      B-1
<PAGE>

     The Purchase Price and the number of shares of Series AA Preferred Stock
which may be purchased upon the exercise of each of the Rights evidenced by this
Right Certificate are subject to modification and adjustment upon the happening
of certain events as provided in the Rights Agreement.

     This Right Certificate is subject to all of the terms, provisions and
conditions of the Rights Agreement, which terms, provisions and conditions are
hereby incorporated herein by reference and made a part hereof and to which
Rights Agreement reference is hereby made for a full description of the rights,
limitations of rights, obligations, duties and immunities hereunder of the
Rights Agent, the Company and the holders of the Right Certificates. Copies of
the Rights Agreement are on file at the Company and the above-mentioned office
of the Rights Agent and are also available upon written request to the Company.

     This Right Certificate, with or without other Right Certificates, upon
surrender at the stockholder services office (or such office designated for such
purpose) of the Rights Agent, may be exchanged for another Right Certificate or
Right Certificates of like tenor and date evidencing Rights entitling the holder
to purchase a like aggregate number of shares of Series AA Preferred Stock as
the Rights evidenced by the Right Certificate or Right Certificates surrendered
shall have entitled such holder to purchase. If this Right Certificate shall be
exercised in part, the holder shall be entitled to receive, upon surrender
hereof, another Right Certificate or Right Certificates for the number of whole
Rights not exercised.

     Subject to the provisions of the Rights Agreement, the Rights evidenced by
this Certificate may be redeemed by the Company at its option at a redemption
price of $0.005 per Right on or prior to the Stock Acquisition Date (as defined
in the Rights Agreement). In addition, subject to the provisions of the Rights
Agreement, each Right evidenced by this Certificate may be exchanged by the
Company at its option for one share of Common Stock following the Stock
Acquisition Date and prior to the time an Acquiring Person, as that term is
defined in the Rights Agreement, owns 50% or more of the Voting Power, as that
term is defined in the Rights Agreement, of the Company.

     No fractional shares of Series AA Preferred Stock will be issued upon the
exercise of any Rights evidenced hereby (other than fractions which are integral
multiples of one one-hundredth of a share of Series AA Preferred Stock, which
may, at the election of the Company, be evidenced by depositary receipts). In
lieu of fractions of a share, a cash payment will be made, as provided in the
Rights Agreement.

     No holder of this Right Certificate shall be entitled to vote or receive
dividends or be deemed for any purpose the holder of shares of Series AA
Preferred Stock or of any other securities of the Company which may at any time
be issuable on the exercise hereof, nor shall anything contained in the Rights
Agreement or herein be construed to confer upon the holder hereof, as such, any
of the rights of a stockholder of the Company or any right to vote for the
election of directors or upon any matter submitted to stockholders at any
meeting thereof, or to give or withhold consent to any corporate action, or to
receive notice of meetings or other

                                      B-2
<PAGE>

actions affecting stockholders (except as provided in the Rights Agreement), or
to receive dividends or subscription rights, or otherwise, until the Rights
evidenced by this Right Certificate shall have been exercised as provided in the
Rights Agreement.

     This Right Certificate shall not be valid or obligatory for any purpose
until it shall have been countersigned by the Rights Agent.

     WITNESS the facsimile signature of the proper officers of the Company and
its corporate seal

Dated as of __________________.

                                        RIBOZYME PHARMACEUTICALS, INC.

                                        By:____________________________
                                           Its:________________________
                                           Title:______________________

Countersigned:

AMERICAN STOCK TRANSFER & TRUST COMPANY

By:_______________________________

                                      B-3
<PAGE>

                  [Form of Reverse Side of Right Certificate]

                              FORM OF ASSIGNMENT

               (To be executed by the registered holder if such
              holder desires to transfer the Right Certificate.)

     FOR VALUE RECEIVED ____________________________ hereby sells, assigns and
transfers unto _________________________________________________________________
                 (Please print name and address of transferee)
________________________________________________________________________________

this Right Certificate, together with all right, title and interest therein, and
does hereby irrevocably constitute and appoint _____________ Attorney to
transfer the within Right Certificate on the books of the within-named Company,
with full power of substitution.

Dated:__________________      __________________________________________________
                              Signature
                              (Signature must conform in all respects to name of
                              holder as specified on the face of this Right
                              Certificate)

Signature Guaranteed:

     Signatures must be guaranteed by a member or a participant in the
Securities Transfer Agent Medallion Program, the New York Stock Exchange
Medallion Signature Program or the Stock Exchange Medallion Program.

                                  CERTIFICATE

     The undersigned hereby certifies by checking the appropriate boxes that:

     1.   This Right Certificate [_] is [_] is not being sold, assigned and
transferred by or on behalf of a Person who is or was an Acquiring Person or an
Affiliate or Associate of any such Acquiring Person (as such terms are defined
pursuant to the Rights Agreement);

     2.   After due inquiry and to the best knowledge of the undersigned, it [_]
did  [_] did not acquire the Rights evidenced by this Right Certificate from any
Person who is, was or subsequently became an Acquiring Person or an Affiliate or
Associate of an Acquiring Person.

Dated:_________________       __________________________________________________
                              Signature
                              (Signature must conform in all respects to name of
                              holder as specified on the face of this Right
                              Certificate)

                                      B-4
<PAGE>

                         FORM OF ELECTION TO PURCHASE

     (To be executed if holder desires to exercise the Right Certificate.)

