Document:

EXHIBIT 10.6

                            SHAREHOLDER'S AGREEMENT

         THIS  SHAREHOLDER'S  AGREEMENT,  made as of this 1st day of  September,
1990 by and among InforMax,  Inc., a Delaware  corporation (the  "Corporation"),
and Alexander  Titomirov  ("Titomirov"),  Valera Sagitov  ("Sagitov"),  James E.
Bernstein ("Bernstein"),  C. Bowdoin Train ("Train"),  Lewis Hecht ("Hecht") and
Brennan  Klose  ("Klose"),  all of whom are  sometimes  hereinafter  referred to
collectively as the "Shareholders."

                                   WITNESSETH

         WHEREAS, the Corporation has authorized Twenty Thousand (20,000) shares
of common  stock,  in two (2) classes,  the first class  consisting  of Thirteen
Thousand Five Hundred (13,500) shares of voting common stock, par value One Cent
($.01) per share, and the second consisting of Six Thousand Five Hundred (6,500)
shares of non-voting common stock, par value One Cent ($.01) per share;

         WHEREAS,  Titomirov owns Seven Thousand (7,000) voting shares,  Sagitov
owns One Thousand  Five Hundred  (1,500) each of voting and  non-voting  shares,
Train owns One  Thousand  (1,000)  non-voting  shares,  Hecht owns One  Thousand
(1,000)  non-voting  shares,  Klose  owns  Fifty  (50)  non-voting  shares,  and
Bernstein, upon conversion of his Revenue Participation Certificate ("RPC"),

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shall  receive One  Thousand  (1,000)  voting  shares and One  Thousand  (1,000)
non-voting shares;

          WHEREAS,  the Shareholders and the Corporation  desire to make certain
arrangements  with respect to such outstanding  shares (and any shares hereafter
acquired by any Shareholder) and the business and management of the Corporation;

          NOW,  THEREFORE,  in  consideration  of the  promises  and the  mutual
covenants contained herein, the parties agree as follows:

          1.   Definitions.

          As used in this Agreement, the following terms shall have the meanings
set forth in this Section 1:

               (a)   Shares - shares of voting or non-voting common stock of the
Corporation.

               (b)   Bona Fide Offer - a written offer  made in good faith by an
individual or entity,  unrelated to the  Shareholder  receiving  the offer,  and
having  sufficient  financial  resources to purchase the Shares specified in the
offer on the terms stated  therein, provided that (i) the name and residence and
business addresses of the offeror are stated in the offer, and (ii) the offer is
accompanied  by a deposit in the form of a certified  or  cashier's  check in an
amount equal to not less than ten percent (10%) of the proposed purchase price.

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               (c)   Disability - the inability of a Shareholder, due to illness
or injury, to perform at least fifteen (15) eight-hour days of work at an office
outside his home during any six (6) month period.  The date of Disability  shall
be determined in good faith by the Board of Directors of the Corporation.

               (d) Fair Market Value Per Share - the fair market value per Share
shall be determined  as of the date of an event of Separation  (or, in the event
of Separation  due to the death of a  Shareholder,  if the  Corporation  and the
Shareholders  have failed to exercise their option to purchase the Shares of the
deceased  Shareholder  and the eighteen month period during which the estate may
seek a buyer pursuant  hereto has expired,  then the fair market value per Share
shall be determined as of the date that the estate's legal  representative shall
have offered  such Shares to the  Corporation  for purchase  pursuant to Section
5(a)(ii)) by agreement  between the relevant  parties within thirty (30) days of
the effective  notice of such event of Separation (or, in the event of the offer
to the  Corporation  by  the  legal  representative  of a  Shareholder's  estate
described  above,  within thirty (30) days of the effective notice of such offer
to the Corporation), or if such parties cannot agree within such thirty (30) day
period, then by an appraiser approved in good faith by the Board of Directors of
this  Corporation  and  experienced  in  valuations  of companies  substantially
similar  to the  Corporation.  The  determination  of such  appraiser  shall  be
conclusive and binding upon the

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parties  hereto, and shall not be subject to review by any arbitral, judicial or
other tribunal or authority.

               (e)  Family - a Shareholder's spouse, children, parents, siblings
or one or more trusts  established for the exclusive benefit of such Shareholder
and/or one or more of such persons.

               (f)  Separation  -  the  following  events:  Disability,   death,
Termination  For  Cause or any  other  event by which a  Shareholder  ceases  to
perform services for the Corporation.

               (g)  Termination  For Cause - shall mean  termination  for one or
more of the following:

                        (i)   The  commission  of  an  act  of  fraud  upon  the
               Corporation, its directors or shareholders, or any of its clients
               or customers, or the commission of any other act that jeopardizes
               the Corporation's right or ability to operate its business;

                        (ii)  The repeated  failure or refusal of a party hereto
               to perform the legitimate  duties assigned to him by the Board of
               Directors of the Corporation in its reasonable discretion;

                        (iii)  Incompetence,  misconduct  or  negligence in  the
               performance of the legitimate duties and

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               responsibilities  from  time to time  assigned  to a party by the
               Board of Directors in its reasonable discretion;

                        (iv) The conviction of a party for a felony;

                        (v)  The undue  dependency  of  a  party  on  alcohol or
               drugs; or

                        (vi) The material breach of any of the provisions hereof
               by any party hereto.

