EXHIBIT 3.6

              CERTIFICATE OF DESIGNATIONS, PREFERENCES AND RIGHTS
                                      OF
                           SERIES E PREFERRED STOCK
                                      OF
                                 MAXYGEN, INC.

          Maxygen, Inc., a Delaware corporation (the "Corporation"), organized
and existing under the laws of the State of Delaware, the Certificate of
Incorporation of which was filed in the office of the Secretary of State of
Delaware on May 7, 1996, does by its President and under its corporate seal
hereby certify as follows:

          FIRST:  That by the Certificate of Incorporation duly filed in the
above state, the total number of shares which this corporation may issue is
stated by paragraph FOURTH to be as follows:

     "The total number of shares of all classes of capital stock which the
     corporation shall have authority to issue is Seventy-five Million
     (75,000,000) shares, comprised of Fifty Million (50,000,000) shares of
     Common Stock with a par value of $0.0001 per share (the "Common Stock") and
     Twenty-five Million (25,000,000) shares of Preferred Stock with a par value
     of $0.0001 per share (the "Preferred Stock")";

and, by said Certificate of Incorporation, the shares of the Preferred Stock are
authorized to be issued in one or more series as may be determined from time to
time by the board of directors, each of such series to be distinctly designated.

          SECOND:  That pursuant to the authority so vested, in the board of
directors by the Certificate of Incorporation, the board of directors by
unanimous written consent adopted the following resolutions:

          RESOLVED, that a series of the class of Preferred Stock of the
Corporation be hereby created, and that the designation and amount thereof and
the voting powers, preferences and relative, participating, optional and other
special rights of the shares of such series, and the qualifications, limitations
or restrictions are as follows:

     A.   SERIES E PREFERRED STOCK
          ------------------------

          1.  Designation of Series.
              ---------------------

          800,000 shares of the Preferred Stock of the Corporation shall
constitute a series of Preferred Stock designated as Series E Preferred Stock
("Series E Preferred"), the powers, preferences and relative and other rights
and the qualifications, limitations and restrictions of which are fixed and
determined in this Section A.


          2.   Dividends.
               ---------

          The holders of the then outstanding shares of Series E Preferred shall
be entitled to receive, when, as and if declared by the Board out of any funds
legally available therefor, noncumulative dividends at the rate of $0.50 per
share (as adjusted for any stock dividend, combination or split with respect to
such shares) per annum.  No dividends shall be paid on any other series of
Preferred Stock of the Company unless dividends are paid ratably, in proportion
to the respective annual dividend rates fixed therefor, on the Series E
Preferred.  No dividends (other than those payable solely in Common Stock) shall
be paid or declared on the Common Stock during any fiscal year of the
Corporation until dividends in the total amount of $0.50 per share (as adjusted
for any stock dividend, combination or split with respect to such shares) on the
Series E Preferred shall have been paid or declared and set apart during such
fiscal year.  So long as shares of Series E Preferred remain outstanding, no
dividends shall be paid or declared on the Common Stock at an annual rate in
excess of $0.50 per share (as adjusted for any stock dividend, combination or
split with respect to such shares) or on any other shares of Preferred Stock at
a rate per share of more than 8% of the liquidation preference of such shares of
Preferred Stock.  No right shall accrue to holders of shares of Series E
Preferred by reason of the fact that dividends on such shares are not declared,
nor shall any undeclared or unpaid dividends bear or accrue interest.