To Ribozyme Pharmaceuticals, Inc.:

     The undersigned hereby irrevocably elects to exercise ___________________
Rights represented by this Right Certificate to purchase the shares of Series AA
Preferred Stock issuable upon the exercise of such Rights and requests that
certificates for such shares be issued in the name of:

          Name:__________________________________________

          Address:________________________________________

               _________________________________________

          Social security or taxpayer identification
          number:________________________________________

If such number of Rights shall not be all the Rights evidenced by this Right
Certificate, a new Right Certificate for the balance remaining of such Rights
shall be registered in the name of and delivered to:

          Name:__________________________________________

          Address:________________________________________

               _________________________________________

          Social security or taxpayer identification
          number:________________________________________

Dated:__________________

                              __________________________________________________
                              Signature
                              (Signature must conform in all respects to name of
                              holder as specified on the face of this Right
                              Certificate)

Signature Guaranteed:

                                      B-5
<PAGE>

     Signatures must be guaranteed by a member or a participant in the
Securities Transfer Agent Medallion Program, the New York Stock Exchange
Medallion Signature Program or the Stock Exchange Medallion Program.

                                  CERTIFICATE

     The undersigned hereby certifies by checking the appropriate boxes that:

     1.   The Rights evidenced by this Right Certificate [_] are  [_] are not
being exercised by or on behalf of a Person who is or was an Acquiring Person or
an Affiliate or Associate of any such Acquiring Person (as such terms are
defined pursuant to the Rights Agreement);

     2.   This Rights Certificate [_] is [_] is not being sold, assigned and
transferred by or on behalf of a Person who is or was an Acquiring Person or an
Affiliate or Associate of any such Acquiring Person (as such terms are defined
pursuant to the Rights Agreement);

     3.   After due inquiry and to the best knowledge of the undersigned, it [_]
did [_] did not acquire the Rights evidenced by this Right Certificate from any
Person who is, was or became an Acquiring Person or an Affiliate or Associate of
an Acquiring Person.

Dated:_______________

                              __________________________________________________
                              Signature
                              (Signature must conform in all respects to name of
                              holder as specified on the face of this Right
                              Certificate)

                                    NOTICE

     The signature in the foregoing Forms of Assignment and Election must
conform to the name as written upon the face of this Right Certificate in every
particular, without alteration or enlargement or any change whatsoever.

     In the event the certification set forth above in the form of Assignment or
the form of Election to Purchase, as the case may be, is not completed, the
Company and the Rights Agent will deem the beneficial owner of the Rights
evidenced by this Right Certificate to be an Acquiring Person or an Affiliate or
Associate thereof (as defined in the Rights Agreement) and such Assignment or
Election to Purchase will not be honored as described in Section 7(e) of the
Rights Agreement.

                                      B-6
<PAGE>

                                   EXHIBIT C

                        RIBOZYME PHARMACEUTICALS, INC.

                     SUMMARY OF SERIES AA PREFERRED STOCK
                                PURCHASE RIGHTS

     On November 21, 2000, the Board of Directors of Ribozyme Pharmaceuticals,
Inc. (the "Company") declared a dividend of one preferred share purchase right
(a "Right") for each outstanding share of common stock, par value $.01 per share
(the "Common Stock"). The dividend is payable to the stockholders of record on
December 8, 2000.

     Our Board has adopted this Rights Agreement to protect stockholders from
coercive or otherwise unfair takeover tactics. In general terms, it works by
imposing a significant penalty upon any person or group that acquires 15% or
more of our outstanding common stock without the approval of our Board. The
Rights Agreement should not interfere with any merger or other business
combination approved by our Board.

     For those interested in the specific terms of the Rights Agreement as made
between our Company and American Stock Transfer & Trust Company, as the Rights
Agent, on November 22, 2000, we provide the following summary description.
Please note, however, that this description is only a summary, and is not
complete, and should be read together with the entire Rights Agreement, which
has been filed with the Securities and Exchange Commission as an exhibit to a
Registration Statement on Form 8-A dated November 27, 2000. A copy of the Rights
Agreement is available free of charge from our Company.

THE RIGHTS. Our Board authorized the issuance of a Right with respect to each
share of Common Stock outstanding on December 8, 2000. The Rights will initially
trade with, and will be inseparable from, the Common Stock. New Rights will
accompany any new shares of Common Stock we issue after December 8, 2000 until
the Distribution Date described below.

EXERCISE PRICE. Each Right will allow its holder to purchase from our Company
one one-hundredth of a share of Series AA Junior Participating Preferred Stock
("Preferred Stock") for $300, once the Rights become exercisable. This portion
of a share of Preferred Stock will give the shareholder approximately the same
dividend, voting, and liquidation rights as would one share of Common Stock.
Prior to exercise, the Right does not give its holder any dividend, voting, or
liquidation rights.

EXERCISABILITY. The Rights will not be exercisable until

                                      C-1
<PAGE>

 .    10 days after the public announcement that a person or group has become an
     "Acquiring Person" by obtaining beneficial ownership of 15% or more of our
     outstanding Common Stock, or, if earlier,

 .    10 business days (or a later date determined by our Board before any person
     or group becomes an Acquiring Person) after a person or group begins a
     tender or exchange offer which, if completed, would result in that person
     or group becoming an Acquiring Person.

    We refer to the date when the Rights become exercisable as the "Distribution
Date." Until that date, the Common Stock certificates will also evidence the
Rights, and any transfer of shares of Common Stock will constitute a transfer of
Rights. After that date, the Rights will separate from the Common Stock and be
evidenced by book-entry credits or by Rights certificates that we will mail to
all eligible holders of Common Stock. Any Rights held by an Acquiring Person are
void and may not be exercised.

CONSEQUENCES OF A PERSON OR GROUP BECOMING AN ACQUIRING PERSON.

 .    FLIP IN. If a person or group becomes an Acquiring Person, all holders of
     Rights except the Acquiring Person may, for $300, purchase shares of our
     Common Stock with a market value of $600, based on the market price of the
     Common Stock prior to such acquisition.

 .    FLIP OVER. If our Company is later acquired in a merger or similar
     transaction after the Rights Distribution Date, all holders of Rights
     except the Acquiring Person may, for $300, purchase shares of the acquiring
     corporation with a market value of $600, based on the market price of the
     acquiring corporation's stock, prior to such merger.

PREFERRED STOCK PROVISIONS.

Each whole share of Preferred Stock, if issued:

 .    will not be redeemable.