          2.   Term of Agreement.

          This  Agreement  shall  continue  in full force and  effect  until the
earliest of (i) the date that only one Shareholder owns, directly or indirectly,
all of the Shares,  (ii) the date as of which the  Agreement  is  terminated  by
unanimous written agreement among the Corporation,  those parties hereto who are
shareholders  at the time of such  agreement and Bernstein so long as he has the
right to own Shares upon  conversion of the RPC at the time of such agreement or
(iii)  the  date  on  which  more  than  50% of  the  Corporation's  issued  and
outstanding  Shares have been  registered  under the  Securities Act of 1933, as
amended.  Except as may otherwise by expressly provided herein, upon termination
of this  Agreement,  each  Shareholder  shall  surrender to the  Corporation the
certificates  representing his Shares, and the Corporation shall issue to him in
lieu thereof new certificates which shall

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bear no reference  to  this  Agreement or to any of the restrictions on transfer
set forth herein.

          3.   Voting of Shares.

          Unless Titomirov shall have ceased to own Shares of the  Corporation's
common stock or shall have experienced an event of Separation,  each Shareholder
hereby agrees to vote all voting Shares now or hereafter owned by him, either in
person or by proxy, at each election of directors of the  Corporation,  to elect
Titomirov.  Unless  Bernstein shall have ceased to hold the RPC or any Shares of
the Corporation's common stock into which the RPC has been converted,  or unless
he shall have experienced an event of Separation,  then each Shareholder  hereby
agrees to vote all voting Shares now or hereafter owned by him, either in person
or by  proxy,  at each  election  of  directors  of the  Corporation,  to  elect
Bernstein. Additional directors shall be elected from time to time in accordance
with the By-laws of the Corporation.

          4.   Restrictions on Transfer of Shares.

               (a)  Restrictions.  All  Shares  now  or  hereafter  owned  by  a
Shareholder shall be subject to an option to purchase,  a right of first refusal
and certain restrictions on transfer, all as set forth in this Agreement, and no
Shareholder  shall sell,  assign,  transfer,  pledge or  hypothecate  any Shares
except in accordance with the terms of this Agreement. No Shareholder

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shall  pledge  or  hypothecate  any  Shares  without  the prior  consent  of the
Corporation.  Any sale,  assignment,  transfer,  pledge or  hypothecation of any
Shares in violation of this Agreement shall be void, and the  Corporation  shall
not be obligated either to transfer such Shares on its books or to recognize any
such unauthorized transaction in any manner whatsoever.

               (b) Securities Laws. No Shareholder shall assign, deliver, pledge
or otherwise transfer any Shares, nor will any assignee,  pledgee or endorsee of
any Shares be  recognized as an owner of any Shares by the  Corporation  for any
purpose,  unless a Registration  Statement under the Securities Act of 1933 with
respect to such  Shares  shall then be in effect or unless any such  assignment,
delivery,  pledge  or  transfer  may be  made  without  registration  under  the
Securities Act of 1933, as amended,  and under any applicable  state  securities
laws, and such assignment or transfer will not adversely affect  the  exemptions
from securities  registration on which the Corporation  relied in selling Shares
to the Shareholders, all to the satisfaction of counsel to the Corporation.

               (c) Restrictive  Legend.  Each  certificate  representing  Shares
subject to this Agreement shall contain a legend on the fact thereof  indicating
that  transferability of such stock is restricted and an endorsement on the back
thereof which includes language in substantially the following form:

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                     Any  sale,  pledge  or  other  disposition of the
              shares  of  stock  represented  by this  certificate  is
              restricted by and subject to the terms and provisions of
              the    Shareholders'    Agreement,     dated    as    of
              _________________,   1990,  as  such  Agreement  may  be
              amended from time to time, by and among the Corporation,
              the  holder  of  this   certificate  and  certain  other
              shareholders of the Corporation.

          5.  Option to Purchase Shares.

              (a) Exercise of Option in the Event of Death of a Shareholder.

                     (i)  In  the   event  of  death  of  a   Shareholder,   his
representative shall notify the Corporation and the surviving  Shareholders (the
"Surviving  Shareholders"), within ten (10) days after the  appointment  of such
representative,  that an event of Separation has occurred.  The  Corporation and
the Surviving  Shareholders  shall have the exclusive  option for six (6) months
from the  earlier  of (A) the date  that  notice of  Separation  is given to the
Corporation  and  the  Surviving  Shareholders  by  the  deceased  Shareholder's
representative  or (B) the  date  that the  Corporation  notifies  the  deceased
Shareholder's  representative  that  the  Corporation  is  taking  note  of  the
Separation,   to  purchase   all  (but  not  less  than  all)  of  the  deceased
Shareholder's  Shares in such  proportion as the  Corporation  and the Surviving
Shareholders shall agree. If the Corporation and the Surviving  Shareholders are
unable to so agree, then each Surviving Shareholder who wishes to participate in
such  purchase  shall have  priority  to  purchase  up to that  fraction  of the
deceased.