          3.   Liquidation Rights.
               ------------------

               (a)  In the event of any (i) reorganization, merger or
consolidation of the Corporation in which the holders of the Common Stock and
Preferred Stock of the Corporation immediately preceding the reorganization,
merger or consolidation do not own 50% or more of the capital stock of the
entity surviving such reorganization, merger or consolidation, or if such
capital stock is not entitled to elect a majority of the directors of the
surviving entity, (ii) sale, lease, assignment, license, transfer or other
conveyance of all or substantially all the assets of the Corporation or (iii)
liquidation, dissolution or winding up of the affairs of the Corporation,
whether voluntary or involuntary, (collectively, a "Liquidating Event"), after
payment or provision for payment of the debts and other liabilities and
obligations of the Corporation and subject to Section A(3)(c) below, the holders
of each share of Series E Preferred then outstanding shall be entitled to elect
to be paid out of the net assets of the Corporation available for distribution
to its stockholders, before any payment or declaration and setting apart for
payment of any amount shall be made in respect of the Common Stock, an amount
equal to $6.25 per share of Series E Preferred (as adjusted for any stock
dividend, combination or split with respect to such shares), plus an amount
equal to any previously declared but unpaid dividends thereon (collectively, the
"Series E Liquidation Preference"). In the event insufficient funds are
available to pay the Series E Liquidation Preference together with any
liquidation preference payable on any other series of Preferred Stock of the
Company, the net assets of the Company shall be paid ratably to the holders of
Series E Preferred and any other series of Preferred Stock that have such rights
in proportion to the preferential amount each such holder is otherwise entitled
to receive.

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               (b)  After payment in full of the Series E Liquidation Preference
and the liquidation preference payable on any other series of Preferred Stock,
the remaining net assets of the Corporation available for distribution shall be
distributed ratably to the holders of Common Stock in proportion to the number
of shares of Common Stock held by them.

               (c)  Upon the occurrence of a Liquidating Event described in
clauses (i) or (ii) of Section A(3)(a) above, the holders of a majority of the
shares of Series E Preferred then outstanding shall have the right to elect on
behalf of all of the holders of Series E Preferred the benefits of the
provisions of Section A(5)(i) below in lieu of receiving payment of the Series E
Liquidation Preference and other payments pursuant to this Section A(3).

          4.   Voting Rights.
               -------------

          Except as otherwise expressly provided herein or as required by law,
the holders of each share of Series E Preferred shall be entitled to vote on all
matters upon which holders of Common Stock have the right to vote and with
respect to such vote, shall be entitled to notice of any stockholders' meeting
in accordance with the Bylaws of the Corporation, and shall be entitled to a
number of votes equal to the largest number of full shares of Common Stock into
which such shares of Series E Preferred could be converted, pursuant to the
provisions of Section A(5) below, at the record date for the determination of
stockholders entitled to vote on such matters or, if no such record date is
established, at the date such vote is taken or any written consent of
stockholders is solicited.  Except as otherwise expressly provided herein or to
the extent class or series voting is otherwise required by law or agreement, the
holders of shares of Series E Preferred, the holders of any other series of
Preferred Stock that have such voting rights and the holders of Common Stock
shall vote together as a single class and not as separate classes on all
matters.

          5.   Conversion.
               ----------

          The holders of the Series E Preferred shall have the following
conversion rights (the "Conversion Rights"):

               (a)  Right to Convert. Each share of Series E Preferred shall be
                    ----------------
convertible, at the option of the holder thereof, at any time after the date of
issuance of such share but prior to the closing date for a Qualified Public
Offering (as that term is hereinafter defined), at the office of the Corporation
or any transfer agent, into fully paid and nonassessable shares of Common Stock,
at the Conversion Price (as that term is hereinafter defined) therefor in effect
at the time of conversion determined as provided in this Section A(5) without
payment of any kind. A "Qualified Public Offering" shall mean an underwritten
public offering of the Corporation's Common Stock registered under the
Securities Act of 1933, as amended, the gross proceeds of which to the
Corporation and/or selling stockholders, if any, are at least $10 million
(before deducting any underwriting fees or selling commissions), provided that
the public offering price per share (before deducting any underwriting fees or
selling commissions) is at least $8.00 per share (as adjusted for any stock
dividend, combination or split with respect to such shares).