 .    will entitle holders to quarterly dividend payments of $1 per share, or an
     amount equal to 100 times the dividend paid on one share of Common Stock,
     whichever is greater.

 .    will entitle holders upon liquidation either to receive $100 per share or
     an amount equal to 100 times the payment made on one share of Common Stock,
     whichever is greater.

 .    will have the same voting power as 100 shares of Common Stock and will vote
     as a single class with the Common Stock.

                                      C-2
<PAGE>

 .    if shares of our Common Stock are exchanged via merger, consolidation, or
     a similar transaction, will entitle holders to a per share payment equal to
     the payment made on one hundred shares of Common Stock.

    The value of one one-hundredth interest in a share of Preferred Stock should
approximate the value of one share of Common Stock.

EXPIRATION. The Rights will expire on December 8, 2010.

REDEMPTION. Our Board may redeem the Rights for $.01 per Right at any time
before any person or group becomes an Acquiring Person. If our Board redeems any
Rights, it must redeem all of the Rights. Once the Rights are redeemed, the only
right of the holders of Rights will be to receive the redemption price of $.01
per Right. The redemption price will be adjusted if we have a stock split or
stock dividends of our Common Stock.

EXCHANGE. After a person or group becomes an Acquiring Person, but before an
Acquiring Person owns 50% or more of our outstanding Common Stock, our Board may
extinguish the Rights by exchanging one share of Common Stock or an equivalent
security for each Right, other than Rights held by the Acquiring Person.

ANTI-DILUTION PROVISIONS. Our Board may adjust the purchase price of the
Preferred Stock, the number of shares of Preferred Stock issuable and the number
of outstanding Rights to prevent dilution that may occur from a stock dividend,
a stock split, a reclassification of the Preferred Stock or Common Stock.
Adjustments to the purchase price of less than 1% will be deferred until the
earlier of three years after the transaction requiring the adjustment or the
date the right to exercise the Rights expires.

AMENDMENTS. The terms of the Rights Agreement may be amended by our Board
without the consent of the holders of the Rights. After a person or group
becomes an Acquiring Person, our Board may not amend the Rights Agreement in any
way that adversely affects the holders of the Rights.

                                      C-3<PAGE>

EXHIBIT 10.8

                                                                          [LOGO]
                                                                       INSTITUTO
                                                                        MEXICANO
                                                                 del a Propiedad
                                                                      Industrial

              METODO Y APAETATO PARA LIMITACION DE COMBUSTIBLE

                     EN UN VEHICULO DE CONEUST16N INTERNA

     El senor DWAYNE FOSSEEN, de nacionalidad norteamericana, con domicilio en
206 May Street, P.O. Box 10, ciudad de Radcliffe, Estado de Iowa, Estados Unidos
de Norteamerica, inventor, cede, vende y traspasa a MIDWEST POWER CONCEPTS,
LTD., sociedad norteamericana, con domicilio es 206 MAY Street, P.O. Box 10,
ciudad de Radcliff, Estado de Iowa, Estados Unidos de Norteamerica, que a su
vez, cede, vende Y traspasa a DWAYNE FOSSEEN de nacionalidad norteamericana, con
domicilio en 206 MAY Street, P.O. Box 10, ciudad de Radcliffe, Estado de Iowa,
Estados Unidos de Norteamdrica, todos los derechos invencion que a continuacion
se describe:

                            RESUMEN DE LA INVENCION

     Metodo y aparato para limitar el combustible a un motor de combustion
interna, para reducir amisiones del motor. Se proporcionan montajes que
responden a una o mas condiciones operativas del motor para regular
ajustablemente la posicion abierta maxima de una valvula estranguladora del
motor, para reducir y limitar el gasto de flujo volumetrico maximo de
combustible al motor. Las condiciones operativas incluyen el gasto de flujo de
combustible requerido por el acelerador, la condicion de la transmision de un
vehiculo, la velocidad del mismo y las velocidades y direccion de cualquier
viento

                         ANTECEDENTES DE LA INVENCION

     La invencion se refiere a un aparato para limitacion
<PAGE>

                                       2

                                                                          [LOGO]
                                                                       Institute
                                                                        Mexicano
                                                                del la propicdad
                                                                      Industrial

de combustible, para un vehiculo on motor de combustion ? y mas especificamente
un aparato empleado para modificar un vehiculo de combustion interna, de manera
tal que el gasto maximo de combustible suministrado al motor se restringe de
acuerdo con un plan preseleccionado, dependiente de la velocidad del vehiculo,
el estado de engranaje de la transmision u otras condiciones operativas.

     En la fabricacion de vehiculos de combustion interna, los motores
tipicamente se dimensionan para proporcionar potencia par cumplir con los
requerimientos maximos de la aplicacion particular y restricciones de diseno del
vehiculo. Condiciones operativas del vehiculo, sin embargo varian en un amplio
rango de demandas de potencial, particularmente cuando se hacen consideraciones
por economia de combustible y reduccion de emisiones contaminantes del vehiculo.
Por ejemplo, como bien se conoce, cantidades substanciales de combustible se
desperdician por arrangques con aceleracion completa o integra, en donde el
motor, se sobre alimenta con combustible bajo condiciones transitorias. Recien
se comprende y aprecia que estos arranques con integra aceleracion tambien
resultan en incrementos substanciales de emisiones desde el motor,
particularmente en la forma de hidrocarburos y particulas. En una condicion
sobrealimentado, el motor es incapaz de quemar completamente todo el
combustible, con el resutado de que se emiten hidrocarburos no consumidos. Esta
condiciones tambien reducen
<PAGE>

                                       3

                                                                          [LOGO]
                                                                       INSTITUTO
                                                                        MEXICANO
                                                                 de la Propiedad
                                                                      Industrial

la temperatura de la camara de combustion, lo que lleva a un incremento en la
formacion de emisiones de particulas.