                                 -8-

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Shareholder's  Shares  in which  the  numerator  is the  number of Shares of the
Corporation's  common  stock  owned  by  such  Surviving   Shareholder  and  the
denominator is the number of Shares of the  Corporation's  common stock owned by
the Surviving  Shareholders  who desire to participate in such purchase.  In the
event  that not all of the  deceased  Shareholder's  Shares  would be  purchased
pursuant to the priority  allocations set forth in the previous  sentence,  then
the Corporation may first elect to purchase up to all of the remaining Shares of
the deceased  Shareholder.  If the Corporation fails to elect to purchase all of
such remaining  Shares,  then the Surviving  Shareholders who desire to purchase
the remaining  Shares shall deliver  written notice to the  Corporation  stating
therein  the number of such  remaining  Shares each such  Surviving  Shareholder
desires to  purchase.  The  remaining  Shares  shall be allocated in one or more
successive  allocations  to those  Surviving  Shareholders  who wish to purchase
additional  Shares and each such  allocation  shall be determined by a fraction,
the  numerator  of which is the  number of Shares  owned by each such  Surviving
Shareholder and the denominator  which is the number of Shares owned by all such
Surviving   Shareholders.   Bernstein   shall  not  be  considered  a  Surviving
Shareholder  for purposes  hereof  unless he shall have first  converted his RPC
into Shares pursuant to the terms thereof; provided, however, that if not all of
the deceased  Shareholder's Shares would be purchased pursuant to the provisions
hereof, then at the Corporation's

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option in its sole discretion Bernstein may elect to purchase any such remaining
Shares. If within fifteen (15) days prior to the expiration of the six (6) month
option  provided  herein the Board of Directors of the  Corporation has not been
reasonably   satisfied   that  all  and  not  less  than  all  of  the  deceased
Shareholder's Shares will be purchased at a single closing pursuant to the terms
hereof,  the  Corporation  may elect to purchase any  remaining  Shares.  If the
Corporation and/or the Surviving  Shareholders fail to tender the purchase price
for all of the Shares  pursuant to the terms  provided in subsection  and (d) of
this Section 5, the option of the Corporation and/or the Surviving  Shareholders
to purchase the deceased Shareholder's Shares shall expire.

                     (ii) In the event that the Corporation and/or the Surviving
Shareholders fail to exercise the option to purchase the deceased  Shareholder's
Shares in  accordance  with  paragraph  (i) of this Section  5(a),  the deceased
Shareholder's  representative shall be free, for a period of up to eighteen (18)
months,  to seek a buyer for the Shares,  subject to the right of first  refusal
provided for in Section 6 hereof. At the end of such eighteen (18) month period,
the  representative  shall offer all of such Shares to the  Corporation  and the
Corporation  shall  purchase all of such Shares.  The price and terms of payment
for such Shares shall be as provided in subjection (d) of this Section 5, except
that the  schedule  of payments of  principal  and  interest to be made over the
applicable five (5) year period

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shall be determined by the Corporation at the time the Corporation purchases the
Shares;  provided,  however,  that the  schedule of payments  of  principal  and
interest  shall  not  be  less  advantageous  to  the  estate  of  the  deceased
Shareholder than is reasonably  practicable for the Corporation  considering the
Corporation's  financial condition at the time of the purchase.  The Corporation
may permit the Surviving Shareholders to participate in any purchase required by
this paragraph  (ii) of this Section 5(a) on the same terms as the  Corporation,
and in such proportion as are consonant with the priority  allocation  mechanism
set forth in paragraph (i) of this Section 5(a).

         (b)   Exercise of Option in the Event of Separation Other Than Death or
               Termination  For Cause Within Two Years of the Effective  Date of
               This Agreement.

                   (i) A  Shareholder  or his  representative  shall  notify the
Corporation,  and the other Shareholders (the "Remaining Shareholders") who have
not been subject to an event of  Separation,  that an event of  Separation  with
respect to such  Shareholder  (other than death or Termination  For Cause within
two years of the effective date of this  Agreement) has occurred within ten (10)
days after such  event,  except  that if such  event (for  example,  Disability)
requires the appointment of a representative for the selling  Shareholder,  such
notice  shall be given  within  ten (10)  days  after  the  appointment  of such
representative. The Corporation and the Remaining Shareholders shall have

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the  exclusive  option for six (6) months  from the earlier of (A) the date that
notice  of  the  Separation  is  given  to the  Corporation  and  the  Remaining
Shareholders by the selling Shareholder or his  representative,  or (B) the date
that the Corporation notifies the selling Shareholder or his representative that
the Corporation is taking note of the occurrence of the event of Separation,  to
purchase all (but not less than all, except in the event of Separation resulting
from  Termination  For  Cause)  of the  selling  Shareholder's  Shares  in  such
proportion as the Corporation and the Remaining Shareholders shall agree. If the
Corporation  and the  Remaining  Shareholders  are unable to so agree,  then the
opportunity  to exercise the option shall be allocated and conducted in the same
manner  as is set forth in  Section  5(a)(i)  above  (including  the  provisions
thereof relating to Bernstein) as if the Remaining  Shareholders  were Surviving
Shareholders.

                   (ii) If the  Corporation,  and/or the Remaining  Shareholders
fail to tender at the  Closing (as that term is defined  below in Section  5(e))
the purchase price for all the Shares of the selling Shareholder pursuant to the
terms provided in Section 5(d) (except in the case of  Termination  For Cause in
which event the option may be  exercised  in respect of any or all of the Shares
of the selling Shareholder),  the option of the Corporation and/or the Remaining
Shareholders  to purchase  the selling  Shareholder's  Shares as a result of the
particular  event of Separation  described in the selling  Shareholder's  notice
shall

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expire.  However, the selling  Shareholder's Shares shall continue to be subject
to the right of first refusal set forth in Section 6 of this Agreement.