                                       3


               (b)  Conversion Price. Shares of Series E Preferred shall be
                    ----------------
convertible into the number of shares of Common Stock that results from dividing
$6.25 by the Conversion Price per share in effect at the time of conversion for
each share of Series E Preferred being converted. The Conversion Price per share
for the Series E Preferred at the date on which the first share of the Series E
Preferred is issued (the "Original Issue Date") shall be $6.25 and shall be
subject to adjustment from time to time thereafter as provided in this Section
A(5).

               (c)  Automatic Conversion. Each share of Series E Preferred which
                    --------------------
remains outstanding on the closing date for a Qualified Public Offering (the
"Registration Date") shall automatically, and without any action on the part of
the holder thereof or the Corporation, be converted on the same basis and at the
same Conversion Price as if each holder thereof had properly exercised his right
to convert on the day next preceding the Registration Date; provided that (i)
such conversion shall be effective immediately prior to the consummation of a
Qualified Public Offering and (ii) the Corporation shall have no obligation to
issue and deliver to any such holder of Series E Preferred on such date a
certificate for the number of shares of Common Stock to which he shall be
entitled until such time as such holder shall have surrendered his certificate
or certificates for his Series E Preferred, duly endorsed, at the office of the
Corporation or any transfer agent or the holder notifies the Corporation that
such certificate or certificates have been lost, stolen or destroyed and
executes an agreement satisfactory to the Corporation to indemnify the
Corporation from any loss incurred by it in connection therewith. All rights
with respect to shares of Series E Preferred outstanding on the Registration
Date shall forthwith after the Registration Date terminate, except only the
right of the holders of such shares to receive Common Stock upon surrender of
their certificates for the Series E Preferred.

               (d)  Mechanics of Conversion; Unpaid Dividends. Before any holder
                    -----------------------------------------
of Series E Preferred shall be entitled to convert the same into shares of
Common Stock, he shall surrender the certificate or certificates therefor, duly
endorsed, at the office of the Corporation or of any transfer agent, and shall
give written notice by mail, postage prepaid, to the Corporation at such office
that he elects to convert the same and shall state therein the number of shares
of Series E Preferred being converted and the name or names in which the
certificate or certificates for shares of Common Stock are to be issued.
Thereupon the Corporation shall promptly issue and deliver at such office to
such holder of Series E Preferred or to the nominee or nominees of such holder a
certificate or certificates for the number of shares of Common Stock to which he
shall be entitled. In case the number of shares of Series E Preferred
represented by the certificate or certificates surrendered for conversion
pursuant to this Section A(5) exceeds the number of shares converted, the
Corporation shall, upon such conversion, execute and deliver to the holder at
the expense of the Corporation a new certificate or certificates for the number
of shares of Series E Preferred represented by the certificate or certificates
surrendered which are not to be converted.

               Such conversion shall be deemed to have been made immediately
prior to the close of business on the date of such surrender of the shares of
Series E Preferred to be converted, and the person or persons entitled to
receive the shares of Common Stock issuable upon such conversion shall be
treated for all purposes as the record holder or holders of such shares of
Common Stock on such date notwithstanding that the stock transfer books are
closed or

                                       4


certificates evidencing shares of Common Stock have not been delivered. Any
dividends previously declared but unpaid on shares of Series E Preferred
surrendered for conversion shall be paid in cash contemporaneously with the
issuance of certificates evidencing shares of Common Stock upon the conversion.

               (e)  Adjustment for Stock Splits and Combinations. If the
                    --------------------------------------------
Corporation shall at any time or from time to time after the Original Issue Date
effect a subdivision of the outstanding Common Stock, the Conversion Price then
in effect immediately before that subdivision shall be proportionately
decreased; conversely, if the Corporation shall at any time or from time to time
after the Original Issue Date reduce the outstanding shares of Common Stock by
combination or otherwise, the Conversion Price then in effect immediately before
the combination shall be proportionately increased. Any adjustment pursuant to
this Section A(5)(e) shall become effective at the close of business on the date
the subdivision or combination becomes effective.