     El uso de la capacidad Integra de la energia del motor, particularmente
para elevada aceleracion a bajas velocidades, produce tensiones excesivas en el
motor, el tren de impulso del vehiculo, la suspension y otros componentes.
Mientras que estos efectos se han reconocido desde hace mucho tiempo y han sido
desalentados tanto por agencias publicas como forma conveniente de forzar el
cumplimiento con las lineas de guia recomendadas.

                           CONPENDIO DE LA INVENCION
                           -------------------------

     La invencion consiste de un aparato para modificar un vehiculo de
combustion interna, de manera tal que la velocidad maxima de combustible
suministrado al motor, se limita a un plan pre-seleccionado que se determina de
acuerdo con la velocidad, la condicion de la transmision vehicular y/o
condiciones de aceleracion del vehiculo. La invencion puede tomar una cantidad
de formas especificas correspondientes al motor de combustion interna particular
y el vehiculo en el cual se practicaran. Por ejemplo, con motores que tienen un
aparato de control electronico sofisticado, la presente invencion consistiria de
una pluralidad de sensores conectados a una unidad de procesamiento central que
se interconecta con y controla el aparato de control electronico del motor de
combustion interna.
<PAGE>

                                       4

                                                                          [LOGO]
                                                                       INSTITUTO
                                                                        MEXICANO
                                                                 de la Propiedad
                                                                      Industrial

Estos sensores detectarian y proporcionarian information a la unidad de
procesamiento central respecto a la velocidad del vehiculo, la condicion de la
transmision del vehiculo, la actitud del vehiculo (ya sea que este ascendiendo o
descendiendo de la pendiente) cualquier condicion de viento frontal y la
posicion del pedal acelerador que se emplea ordinariamente para determinar la
demanda de combustible suministrado al motor. La unidad de procesamiento central
compararia las condiciones percibidas por el detector con el plan seleccionado
de gasto de combustible que previamente se ha almacenado en un aparato de
memoria. Si la velocidad de suministro de combustible demandado por el
acelerador excede la del plan o programa, la unidad de procesamiento central
enviara una senal al aparato de control electronico combustible del suministrado
al motor en la cantidad planeada preseleccionada.

          En una modalidad alternativa aplicable a combustiones internas que
tienen montajes mecanicos para controlar la velocidad de combustible
suministrado al motor, la unidad de procesamiento central controla un motor
escalonador que mueve un tope ajustable para el aparato de suministro de gasto
de combustible al motor de nuevo para restringir el gasto maximo de combustible
a aquel del plan preseleccionado.

          En una modalidad tercera, menos sofisticada, una pluralidad de
accionadores lineales se emplean para ajustar un
<PAGE>

                                       5

                                                                          [LOGO]
                                                                       INSTITUTO
                                                                        MEXICANO
                                                                 de la Propiedad
                                                                      Industrial

tope para el aparato para control de gasto de combustible del motor.  Los
accionadores son ajustados para mover el tope a una posicion preseleccionada por
cado uno de los engranajes de la transmision del vehiculo. De acuerdo con esto,
la velocidad maxima de flujo de combustible que se suministrara al motor, cuando
el vehiculo esta en la primer o mas baja velocidad de la transmision, se ajusta
por un primer accionador lineal. Una cantidad maxima segunda, algo superior de
gasto de combustible se ajusta a una cantidad preseleccionada de movimiento por
el tope, mediante un segundo accionador lineal y asi en adelante para cada una
de las velocidades superiores.

          Con respecto a cada una de las modalidades, la potencia perdida debido
a limitar el combustible primario del motor, puede compensarse parcialmente por
la adicion de un combustible de alcohol hidratado en el multiple de alimentacion
del motor.

          De acuerdo con esto, un objeto de la presente invencion consiste en
proporcionar un aparato para modificar un vehiculo con motor de
combustion interna, para restringir el gasto de flujo maximo de combustible al
motor, de acuerdo con un plan preseleccionado que depende de la velocidad del
vehiculo.

          Otro objetivo de la invencion consiste en proporcionar este aparato,
en donde el plan es substancialmente continuo con los cambios en velocidad del
vehiculo.

          Un objetivo adicional de la invencion consists en
<PAGE>

                                       6

                                                                          [LOGO]
                                                                       Instituto
                                                                        Mexicano
                                                                 de la Propiedad
                                                                      Industrial

proporcionar este aparato, en donde el plan cambia el gasto de flujo maximo de
combustible al motor, en etapas discretas que incrementan conforme aumenta la
velocidad del vehiculo.

     Aun otro objeto de la invencion consiste en proporcionar este aparato, en
donde el gasto maximo de combustible al motor se restringe a un valor
preseleccionado por cada velocidad que se emplea por el vehiculo.

     Aun otro objeto de la invencion consiste en proporcionar un aparato para
restriccion de gasto de combustible, que permite limitaciones en la potencia
disponsible de un motor que esta preseleccionado y fuera del control del control
del operador del vehiculo.

     Aun otro objeto adicional de la invencion consiste en proporcionar un
aparato para restringir el gasto maximo de combustible a un motor de combustion
interna, que resulta en eficiencia de combustible incrementada y emisiones
reducidas.

     Un objetivo aun adicional de la invencion consiste en proporcionar un
aparato para restringir el gasto maximo de combustible a un motor de combustion
interna, en donde la fumigacion de combustible de alcohol hidratado en el
multiple de alimentacion del motor, cuando menos restaura parcialmente el
decremento en potencia del motor:

     Estos y otros objetivos de la invencion seran aparentes a partir de la
siguiente descripcion de las modalidades preferidas.
<PAGE>

                                       7

                                                                          [LOGO]
                                                                       Instituto
                                                                        Mexicano
                                                                 de la Propiedad
                                                                      Industrial

                       BREVE DESCRIPCION DE LOS DIBUJOS
                       --------------------------------

          La Figura 1 es una vista en planta parcial de un motor de combustion
interna que se ha modificado por el aparato de la presente invencion.