          (c)  Exercise  of  Option in the Event of  Separation  Resulting  From
Termination  For Cause.  In the event of Termination  For Cause of a Shareholder
within one year of the effective date of this Agreement,  the Corporation  shall
have the exclusive  option for six (6) months from the date of such  termination
to purchase all of the terminated Shareholder's shares on the terms set forth in
Section 5(d) below. In the event of Termination For Cause of a Shareholder  more
than one  year,  but less  than two  years,  after  the  effective  date of this
Agreement,  the  Corporation  shall have the exclusive  option to purchase fifty
percent (50%) of the terminated  Shareholder's  shares on the terms set forth in
Section 5(d) below, and the remaining fifty percent (50%) of such  Shareholder's
shares shall be subject to the option  described  in Section 5(b) above.  In the
event of  Termination  For Cause of a  Shareholder  more than two years from the
effective date of this Agreement, the Corporation and the Remaining Shareholders
shall  have  the  exclusive  option  for six (6)  months  from  the date of such
termination to purchase any or all of the terminated Shareholder's Shares in the
same manner and on the same terms as are set forth in Section 5(b) above.

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          (d)  Terms of  Payment.  In all  cases  other  than the  Corporation's
exclusive option to purchase all or half (as the case may be) of a Shareholder's
shares as a result of the  Termination  For Cause of a  Shareholder  within  two
years of the  effective  date hereof,  the selling  Shareholder  (or his estate)
shall be entitled to receive the Fair Market  Value Per Share of his Shares.  In
the event of Termination For Cause of a Shareholder  within two (2) years of the
effective date of this Agreement,  the selling  Shareholder shall have the right
to receive from the  Corporation  for those Shares subject to the  Corporation's
exclusive option set forth in Section 5(c) above, not more than the par value of
such  shares as adjusted  from time to time,  all to be paid in cash at one time
upon the  purchase  of such  shares  by the  Corporation.  Except  as  otherwise
provided in  subsection  (a) hereof,  the terms of payment for Shares  purchased
pursuant to subsection (a) and (b) of this Section 5 shall be as follows:

                     (i) Each purchaser shall make a down payment of ten percent
(10%) of the total purchase price of the Shares  purchased by him (not to exceed
One Hundred Thousand ($100,000) Dollars) at the time such Shares are surrendered
(the "Closing"),  and shall simultaneously deliver to the selling Shareholder or
his representative, as the case may be, a negotiable note (the "Note") signed by
the purchaser and payable to the order of the selling Shareholder,  in an amount
equal to the balance of the purchase price of such Shares.  Notwithstanding  the
foregoing,

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to the extent that payment is made out of the proceeds of any applicable key man
insurance  policy  maintained  by  the  Corporation,  the  down  payment  by the
Corporation  shall be not less than the net proceeds of such  policy,  up to the
full amount of the  purchase  price,  and the  Closing  shall be  postponed,  if
necessary,  until such proceeds are received.  Any purchaser  may, in his or its
sole discretion,  increase the amount of his down payment to any amount,  or pay
the entire purchase price at the Closing.

                     (ii) The Note  shall be due and  payable  in not more  than
five (5) equal annual principal  installments,  beginning one (1) year after the
date of the Note.  Interest shall accrue on the unpaid balance of the Note at an
annual  rate equal to the  applicable  federal  rate under  Section  1274 of the
Internal  Revenue Code of 1986,  as amended (or any  successor  provision),  and
shall be  payable  quarterly  beginning  on the  first day of the  fourth  month
following  the date of the Note.  If the  purchaser  fails to pay any amount due
under the Note within thirty (30) days after  written  notice of such default is
given to such purchaser,  the selling  Shareholder  shall have the right, at his
sole  option,  to declare  the entire  unpaid  balance,  together  with  accrued
interest,  immediately  due and  payable.  In the event of default,  the selling
Shareholder  shall also be entitled to collect all reasonable fees and expenses,
including,  but not limited to, reasonable attorneys' fees incurred in enforcing
his rights under the Note. Each such Note shall also provide that the

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purchaser may pre-pay the whole or any part of the remaining  principal  balance
at any time without notice or penalty.

                     (iii) In  conjunction  with the  delivery of the Note,  the
purchaser  shall  execute  and  deliver to the  selling  Shareholder  a security
agreement,   in  a  form  mutually  acceptable  to  the  purchaser  and  selling
Shareholder,  granting to the  selling  Shareholder  a security  interest in the
purchased Shares as security for the Note and providing for the purchased Shares
to be held by an agent designated by the selling  Shareholder  until the Note is
paid in  full.  The  security  agreement  shall  prohibit  any  further  sale or
assignment of the Shares by the purchaser except a sale or assignment that would
result in payment  in full of the Note.  The  purchaser  shall have the right to
exercise all  incidents of  ownership,  including  the right to vote the Shares,
unless the  purchaser is in default  under the Note or the  security  agreement.
Remedies  upon any  default  under the Note shall be as  provided by the Uniform
Commercial Code as enacted in the State of Delaware.

               (e) Delivery of Shares.