               (f)  Adjustment for Certain Dividends and Distributions. In the
                    --------------------------------------------------
event the Corporation at any time or from time to time after the Original Issue
Date shall make or issue, or fix a record date for the determination of holders
of Common Stock entitled to receive, a dividend or other distribution payable in
additional shares of Common Stock, then and in each such event the Conversion
Price for the Series E Preferred then in effect shall be decreased as of the
time of such issuance or, in the event such a record date shall have been fixed,
as of the close of business on such record date, by multiplying the Conversion
Price for the Series E Preferred then in effect by a fraction:

                    (1)  the numerator of which shall be the total number of
               shares of Common Stock issued and outstanding immediately prior
               to the time of such issuance or the close of business on such
               record date; and

                    (2)  the denominator of which shall be the total number of
               shares of Common Stock issued and outstanding immediately prior
               to the time of such issuance or the close of business on such
               record date, plus the number of shares of Common Stock issuable
               in payment of such dividend or distribution; provided, however,
               if such record date shall have been fixed and such dividend is
               not fully paid or if such distribution is not fully made on the
               date fixed therefor, the Conversion Price for the Series E
               Preferred shall be recomputed accordingly as of the close of
               business on such record date and thereafter the Conversion Price
               for the Series E Preferred shall be adjusted pursuant to this
               Section A(5)(f) as of the time of actual payment of such
               dividends or distributions.

               (g)  Adjustments to Dividends and Distributions. In the event the
                    ------------------------------------------
Corporation at any time or from time to time after the Original Issue Date shall
make or issue, or fix a record date for the determination of holders of Common
Stock entitled to receive, a dividend or other distribution payable in
securities of the Corporation other than shares of Common Stock, then and in
each such event provision shall be made so that the holders of Series

                                       5


E Preferred shall receive upon conversion thereof in addition to the number of
shares of Common Stock receivable thereupon, the amount of securities of the
Corporation that they would have received had their Series E Preferred been
converted into Common Stock on the date of such event and had thereafter, during
the period from the date of such event to and including the conversion date,
retained such securities receivable by them as aforesaid during such period
giving application to all adjustments called for during such period under this
Section A(5) with respect to the rights of the holders of the Series E
Preferred.

               (h)  Adjustment for Reclassification, Exchange or Substitution.
                    ---------------------------------------------------------
If the Common Stock issuable upon the conversion of the Series E Preferred shall
be changed into the same or a different number of shares of any class or classes
of stock, whether by capital reorganization, reclassification or otherwise
(other than a subdivision or combination of shares or stock dividend provided
for in sections A(5)(f) and (g) above, or a reorganization, merger,
consolidation or sale of assets provided for in Section A(5)(i) below) then and
in each such event the holder of each share of Series E Preferred shall have the
right thereafter to convert such share into the kind and amounts of shares of
stock and other securities and property receivable upon such reorganization,
reclassification or other change, by holders of the numbers of shares of Common
Stock into which such shares of Series E Preferred might have been converted
immediately prior to such reorganization, reclassification or change, all
subject to further adjustment as provided in this Section A(5).

               (i)  Reorganization, Mergers, Consolidations or Sales of Assets.
                    ----------------------------------------------------------
If at any time or from time to time after the Original Issue Date there shall be
a capital reorganization of the Common Stock (other than a subdivision,
combination, reclassification or exchange of shares provided for elsewhere in
this Section A(5)) or a merger or consolidation of the Corporation in which the
holders of the Common Stock and Preferred Stock of the Corporation immediately
preceding the merger or consolidation do not own 50% or more of the capital
stock of the entity surviving such merger or consolidation or if such capital
stock is not entitled to elect a majority of the directors of the surviving
entity, or the sale, lease, assignment, license, transfer or other conveyance of
all or substantially all the Corporation's properties and assets to any other
person (each a "Reorganization Event"), and if as a part of such Reorganization
Event, the Series E Preferred is not canceled, exchanged, redeemed or otherwise
retired, then provision shall be made so that the holders of the Series E
Preferred shall thereafter be entitled to receive upon conversion of the Series
E Preferred, the number of shares of stock or other securities or property of
the Corporation, or of the successor corporation resulting from such
Reorganization Event, to which a holder of that number of shares of Common Stock
deliverable upon conversion of the Series E Preferred would have been entitled
on such Reorganization Event. In any such case, appropriate adjustment shall be
made in the application of the provisions of this Section A(5) with respect to
the rights of the holders of the Series E Preferred after the Reorganization
Event to the end that the provisions of this Section A(5) (including adjustment
of the Conversion Price then in effect and the number of shares purchasable upon
conversion of the Series E Preferred) shall be applicable after that event as
nearly equivalent as may be practicable. The holders of at least a majority of
the Series E Preferred upon the occurrence of a Reorganization Event shall have
the option of electing on behalf of all of the holders of Series E Preferred
treatment of all shares of Series E Preferred under either this Section A(5)(i)
or Section A(3) hereof, notice of