          La Figura 2 es una vista en detalle agrandada del aparato de
restriccion para el gasto de combustible de figura 1.

          La Figura 3 es una vista lateral que corresponde a la Figura 2, con
parte de la caja de control regulador despiezada para mostrar partes interiores
del control regulator.

          La Figura 4 - 6 son vistas en planta en escala reducidas del aparato
ilustrado en tres diferentes condiciones que corresponden a los ajustes de las
tres velocidades de la transmision del vehiculo;

          La Figura 7 es una vista en planta DE la caja de control reguladora
con partes desplazadas para mostrar partes interiores del control regulador;

          La Figura 8 es una vista en planta de otra modalidad alternativa en
donde el gast de combustible maximo del aparato de control de gasto de
combustible mecanio del motor se a justa por un motor escalonador;

          La Figura 9 es una representacion grafica de aceleracion de vehiculo
contra tiempo para un vehiculo no modificado y como se modifica por una
modalidad de la presente invencion.

          La Figura 10 es una representacion grafica de la
<PAGE>

                                       8

                                                                          [LOGO]
                                                                       Instituto
                                                                        Mexicano
                                                                 de la Propiedad
                                                                      Industrial

velocidad del vehiculo contra tiempo para un vehiculo modificado y modificado
por una modalidad de la presente invencion;

          La Figura 11 es una representacion grafica de opacidad de humo contra
tiempo para un vehiculo no modificado y modificado por una y modalidad de la
presente invencion; y

          Las Figuras 12a y 12b son representaciones graficas de opacidad de
humo contra tiempo para un vehiculo modificado y modificado por una modalidad de
la presente invencion, en donde los vehiculos se guian sobre rutas identicas.

               DESCRIPCION DETALLADA DE UNA MODALIDAD PREFERIDA
               ------------------------------------------------

          Ilustrado en la Figura 1, generalmente en 10, se encuentra un aparato
licitador de gasto de combustible de la presente invencion ilustrado conectado a
un motor de combustion interna 12 de un vehiculo. Un aparato regulador 14 se
monta sobre una caja de control reguladora 16. Un par de varillas conectantes
18a y 18b se extienden en direcciones opuestas desde cualquier lado de la caja
de control reguladora 16, en donde se conectan pivotalmente en la porcion de
extremo exterior de la misina, a uno de un par de rejillas de ajuste inyector de
combustible 20a y 20b. El movimiento axial de las varillas conectantes 18 de
esta -manera ajustara el gasto de combustible que circule a traves de una
pluralidad de inyectores de combustible 22a-h, para su-ministro del motor de
combustion interna 12.
<PAGE>

                                       9

                                                                          [LOGO]
                                                                       Instituto
                                                                        Mexicano
                                                                 de la Propiedad
                                                                      Industrial

          El vehiculo incluye un acelerador operado por pedal (no mostrado) del
tipo usual. En vez de estar conectado por una articulacion mecanica al aparato
regulador 14, el acelerador opera  una unidad de envio de aire a presion que
se conecta al aparato regulador 14 por una linea de aire 24. La presion de la
linea o tuberia de aire 24 (de cero a 4.22 kg/CM/2/ (de 0 a 60 psi)) provoca que
un piston 26 de la unidad de valvula 28 se extienda o retraiga en respuesta a
cambios en posicion del acelerador de pie. La extension y retraccion del piston
26 pivotea una palanca de control de velocidad 30 respecto a su montaje pivotal
32 sobre la caja de control reguladora 16.

          La caja de control reguladora 16 incluye una placa superior 34 en la
cual se monta la unidad de valvula 28 y la
palaca para control de velocidad 30. Tambien se monta en la placa superior 34
una palanca de tope 36, de la cual la funcion se describira a continuacion. La
palanca de tope 36 se monta para movimiento pivotal en una flecha vertical que
se extiende a traves de la placa superior 34. Un resorte de retorno 38 recibe
aproximadamente la flecha vertical de la palanca de tope 36 por debajo de la
placa superior 34, guia la palanca de tope a su posicion loca, inactiva o
desconectada. El montaje pivotal 32 de la palanca para control de velocidad 30
tambien se extiende a traves de la placa superior 34 y tiene conectado a su
porcion de extremo de fondo, un brazo de palanca horizontalmente extendido 40,
la procion de extremo libre del cual se movera en
<PAGE>

                                      10

                                                                          [LOGO]
                                                                       Instituto
                                                                        Mexicano
                                                                 de la Propiedad
                                                                      Industrial

un arco por movimiento pivotal del montaje de pivote palanca para control de
velocidad 30.

     Una f lecha operadora principal 42 se monta para movimiento pivotal
respecto a un eje vertical dentro de la caja de control regulador 16. Conectada
a la porcion de extremo superior de la flecha operadora 42 se encuentra una
palanca de flecha operadora 44, que tiene un par de brazos de palanca, un brazo
de tope 46 y brazo regulador 48. Una palanca diferencial 50 se monta
pivotalmente en la porcion de extremo libre del brazo regulador 48. La palanca
diferencial 50 incluye un brazo de palanca reguladora 52, que tiene una porcion
de extremo ranurada o en forma de U, dentro de la cual se recibe una pieza
conectante 54 que horizontalmente 40. depende del brazo de palanca extendido La
palanca diferencial 50 tambien incluye un brazo de barra conectarte 56, que
pivoteara junto con el brazo de articulacion regulador 52, por movimiento de la
palanca para control de velocidad 30 como se describio anteriormente. Una barra
conectora 59 se conecta a la porcion de extremo libre del brazo de palanca
conectado en 56, por un montaje pivotal 58, de manera tal que el movimiento
pivotal de la palanca dif erencial 50 provoque movimiento axial de la barra de
conector en 59

     Un brazo regulador 61 se monta para movimiento pivotal respecto a un eje
fijo en 63. Una porcion de extremo 65 de brazo regulador 61 se conecta
pivotalmente al extremo de la
<PAGE>