                     (i) The  Closing  shall  take place  within sixty (60) days
after  determination  of the Fair Market Value Per Share (or, in the case of the
Corporation's  option to purchase at par value  pursuant to Section  (5)(c),  on
such date as shall be determined  by the Board of Directors of the  Corporation,
but not more

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than six (6) months following the effective date of Termination For Cause), at a
time  and  place  mutually   agreeable  to  the  selling   Shareholder  and  the
purchaser(s).   If  there  is  more  than  one  purchaser  of  the  Shares,  the
consummation  of the  purchases  shall  take place at a single  closing,  to the
extent  reasonably  practicable.  The  Closing  shall be  extended to the extent
reasonably  necessary if the event of Separation  (for example,  death) requires
the appointment of a representative for the Shareholder and such  representative
is unable to effectuate such sale within such sixty-day period.

                     (ii) At the Closing,  the selling Shareholder shall deliver
the Shares to be sold to the  purchaser  or the agent,  as required  pursuant to
subsection  (d)(iii)  of this  Section  5,  free  and  clear  of all  liens  and
encumbrances.  The Shares shall be duly  endorsed for transfer to the  purchaser
and shall be accompanied  by all other documents  necessary for their effective
immediate transfer to the purchaser.

                     (iii) Simultaneously with delivery, the purchaser shall pay
the  purchase  price of the Shares in  accordance  with  subsection  (d) of this
Section 5.

               6. Right of First Refusal.

                     (a) Grant of Right.  No Shareholder  shall sell,  assign or
otherwise transfer all or any portion of his Shares to a

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person who is not a Shareholder  without giving the other  Shareholders  and the
Corporation  a right of first  refusal to purchase such Shares in the manner set
forth in this Section 6.

                     (b)  Purchase by the  Corporation  and Other  Shareholders.
Upon  receiving an offer to purchase any such  Shares,  the selling  Shareholder
shall  require the  offeror to submit a Bona Fide Offer  which such  Shareholder
then shall transmit to the  Corporation and the other  Shareholders  (the "Other
Shareholders"). The Corporation and the Other Shareholders shall have sixty (60)
days  thereafter  in which to purchase all (but not less than all) of the Shares
referred to in the Bona Fide Offer at the same price and terms  contained in the
Bona Fide Offer.  If any or all of the Other  Shareholders  are  exercising  the
right of first refusal hereunder,  each of them shall have the priority right to
purchase  such Shares in such  proportion as the total number of Shares owned by
each  participating  Other  Shareholder shall bear to the total number of Shares
then owned by all participating Other Shareholders; and any of the Shares not so
subscribed for by each participating Other Shareholder shall be allocated in one
or more successive  allocations to those Other Shareholders who wish to purchase
additional  Shares and each such  allocation  shall be determined by a fraction,
the  numerator  of which is the  number  of  shares  owned  by each  such  Other
Shareholder  and the  denominator  of which is the number of Shares owned by all
such Other Shareholders. Bernstein shall not be considered an Other

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Shareholder  for purposes  hereof  unless he shall have first  converted his RPC
into Shares pursuant to the terms thereof; provided, however, that if not all of
the selling  Shareholder's  Shares would be purchased pursuant to the provisions
hereof,  then at the Corporation's  option in its sole discretion  Bernstein may
elect to purchase any such remaining  Shares.  To the extent that the purchasers
fail to tender the full cash purchase price (or to match such other terms as are
contained in the Bona Fide Offer) for all of the Shares  referred to in the Bona
Fide Offer  against the proper  endorsement  and  delivery  of the  certificates
evidencing the Shares within such sixty-day period,  this right of first refusal
shall  expire as to that  particular  Bona Fide Offer,  but shall remain in full
force and effect with  respect to all material  modifications  of that Bona Fide
Offer and all future offers.

                     (c) Purchase by Third Party.  Any Offered  Shares which are
not purchased by the  Shareholders  or the Corporation as provided herein may be
sold to the person,  firm,  association  or  corporation  named in the Bona Fide
Offer,  but not at a lower price, or upon more favorable terms to the purchaser,
then the price and terms set forth in the Bona Fide Offer. Title to such Offered
Shares  shall pass not later than ninety (90) days from the latest date on which
the Other  Shareholders or the  Corporation  have declined or failed to purchase
the Shares. In the event that the selling Shareholder should desire to sell such
Shares at a lower price, or upon terms more favorable to the purchaser, than he

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theretofore offered the Shares to the Other Shareholders or the Corporation,  he
shall,  before he can sell to any such  purchaser,  again  offer  the  Shares in
accordance with the procedure set forth in this Section 6.

               7. Transfer to Family  Members.  Notwithstanding  anything to the
contrary contained herein, each Shareholder shall have the right to transfer all
or any of his  Shares  at any time by will or deed to one or more of his  Family
members  (hereinafter  called  "Close  Assigns").  However,  whenever  any  such
Shareholder  shall thus  dispose of Shares among his Close  Assigns,  such Close
Assigns  and the Shares  owned by them shall  continue to be bound by all of the
terms and conditions of this  Agreement.  Without  limiting the  foregoing,  the
option to purchase  granted in Section 5 and the right of first refusal  granted
in  Section  6 with  reference  to the  Shares  of  such  Shareholder  shall  be
applicable to the Shares of his Close Assigns as if such Shareholder still owned
such Shares.