                                       6


which election shall be submitted in writing to the Corporation at its principal
office no later than ten days before the effective date of such event.

               (j)  Sale of Shares Below Conversion Price.
                    -------------------------------------

                    (1)  If at any time or from time to time after the Original
               Issue Date, the Corporation shall issue or sell Additional Shares
               of Common Stock (as hereinafter defined), other than as a
               dividend as provided in Section A(5)(f) above, and other than
               upon a subdivision or combination of shares of Common Stock as
               provided in Section A(5) (e) above, for a consideration per share
               less than the then existing Conversion Price for the Series E
               Preferred, then and in each such case the then existing
               Conversion Price for the Series E Preferred shall be reduced, as
               of the opening of business on the date of such issue or sale, to
               a price determined by multiplying such Conversion Price by a
               fraction:

                         (A)  the numerator of which shall be (i) the number of
               shares of Common Stock outstanding immediately prior to such
               issue or sale, plus (ii) the number of shares of Common Stock
               that the aggregate consideration received by the Corporation for
               the total number of Additional Shares of Common Stock so issued
               would purchase at such Conversion Price; and

                         (B)  the denominator of which shall be the number of
               shares of Common Stock outstanding immediately prior to such
               issue or sale plus the number of such Additional Shares of Common
               Stock so issued or sold.

                    (2)  For the purpose of making any adjustment in the
               Conversion Price or number of shares of Common Stock purchasable
               on conversion of Series E Preferred as provided above, the
               consideration received by the Corporation for any issue or sale
               of securities shall:

                         (A)  to the extent it consists of cash, be computed at
               the net amount of cash received by the Corporation after
               deduction of any underwriting or similar commissions, concessions
               or compensation paid or allowed by the Corporation in connection
               with such issue or sale;

                         (B)  to the extent it consists of services or property
               other than cash, be computed at the fair market value of such
               services or property as determined in good faith by the board of
               directors; and

                         (C)  if Additional Shares of Common Stock, Convertible
               Securities (as hereinafter defined), or rights or options to
               purchase either Additional Shares of Common Stock or Convertible
               Securities are issued or sold together with other stock or
               securities or other assets of the

                                       7


               Corporation for a consideration that covers both, be computed as
               the portion of the consideration so received that may be
               reasonably determined in good faith by the board of directors to
               be allocable to such Additional Shares of Common Stock,
               Convertible Securities or rights or options.