                                      11

                                                                          [LOGO]
                                                                       Instituto
                                                                        Mexicano
                                                                 de la Propiedad
                                                                      Industrial

barra conectante 59 opuesto al brazo de palanca coneet P 5 6. enci.,In 1 De
acuerdo con esto, la depresion del pedal acelerador resultara en un movimiento
pivotal manecillas del reloj del en sentido contrario brazo regulador 61. al La
de varilla conectante 18b se conecta a la porcion de extremo 65 del brazo
regulador 61 Y la otra varilla conectante 18a se conecta a la otra porcion de
extremo 67 del brazo regulador 61, con el resultado del brazo regulador 61
ajusta el gasto volumetrico de combustible que circula extiende hacia arriba a
al motor. traves de La varilla pivote la PLACA superior 34 63 se y se sujeta a y
monta para movimiento pivotal a la palanca de tope 36. SI la palanca de tope 36
se restringe contra movimiento, el brazo regulador 61 tambien se restringira, de
manera tal ningun ajuste mayor del gasto de volumen de combustible pueda
hacerse.

     Incluido en la caja de control de regulador encuentra un montaje de peso
regulador 60 montado en una flecha de peso horizontal 62, que se gira
corresponde a la velocidad del motor. a una velocidad EL regulador actua en
asociacion con la flecha operadora y un brazo de tope 46 para proporcionar un
limite en el grado de movimiento del brazo de barra conectante 56 en la forma
usual por acoplamiento del brazo de barra conectante 56 con un tornillo de
ajuste 64 montado en la porcion de extremo libre del brazo de tope 46

     La placa superior 34 de la caja de control reguladora
<PAGE>
                                      12

                                                                          [LOGO]
                                                                       Instituto
                                                                        Mexicano
                                                                 de la Propiedad
                                                                      Industrial

16 soporta ordinariamente un ajustable POSICION abierta maxima para la palanca
de tope 36 Y de acuerdo con esto el gasto de f lujo maximo de combustible al
motor 12. De acuerdo CON la proporciona, que presente invencion, es ajustable en
un tope respuesta ajustable se preseleccionado, combustible del para motor
parametros deseados. regular el gasto de f lujo 12, en cumplimiento con a un
maxiiiio uno 0 El aparato para proporcionar un plan inas tope ajustable incluye
un accionador central 64 y una unidad loca o inactiva remota 66. El accionador
central 64 se monta cualquier posicion conveniente para la conexion de la
tuberia o 1 inea de aire 24 desde el pedal acelerador y la unidad secundaria o
inactiva remota 66 se coloca en la placa superior 34 de la caja de control
reguladora 16, generalmente en el area en la cual se ubica el tope fijo.

El accionador central 64 como se i lustra Figuras 1- 3 , consiste de una placa
base 68 en la en CUAL se monta un bloque 70, un cilindro extensible y retraible
accionado por aire 72, y primer y segundo cilindros de aire controlados
electricamente 74 y 76, respectivamente. Un cable 78 interconecta la unidad loca
o inerte remota 66 y el cilindro de aire 72, DE manera tal QUE la extension Y
retraccion DE una PORCION de cable intercoaxial piston 82 de la unidad loca 80
por el remota 66. La porcion coaxial
<PAGE>

                                      13

                                                                          [LOGO]
                                                                       Instituto
                                                                        Mexicano
                                                                 de la Propiedad
                                                                      Industrial

exterior del cable 78 se fija.a un bloque 70 y al alojamiento exterior de la
unidad loca remota 66.

          Montado en el bloque 70 Y extendido en la linea de accion del cilindro
de aire 72 se encuentran un par de topes roscados, primeros topes 84 y secjundos
topes 86. Las posiciones de las porciones de extremo del primer y segundo topes
84 y 86 son ajustables a una posicion fija deseada por una tuerca de sujecion
correspondiente 88a u 88b. Como se ilustra en la Figura 2, el primer tope 84 se
extiende desde el bloque 80 algo mas cerca al cilindro de aire 72 que el segundo
tope 86.

          El primer y segundo cilindros de aire controlados electricamente 74 y
76 se montan pivotalmente 90 y 92, respectivamente en la placa base 80 en
cualquier lado del cilindro de aire 72. El extremo libre de un piston extensible
retraible 94 del primer cilindro de aire conectado electricamente 74, se conecta
pivotalinente a un primer bloque pivote 96 montado para movimiento pivotal en 98
en la placa base 68. Un rodillo 100 se monta para movimiento rotacional en el
primer bloque pivote 96. en una forma similar la porcion de extremo libre de un
piston 102 del segundo cilindro de aire controlado electricamente 76, se monta
pivotalmente a un segundo bloque de pivote 104 que se monta pivotalmente en 106
a la placa base 68. El segundo bloque de pivote 104 tambien soporta para
movimiento rotacional de un segundo rodillo 108.

          Cada uno de los cilindros de aire 72-76 se conectan a
<PAGE>

                                      14

                                                                          [LOGO]
                                                                       Instituto
                                                                        Mexicano
                                                                 de la Propicdad

la linea o tuberia de aire 24. Los cilindros de aire 14 y 76 tambien se conectan
mediante los cables electricos 110 y 112, respectivamente a un transpondedor
conectado a la transmision de tres velocidades (no mostrada del vehiculo. De
acuerdo con esto, el cilindro de aire 72 se extiende y retrae en respuesta a la
posicion de pedal acelerador, de manera tal que ante extension completa, como se
ilustra en la Figura 4, en donde una placa 114 se conecta a la porcion de
extremo libre del piston, confina al bloque 70, corresponde a la posicion minima
o inerte del pedal acelerador. En esta posicion, el cable intercoaxial 80 esta
en su posicion maxima extendida desde la unidad remota 66. lineal Conforme se
oprime el pedal acelerador, el accionador 72 retraera el piston y placa 114
hasta que entre en contacto con cualquiera de los rodillos 100 o 108. Si la
transmission esta en primer velocidad, correspondiente si a la la Figura 5, el
primer cilindro a la Figure 5, el primer cilidro de aire electricamente
controlado 74 se extendera hasta que el rodillo 100 entre en contacto con primer
tope 84, el contacto de la placa 114 con el primer rodillo 100, detendra la
retraccion del cilindro de aire 72, ya sea que el pedal de acelerador se halla
oprimido o no mas alla de la ubicacion correspondiente. Esto resultara en
retraccion del cable intercoaxial 80, para permitir movimiento contrario de las
manecillas del reloj adicional de la palanca de tope 36.