               8. Transferees of Shares.  Any transferee of Shares (other than a
Close Assign of a Shareholder  as defined in Section 7) who is not a Shareholder
must execute a written  consent to be bound by this Agreement to the same extent
as a Shareholder.  Any such transferee shall be considered a Shareholder for all
purposes  under  this  Agreement;  except  that  no  such  transferee  shall  be
considered a Shareholder whose Shares are subject to the purchase

                                      -20-

<PAGE>
option contained in Section 5 unless such transferee is, or becomes,  engaged by
the Corporation in a managerial or advisory capacity.

         9. Agreement by Corporation.  The Corporation agrees for itself and its
successors and assigns that (i) insofar as is proper or required, it consents to
this Agreement;  (ii) it will not transfer or reissue any Shares in violation of
this  Agreement,  or without  requiring proof of compliance with this Agreement;
and (iii) all other actions required of the Corporation pursuant to the terms of
this Agreement shall be promptly and faithfully performed.

         10.  Departing  Shareholders.  Upon the sale or other  disposition by a
Shareholder  of the  beneficial  ownership  of all of his  Shares,  the  selling
Shareholder  shall  no  longer  be  deemed  to be  either  a party  hereto  or a
"Shareholder"  hereunder,  and shall have no further rights or obligations under
this  Agreement,  except that he shall remain liable to the other parties hereto
for all violations of this  Agreement  committed by him in  connection  with the
disposition of his Shares.

         11. Failure to Surrender  Shares. If a Shareholder or any person having
custody or control of his Shares  fails or refuses to tender  such  Shares as is
required  by the terms of this  Agreement,  all right to vote such  Shares or to
receive dividends or other  distributions with respect thereto shall cease as of
the

                                       21
<PAGE>

time such  Shares  should  have been  surrendered.  The only rights of the owner
thereof  shall be to collect and receive the  purchase  price per Share as above
provided,  and no interest  shall accrue thereon as a result of any delay in the
surrender of such Shares.

         12. Conversion of Non-Voting Shares to Voting Shares. In the event that
Titomirov or the  Corporation  has entered into an agreement or has undertaken a
course of action that results or would result in Titomirov owning or potentially
owning less than fifty-one percent (51%) of the outstanding voting shares of any
class  of the  Corporation,  then,  without  further  action  or  payment by any
Shareholder,  the Corporation shall immediately offer in writing to exchange any
and all  non-voting  Shares held by any  Shareholder  or Close Assign for voting
Shares of the Corporation.  The Corporation and the  Shareholders  agree to take
any action necessary or appropriate to give effect to this provision, including,
but not  limited  to, the taking of any  corporate  actions,  the  execution  of
consents,  the  holding  of  meetings  of  directors  or  shareholders  and  the
preparation, execution and filing or delivery of any  certificates,  as and when
required,  and, in any event,  prior to  Titomirov's  owning less than fifty-one
(51%) of the Corporation's outstanding voting Shares of any class.

                                       22
<PAGE>

     13. Proprietary Information.

         (a) Definitions. The parties acknowledge that each will be furnished or
may  otherwise  receive  or have  access to  information  which  relates  to the
Corporation's past, present or future products, software, research, development,
improvements,  processes, techniques, design or other technical data, customers,
suppliers,  contractors, or regarding administrative,  management, financial, or
marketing activities, or of a third party which provided proprietary information
to one  or  more  of the  parties  hereto  on a  confidential  basis.  All  such
information,  including any materials or documents  containing such information,
are  proprietary  and  confidential  to the disclosing  party (the  "Proprietary
Information").

         (b) Nondisclosure.  Both  during and after the term of this  Agreement,
each party agrees to preserve  and protect the  confidentiality  of  Proprietary
Information  and all  physical  forms  thereof,  whether  disclosed  before this
agreement is signed or afterward.  In addition,  the  receiving  party shall not
disclose or distribute any Proprietary Information to any third party, and shall
not use any  Proprietary  Information  for  his or its  own  benefit  or for the
benefit  of any third  party.  The  foregoing  obligations  shall not apply with
respect to any  Proprietary  Information  the disclosing  party can establish to
have become publicly known without breach of this Agreement.

                                       23
<PAGE>

     (c)  Return of  Proprietary  Information.  Each party  shall  return to the
Corporation  all documents and other  tangibles,  including  diskettes and other
storage media (and  all copies and  reproductions of any of the foregoing) which
contain any Proprietary Information immediately upon request by the Corporation.

         14.  Competition.  During  the term  thereof,  or for a period of three
years  following an Event of Separation of a Shareholder,  or at any time within
two years following the date that a Shareholder no longer owns any Shares,  such
party  will  not,  and such  party  shall  use his  best  efforts  to cause  his
employees,  agents and  affiliates  not to (i) own any interest in,  provide any
financing for or perform any services for, any business or entity which engages,
directly or indirectly,  in  competition in any respect with the  Corporation or
(ii) engage in competition with the Corporation.  Each party further agrees that
during such  period he will not  solicit  any current or former  customer of the
Corporation,  or solicit or employ any current employee of the  Corporation,  or
any contractor of the Corporation providing software  development,  modification
or enhancement services to or for the Corporation.