                    (3)  For the purpose of the adjustment provided in Section
               A(5)(j)(1), if at any time or from time to time after the
               Original Issue Date the Corporation shall issue any rights or
               options for the purchase of, or stock or other securities
               convertible into, Additional Shares of Common Stock (such
               convertible stock or securities being hereinafter referred to as
               "Convertible Securities"), then, in each case, if the Effective
               Price (as hereinafter defined) of such rights, options or
               Convertible Securities shall be less than the then existing
               Conversion Price for the Series E Preferred, the Corporation
               shall be deemed to have issued at the time of the issuance of
               such rights or options or Convertible Securities the maximum
               number of Additional Shares of Common Stock, issuable upon
               exercise or conversion thereof and to have received as
               consideration for the issuance of such shares an amount equal to
               the total amount of the consideration, if any, received by the
               Corporation for the issuance of such rights or options or
               Convertible Securities, plus, in the case of such options or
               rights, the minimum amounts of consideration, if any, payable to
               the Corporation upon exercise or conversion of such options or
               rights.  For purposes of the foregoing, "Effective Price" shall
               mean the quotient determined by dividing the total of all such
               consideration by such maximum number of Additional Shares of
               Common Stock.  No further adjustment of the Conversion Price
               adjusted upon the issuance of such rights, options or Convertible
               Securities shall be made as a result of the actual issuance of
               Additional Shares of Common Stock on the exercise of any such
               rights or options or the conversion of any such Convertible
               Securities.

          If any such rights or options or the conversion privilege represented
by any such Convertible Securities shall expire without having been exercised,
the Conversion Price adjusted upon the issuance of such rights, options or
Convertible Securities shall be readjusted to the Conversion Price that would
have been in effect had an adjustment been made on the basis that the only
Additional Shares of Common Stock so issued were the Additional Shares of Common
Stock, if any, actually issued or sold on the exercise of such rights or
options, or rights of conversion of such Convertible Securities, and such
Additional Shares of Common Stock, if any, were issued or sold for the
consideration actually received by the Corporation upon such exercise, plus the
consideration, if any, actually received by the Corporation for the granting of
all such rights and options, whether or not exercised, plus the consideration
received for issuing or selling the Convertible Securities actually converted
plus the consideration, if any, actually received by the Corporation on the
conversion of such, Convertible Securities.

                                       8


                    (4)  For the purpose of the adjustment provided for in
               Section A(5)(j)(1), if at any time or from time to time after the
               Original Issue Date the Corporation shall issue any rights or
               options for the purchase of Convertible Securities, then in each
               such case, if the Effective Price thereof is less than the then
               existing Conversion Price, the Corporation shall be deemed to
               have issued at the time of the issuance of such rights or options
               the maximum number of Additional Shares of Common Stock issuable
               upon conversion of the total amount of Convertible Securities
               covered by such rights or options and to have received as
               consideration for the issuance of such Additional Shares of
               Common Stock an amount equal to the amount of consideration, if
               any, received by the Corporation for the issuance of such rights
               or options, plus the minimum amounts of consideration, if any,
               payable to the Corporation upon the exercise of such options or
               rights and upon the conversion of such Convertible Securities.
               For the purposes of the foregoing, "Effective Price" shall mean
               the quotient determined by dividing the total amount of such
               consideration by such maximum number of Additional Shares of
               Common Stock.  No further adjustment of such Conversion Price
               adjusted upon the issuance of such rights or options shall be
               made as a result of the actual issuance of the Convertible
               Securities upon the exercise of such rights or options or upon
               the actual issuance of Additional Shares of Common Stock upon the
               conversion of such Convertible Securities.

          The provisions of Section A(5)(j)(3) above for the readjustment of
such Conversion Price upon the expiration of rights or options or the rights of
conversion of Convertible Securities, shall apply mutatis mutandis to the
rights, options and Convertible Securities referred to in this Section 13
(5)(j)(4).

               (k)  Definition. The term "Additional Shares of Common Stock" as
                    ----------
used herein shall mean all shares of Common Stock issued or deemed to be issued
by the Corporation after the Original Issue Date, whether or not subsequently
reacquired or retired by the Corporation, other than (1) shares of Common Stock
issued upon conversion of the Series A Preferred Stock, Series B Preferred
Stock, Series C Preferred Stock, Series D Preferred Stock or Series E Preferred;
(2) up to 6,000,000 shares of Common Stock (as adjusted for any stock dividend,
combination or split with respect to such shares) issued to employees, officers,
directors, consultants or other persons performing services for the Corporation
(if so issued solely because of any such person's status as an officer,
director, employee, consultant or other person performing services for the
Corporation and not as part of any offering of the Corporation's securities)
pursuant to any stock option plan, stock purchase plan, management incentive
plan, consulting agreement or arrangement or other contract or undertaking
approved in the good faith and reasonable judgment of the disinterested members
of the board of directors; and (3) shares issued in the good faith and
reasonable judgment of the disinterested members of the board of directors as
consideration for more favorable interest or rental terms in connection with
equipment leasing or loan transactions approved by the board of directors.