     En vez de esta, si la transmision del vehiculo esta en segunda velocidad,
el primer cilindro de aire electricamente
<PAGE>

                                      15

                                                                          [LOGO]
                                                                       Instituto
                                                                        Mexicano
                                                                 de la Propiedad
                                                                      Industrial

controlado 74 se retraera y el segundo cilindra de aire electricamente
controlado 76 se extendera hasta que el rodillo 108 entre en contacto con el
segundo tope 86, como se ilustra en la Figura 6. En esta condicion, la depresion
del pedal acelerador retraera el cilindro de aire 72, hasta que la placa 114
entra en contacto con el rodillo 108. Como con anterioridad, la extension del
cable intercoaxial 80 mas alla de la unidad loca o inerte remota 66, se ajustara
para proporcionar una posicion de tope para la palanca de tope 36.

     Finalmente, si la transmision del vehiculo esta en tercer velocidad, ambos
cilindros de aire electricamente controlados 74 Y 73 se retraeran completamente,
como se ilustra en la Figura 4, de manera tal que la depresion integra del pedal
acelerador permitira la retraccion del cilindro de aire 72 hasta que la placa
114 entra en contacto con los rodillos 100 y 108. El accionador central se ha
construido y ajustado de manera tal que esta posicion permite el gasto completo
de suministro de combustible al motor como se permite por el motor no
modificado.

     La presente invencion se emplea ventajosamente en un motor de combusition
interna modificado como se describe en la patente de los E.U.A. 4,958,598 que se
incorpora aqui por esta referencia. La patente '598 muestra el uso de un
combustible de alcohol hidratado de baja graduacion, empleado para suplementar
el combustible primario del motor. Las Figuras 9 a 12 representan datos
graficamente tomados a partir de un autobus de
<PAGE>

                                       16

                                                                          [LOGO]
                                                                       Instituto
                                                                        Mexicano
                                                                 de la Propiedad
                                                                      Industrial

9 metros (30 pies) General Motors RTS que tiene un motor no turbocargado 8V71
Detroit Diesel, modificado con el aparato de la presente invencion, como se
describe en las Figuras 1 a 6 de esta solicitud y un aparato de la patente '598.
El camion modificado se probo para aceleracion y opacidad de humo sobre
condiciones de ruta urbana tipicas y estos datos en comparacion con datos que se
toman del camion no modificado bajo condiciones identicas.

     Como una modalidad alternativa, un motor escalonador 120 se monta en la
placa superior 34 de la caja de control reguladora 16 (Fig. 8). El motor
escalonador 120 tiene un tornillo 122 que es extensible y retraible en
incrementos fino, exacto y reproducible. El extremo 124 del tornillo 122 sirve
como un tope para la palanca de tope 36 en la misma forma que el extremo del
cable 80 (Figs. 2, 4-6) en la primer modalidad. El motor escalondor 120 se
controla electricamente y puede operarse convenientemente por un microprocesador
que se conecta a una pluralidad de transductores, para detectar diversas
condiciones de operacion, tales como velocidad del viento. Un potenciometro
ajustado por un pedal acelerador tambien se conecta al microprocesador. El motor
escalonador 120 es capaz de ajustar la posicion de la palanca de tope 36 en
aproximadamente 500 divisiones substancialmente equiespaciadas, para permitir un
mucho mayor grado de flexibilidad en el limite
<PAGE>

                                      17

                                                                          [LOGO]
                                                                       Instituto
                                                                        Mexicano
                                                                 de la propiedad
                                                                      Industrial

del gasto de flujo de combustible maximo al motor ? pluralidad de condiciones
operativas.

     En Figura 9, la aceleracion de los dos vehiculos con el tiempo se
representa, mostrando que se experimenta algun decremento en aceleracion. Este
decremento, sin embargo no es tan notable como para ser materia de comentarios
negativos por los conductores de los vehiculos.

     La velocidad de los dos vehiculos con el tiempo se ilustra en la Figura 10.
De nuevo, se observo algo de reduccion en desempeno, es decir una reduccion en
la velocidad promedio(en una distancia de 442.6 metros (1452 pies con un grado
promedio de 1.55 pro ciento)) desde 42.64 a 37.8 km por hora (26.5 m.p.h. a 23.5
m.p.h.). Sin embargo, se logro un ahorro primario en combustible de 17.2 por
ciento.

     La opacidad de los escapes emitidos por los dos vehiculos se midio sobre la
secuencia de aceleracion de la Figura 9, empleando un opacimetro Celisco
modelo 200, como se ilustra en la Figura 11. El vehiculo modificado tuvo una
opacidad substancialmente reducida de la emision particularmente durante las
etapas tempranas de la secuencia de aceleracion. Las mediciones de opacidad de
humo sobre una ruta urbana tipica del vehiculo no modificado (Figura 12a) y el
vehiculo modificado (Fig. 12b), se midieron. La reduccion en opacidad de
emision se marca.