         15.  Remedies  for  Breach of  Agreement.  Each  Shareholder  agrees as
follows:

              (a) that any breach or attempted  breach by him of the  provisions
of this Agreement could result in irreparable injury

                                       24
<PAGE>

to any or all of the other  parties  hereto for which there would be no adequate
remedy at law;

     (b) that if he should  breach or attempt to breach any such  provisions  of
this  Agreement,  one or  more of the  other  parties  hereto  who are or may be
injured by such breach or attempted  breach may seek  through  process of law to
enjoin him from further breaches or attempted  breaches hereof, or to compel his
compliance  with such  provisions  by specific  performance,  in addition to any
other remedies available in equity or at law; and

     (c)  that if a  court  of  competent  jurisdicition  determines that he has
breached,  or attempted to breach,  any such  provisions of this  Agreement,  he
shall pay all costs and expenses, including, without limitation, court costs and
the reasonable  attorneys' fees,  incurred by the other parties in enforcing his
obligations under this Agreement.

         16.  Notices.  Any and all  notices,  consents or other  communications
provided for herein shall be given in writing and  personally  delivered or sent
by telex,  telecopy,  telegram or other overnight mail with appropriate evidence
of  transmission  or receipt,  or by registered by certified  mail  addressed as
follows:  (i) if to the  Corporation,  to its current office address at the time
such notice,  consent or other  communication  is to be given,  and (ii) if to a
Shareholder,  to  his  most  recent  address  appearing  on the  records  of the
Corporation. Each such notice, consent or

                                       25
<PAGE>
other communication shall be deemed given on the date it is personally delivered
of, if mailed, on the date of mailing.

         17.  Severability.  The  provisions  of this  Agreement shall be deemed
severable,  and the  invalidity or  unenforceability of any  provision shall not
affect the validity or  enforceability of the remainder of this Agreement or any
valid clause of an invalid provision.

         18. Entire Agreement.  This Agreement contains the entire agreement and
understanding  among the parties  hereto with  respect to the matters  contained
herein  and may not be  modified  except  by a written  agreement  signed by the
Corporation  and all of the  other  parties  to  this  Agreement  who  are  then
shareholders of the Corporation.  This Agreement supersedes all prior agreements
or  understandings,  oral or written,  among the parties relating to the subject
matter hereof.

         19.  Corporate  Authorization.  The proper  officers of the Corporation
have been  authorized to enter into this Agreement on behalf of the  Corporation
by a resolution adopted by its board of directors.

         20.  Governing Law;  Consent to  Jurisdiction.  This Agreement shall be
construed  under and  governed in all  respects,  including  issues of validity,
interpretation,  performance  and  enforcement,  by the  laws  of  the  District
Columbia. Each of the parties

                                       26
<PAGE>

hereby  irrevocably  consents to, and waives any  objections to the exercise of,
personal  jurisdiction by the courts in the District of Columbia with respect to
any action or proceeding arising out of this Agreement.

         21. Binding Effect. This Agreement shall inure to the benefit of and be
binding  upon the  Corporation  and its  successors  and  assigns  and upon each
Shareholder and his heirs, legatees,  personal  representatives and assigns, but
neither this Agreement nor any right or obligation hereunder shall be assignable
by any party  without the express  written  consent of all of the other  parties
hereto.

         IN WITNESS  WHEREOF,  the parties have signed this  Agreement as of the
date first written above.

ATTEST:

WITNESSES:                                 Shareholders:

/s/   C. Bowdoin Train                     /s/ Alexander Titomirov
-------------------------------            --------------------------------
                                           Alexander Titomirov

/s/   Alexander Titomirov                  /s/ Valera Sagitov
-------------------------------            --------------------------------
                                           Valera Sagitov

/s/   Alexander Titomirov                  /s/ James E. Bernstein
-------------------------------            --------------------------------
                                           James E. Bernstein

                                       27

<PAGE>
/s/    Alexander Titomirov                 /s/ C. Bowdoin Train
-------------------------------            --------------------------------
                                            C. Bowdoin Train

/s/    Alexander Titomirov                 /s/ Louis Hecht
-------------------------------            --------------------------------
                                           Louis Hecht

/s/    Alexander Titomirov                 /s/ Brennan Klose
-------------------------------            --------------------------------
                                           Brennan Klose

                                           The Corporation:

                                           INFORMAX, INC.

/s/ Peter Van Story                        /s/ Alexander Titomirov
--------------------------------           --------------------------------
Peter Van Story                            Alexander Titomirov
Secretary                                  President

                                       28
<PAGE>

                                 FIRST AMENDMENT
                         TO THE SHAREHOLDERS' AGREEMENT

         THIS FIRST AMENDMENT TO THE  SHAREHOLDERS'  AGREEMENT (the "AMENDMENT")
is made as of 17 August 1999, by and among  Alexander  Titomirov  ("TITOMIROV"),
James  E.  Bernstein   ("BERNSTEIN"),   C.  Bowdoin  Train,  and  Brennan  Klose
(collectively,  the  "CURRENT  SHAREHOLDERS")  and  InforMax,  Inc.,  a Delaware
corporation (the "CORPORATION").