                                       9


               (l)  Accountants' Certificate of Adjustment. In each case of an
                    --------------------------------------
adjustment or readjustment of the Conversion Price for the number of shares of
Common Stock or other securities issuable upon conversion of the Series E
Preferred, the Corporation, at its expense, shall cause independent certified
public accountants of recognized standing selected by the Corporation (who may
be the independent certified public accountants then auditing the books of the
Corporation) to compute such adjustment or readjustment in accordance herewith
and prepare a certificate showing such adjustment or readjustment, and shall
mail such certificate, by first class mail, postage prepaid, to each registered
holder of the Series E Preferred at the holder's address as shown in the
Corporation's books. The certificate shall set forth such adjustment or
readjustment, showing in detail the facts upon which such adjustment or
readjustment is based including a statement of (1) the Conversion Price at that
time in effect for the Series E Preferred, and (2) the number of additional
shares of Common Stock and the type and amount, if any, of other property which
at the time would be received upon conversion of the Series E Preferred.

               (m)  Notices of Record Date. In the event that the Corporation
                    ----------------------
shall propose at any time, or from time to time, to (1) declare any dividend or
distribution upon its Common Stock or Preferred Stock, (2) effect any
reclassification or recapitalization of the Common Stock or Preferred Stock, (3)
reorganize, merge or consolidate the Corporation with or into any other
corporation, (4) sell, lease, assign, license, transfer or otherwise convey all
or substantially all of the assets of the Corporation, (5) dissolve or wind up
the affairs of the Corporation, or (6) offer for sale to the public any shares
of Common Stock, the Corporation shall provide notice to each holder of Series E
Preferred, or if any matter is to be voted on by any stockholder of the
Corporation, the Corporation shall provide notice to each holder of Series E
Preferred, as follows:

                    (1)  with respect to item (1) above, at least 30 days prior
               written notice of the date on which a record shall be taken for
               such dividend or distribution;

                    (2)  with respect to items (2), (3), (4) and (5) above, at
               least 30 days prior written notice of the date on which a record
               shall be taken for determining the right to vote on such matter,
               and, in addition, the date on which the proposed transaction will
               be effective and the date on which the holders of shares of
               Common Stock and Preferred Stock shall be entitled to exchange
               their shares for securities or other property deliverable upon
               the occurrence of the proposed transaction; and

                    (3)  with respect to item (6), at least 30 days prior
               written notice of the date on which shares of Common Stock shall
               be offered to the public; and

                    (4)  with respect to the last item above, at least 30 days
               prior written notice of the date on which a record shall be taken
               for determining the right to vote on such matter.

                                       10


               (n)  Fractional Shares. No fractional Common Stock shall be
                    -----------------
issued upon conversion of Series E Preferred. In lieu of any fractional shares
to which the holder would otherwise be entitled, the Corporation shall pay cash
equal to the product of such fraction multiplied by the fair market value of one
share of the Corporation's Common Stock on the date of conversion, as determined
in good faith by a unanimous vote of the board of directors. Whether or not
fractional shares are issuable upon such conversion shall be determined on the
basis of the total number of shares of Series E Preferred the holder is at the
time converting into Common Stock and the number of shares of Common Stock
issuable upon such conversion.