                              NOVEDAD DEL INVENTO
                              -------------------
<PAGE>

                                      18

                                                                          [LOGO]
                                                                       Institute
                                                                        Mexicano
                                                                 de la Propiedad
                                                                      Industrial

     Habiendose descrito la invencion como antecede, se reclama como propiedad
lo contenido en las siguientes

REIVINDICACIONES

     1.  Aparato limitador de combustible para un motor de combustion interna,
conectado operativamente a una transmision capaz de ser operada en una velocidad
controlada con un primer engranaje y un segundo engranaje, medio estrangulador
u obturador de combustible a traves del cual se suministra el combustible al
motor controlado por un acelerador, cuyo aparato limitador de combustible se
caracteriza porque comprende:

     (a) madios para limitar a un primer valor el gasto o la tasa maxima de
flujo de combustible a traves del medio de estrangulador, solicitado por medio
del acelerador para asi reducir la salida o rendimiento maximo de potencia del
motor a un primer rendimiento de potencia, en donde dicho primer rendimiento de
potencia, en donde dicho primer rendimiento de potencia es menor que un
rendimiento de potencia sin restricciones del motor que resulta de un flujo de
combustible sin restricciones a traves del medio estrangulador;

     (b) medios para incrementar a un segundo valor la tasa maxima de flujo de
combustible a traves del medio estrangulador, solicitado por medio del
acelerador para asi incrementar la salida o rendimiento de potencia, siendo
dicho segundo rendimiento de potencia mayor que el primer rendimiento
<PAGE>

                                      19

                                                                          [LOGO]
                                                                       Instituto
                                                                        Mexicano
                                                                 de la Propiedad

     de potencia;

          (c) en donde los medios que limitan al primer valor reducen el
     rendimiento del motor a dicho primer rendimiento de potencia cuando la
     transmision se esta operando en el primer engranaje; y

          (d) en donde los medios que incrementan al segundo valor aumentan el
     rendimiento maximo de potencia del motor a dicho segundo rendimiento de
     potencia cuando la transmision se esta operando en el segundo engranaje.

          2. Aparato limitador de combustible para combustion interna instalado
     en un vehiculo, motor un medio estrangulador u obturador de combustible a
     traves del cual se suministra combustible al motor, controlado por un
     acelerador, cuyo aparato limitadorn de combustible se un motor de
     incluyendo el

          (a) medios para limitar a un de valor seleccionado de una pluralidad
     de valores fijos de tasa maxima de flujo de combustible a traves del medio
     estrangulador, solicitada por medio del acelerador para asi reducir la
     salida o rendimiento maximo de potencia del motor

          (b) medios para percibir o detectar la inclinacion del vehiculo; y

          (c) en donde dicha tasa maxima de flujo de combustible es ajustada en
     respuesta a la aceleracion del vehiculo de acuerdo a un inventario o plan
     preseleccionado
<PAGE>

                                      20

                                                                          [LOGO]
                                                                       Instituto
                                                                        Mexicano
                                                                 de la Propiedad
                                                                      industrial

     3. Aparato limitador de combustible como se define en la
reivindicacion 1, caracterizado en que el motor se instala en
un vehiculo y ademas porque comprende medios para percibir o
detectar la aceleracion del vehiculo y en donde dicho valor
fijo seleccionado de la tasa maxima de flujo de combustible se
ajusta en respuesta a la aceleracion del vehiculo de acuerdo a
un inventario o plan preseleccionado.

     4. Aparato limitador de combustible como se define en la
reivindicacion 1, caracterizado en que dicho valor fijo
seleccionado de la tasa maxima de flujo de combustible resulta
en una disminucion de emisiones desde EL motor

     5. Aparato limitador DE combustible como se define en la
reivindicacion 1, caracterizado en que dicho segundo rendimiento
de potencia es igual a dicho rendimiento de potencia sin restricciones
del motor 1que resulta del flujo de combustible sin restricciones a
traves del medio estrangulador.

     EN TESTIMONIO DE LO CUAL, he firmado la anterior descripcion, como
apoderado de DWAYNE FOSSEEN, en la ciudad de Mexico, Distrito Federal, hoy dia
21 de Abril de 1992.

     P.P.                                         DWAYNE FOSSEEN

                                        -------------------------------------
                                        JAIME DELGADO R. y/o SAMUEL DORANTES F.
Jcslegz*
~
<PAGE>

                                                                          [LOGO]
                                                                       Instituto
                                                                        Mexicano
                                                                 de la Propicdad
                                                                      Industrial

[FIG. 1 APPEARS HERE]

<PAGE>

                                                                          [LOGO]
                                                                       Instituto
                                                                        Mexicano
                                                                 de la Propicdad
                                                                      Industrial

[FIG. 2 APPEARS HERE]

<PAGE>

                                                                          [LOGO]
                                                                       Instituto
                                                                        Mexicano
                                                                 de la Propicdad
                                                                      Industrial

[FIG. 3 APPEARS HERE]

<PAGE>

                                                                          [LOGO]
                                                                       Instituto
                                                                        Mexicano
                                                                 de la Propicdad
                                                                      Industrial

[FIG. 4 APPEARS HERE]

[FIG. 5 APPEARS HERE]

[FIG. 6 APPEARS HERE]

<PAGE>

                                                                          [LOGO]
                                                                       Instituto
                                                                        Mexicano
                                                                 de la Propicdad
                                                                      Industrial

[FIG. 8 APPEARS HERE]

[FIG. 7 APPEARS HERE]

<PAGE>

                                                                          [LOGO]
                                                                       Instituto
                                                                        Mexicano
                                                                 de la Propicdad
                                                                      Industrial

[FIG. 9 APPEARS HERE]

<PAGE>

                                                                          [LOGO]
                                                                       Instituto
                                                                        Mexicano
                                                                 de la Propicdad
                                                                      Industrial

[FIG. 10 APPEARS HERE]

[FIG. 11 APPEARS HERE]

<PAGE>

                                                                          [LOGO]
                                                                       Instituto
                                                                        Mexicano
                                                                 de la Propicdad
                                                                      Industrial

[FIG. 12A APPEARS HERE]

[FIG. 12b APPEARS HERE]

Source: [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00018-of-00352.parquet"}, [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00018-of-00352.parquet"}]]