               (o)  Reservation of Stock Issuable Upon Conversion. The
                    ---------------------------------------------
Corporation shall at all times reserve and keep available out of its authorized
but unissued shares of Common Stock, solely for the purpose of effecting the
conversion of the shares of the Series E Preferred, such number of its shares of
Common Stock as shall from time to time be sufficient to effect the conversion
of all outstanding shares of the Series E Preferred. As a condition precedent to
the taking of any action which would cause an adjustment to the Conversion
Price, the Corporation will take such corporate action as may, in the opinion of
its counsel, be necessary to increase its authorized but unissued shares of
Common Stock to such number of shares as shall be sufficient to enable it to
validly and legally issue the shares of its Common Stock that are issuable based
upon such adjusted Conversion Price.

               (p)  Notices. Any notice required by the provisions of this
                    -------
Section A(5) to be given to the holder of shares of the Series E Preferred shall
be deemed given when received by such holder after the same has been sent by
means of certified mail, return receipt requested, postage prepaid, by a
reputable overnight courier or messenger for hand delivery and addressed to each
holder of record at his address appearing on the books of the Corporation.

               (q)  Payment of Taxes. The Corporation shall pay all taxes and
                    ----------------
other governmental charges (other than taxes measured by the revenue or income
of the holders of the Series E Preferred) that may be imposed in respect of the
issue or delivery of shares of Common Stock upon conversion of the shares of the
Series E Preferred.

               (r)  No Dilution or Impairment. The Corporation shall not amend
                    -------------------------
this Certificate of Designation or participate in any reorganization,
recapitalization, transfer of assets, consolidation, merger, dissolution, issue
or sale of securities or any other voluntary action for the purpose of avoiding
or seeking to avoid the observance or performance of any of the terms to be
observed or performed under this Section A(5) by the Corporation, but will at
all times in good faith assist in carrying out all such action as may be
reasonably necessary or appropriate in order to protect the conversion rights of
the holders of the Series E Preferred against dilution or other impairment.

          6.   Restrictions and Limitations.
               ----------------------------

          So long as 1,750,000 shares of Preferred Stock remain outstanding, the
Corporation shall not, and shall not permit any corporation at least 50% of
whose outstanding voting stock shall at that time be owned directly or
indirectly by the Corporation (a "Subsidiary")

                                       11


to, without the vote or written consent of the holders of a majority of the then
outstanding shares of Preferred Stock:

                    (1)  effect any sale, lease, assignment, license, transfer
               or other conveyance of all or substantially all the assets of the
               Corporation or any of its Subsidiaries, or any reorganization,
               consolidation or merger involving the Corporation or any of its
               Subsidiaries;

                    (2)  effect any liquidation, dissolution or winding up of
               the affairs of the Corporation or any of its Subsidiaries,
               whether voluntary or involuntary, or file any voluntary petition
               in bankruptcy, or file any answer or other pleading seeking any
               reorganization, arrangement, composition, readjustment,
               liquidation or similar relief under any federal or state law
               relative to bankruptcy, insolvency or other relief of debtors, or
               seek, consent to or acquiesce in the appointment of any trustee,
               receiver, conservator or liquidator for any assets of the
               Corporation or any of its Subsidiaries, or any reorganization or
               reclassification of any capital stock of the Corporation or any
               of its Subsidiaries; or

                    (3)  amend the Certificate of Incorporation of the
               Corporation.

          7.   No Reissuance of Preferred Stock.
               --------------------------------

          No share or shares of Series E Preferred acquired by the Corporation
by reason of redemption, purchase, conversion or otherwise shall be reissued,
and all such shares shall be canceled, retired and eliminated from the shares
which the Corporation shall be authorized to issue."

               RESOLVED FURTHER, that the said resolutions of the board of
     directors, and creation and authorization of issuance thereby of said
     series of Series E Preferred Stock, was duly made by the board of directors
     pursuant to authority as aforesaid and in accordance with section 151 of
     the General Corporation Law of the State of Delaware.

                                       12


          IN WITNESS WHEREOF, Maxygen, Inc. has caused this Certificate of
Designations, Preferences and Rights to be signed by the undersigned this 3rd
day of August, 1999.

                                             MAXYGEN, INC.


                                        By:  /s/ Isaac Stein
                                             ------------------------------
                                             Isaac Stein
                                             Chairman