         WHEREAS,   the  Current   Shareholders  are  parties  to  that  certain
Shareholders'  Agreement by and among Valera Sagitov ("SAGITOV") and Louis Hecht
(together with Sagitov, the "FORMER  SHAREHOLDERS"),  the Current  Shareholders,
and the  Corporation  dated as of  September  1, 1990,  as amended  hereby  (the
"SHAREHOLDERS' AGREEMENT");

         WHEREAS,  the  Former  Shareholders  each  ceased  to be a party to the
Shareholders'  Agreement upon the disposition of all of their respective  shares
of the Corporation's common stock;

         WHEREAS,  the  Corporation and FBR Technology  Venture  Partners II, LP
("FBR")  entered into that certain Series A Preferred  Stock Purchase  Agreement
("SERIES A  PREFERRED  STOCK  PURCHASE  AGREEMENT")  dated as of June 22,  1999,
pursuant to which among other things FBR: (a) made an equity investment into the
Corporation,  and (b) entered into that certain  Investor Rights Agreement dated
as of June 22, 1999, by and between FBR and the  Corporation  (together with any
amendments thereto, the "INVESTOR RIGHTS AGREEMENT");

         WHEREAS, pursuant to the terms of the Series A Preferred Stock Purchase
Agreement:  (a)  Vadim  Babenko,  Bernstein  and  Titomirov  (collectively,  the
"FOUNDERS"),  FBR and the  Corporation  entered into that certain Right of First
Refusal and Co-Sale  Agreement,  dated as of June 22,  1999  (together  with any
amendments  thereto,  the "FIRST  REFUSAL AND CO-SALE  AGREEMENT");  and (b) the
Founders,  FBR and the  Corporation  entered into that certain Voting  Agreement
dated as of June 22, 1999  (together with any  amendments  thereto,  the "VOTING
AGREEMENT");

         WHEREAS,  the Current  Shareholders  are desirous of amending the terms
and conditions of the Shareholders' Agreement as set forth herein; and

         WHEREAS,  capitalized  terms used and not defined herein shall have the
meaning ascribed to such terms in the Shareholders' Agreement.

         NOW,  THEREFORE,  in  consideration  of the  above  and for the  mutual
covenants and  agreements  hereinafter  set forth,  the parties  hereto agree as
follows:

         1.       Matters Relating to Section 12.

<PAGE>

                  (a) The parties hereto acknowledge and agree that in the fifth
line of Section 12 of the Shareholders' Agreement the phrase "outstanding voting
shares" shall be corrected to read as follows, "outstanding voting Shares".

                  (b) The parties hereto  acknowledge  and agree that in Section
12 of the  Shareholders'  Agreement the provisions  regarding the  circumstances
pursuant to which nonvoting common stock is automatically  converted into voting
common stock shall only apply when Titomirov no longer has voting control of the
Corporation.

         2.  Amendment  to Section 3. Section 3 of the  Shareholders'  Agreement
shall be amended to add as the last sentence of Section 3, the following:

                   Notwithstanding  anything to the contrary  herein,  including
         this  Section 3, each  Shareholder  shall take all action  necessary in
         order to carry out the intents and purposes of the Voting Agreement.

         3.  Amendment  to Section 5. Section 5 of the  Shareholders'  Agreement
shall be amended to add a new subsection (f) which shall read in its entirety as
follows:

                   (f)   Notwithstanding   anything  to  the  contrary   herein,
         including  this  Section  5,  each   Shareholder  and  the  Corporation
         acknowledges  and agrees  that any rights of first  refusal  granted to
         such  Shareholders or the Corporation,  as the case may be, pursuant to
         this  Section 5, shall be  subject to the rights of first  refusal  and
         co-sale  granted  to FBR  pursuant  to the  terms of the Right of First
         Refusal and Co-Sale  Agreement as set forth and limited by the terms of
         such Right of First Refusal and Co-Sale Agreement.

         4.  Amendment  to Section 7. Section 7 of the  Shareholders'  Agreement
shall be amended to add as the last sentence to Section 7, the following:

                   Notwithstanding  anything to the contrary  herein,  including
         this  Section 7, each Founder  acknowledges  and agrees that any rights
         conferred  upon such  Founder  pursuant  to this  Section  7,  shall be
         exercised by such Founder in a manner  consistent  with the limitations
         on such rights provided for in the First Refusal and Co-Sale Agreement.

         5. Amendment to Section 14. Section 14 of the  Shareholders'  Agreement
is hereby amended in its entirety to read as follows:

                  14.      Noncompetition.

                           (a) Covenants.  During the term of this Agreement and
         for a period  of twenty  four (24)  months  after  termination  of this
         Agreement (the "Noncompetition Period"), no Shareholder shall, directly
         or indirectly, as an officer, director,  employee,  consultant,  owner,
         shareholder,  adviser,  joint venturer, or otherwise,  compete with the
         Company Business. This covenant

                                       2
<PAGE>

         shall not preclude a Shareholder from owning less than two percent (2%)
         of  the  securities  of  any  competitor  of the  Corporation  if  such
         securities  are  publicly  traded  on  a  nationally  recognized  stock
         exchange or  over-the-counter  market. For purposes of this Section 14,
         the term "Company  Business"  shall mean the business of developing and
         licensing pharma-informatic software tools of the type developed by the
         Corporation.

                           (b)  Acknowledgments.  Each Shareholder  acknowledges
         that the foregoing  restriction on competition is fair and  reasonable,
         given  the  scope  of the  Company  Business  and  the  nature  of such
         Shareholder's  relationship  with  the  Corporation.  Each  Shareholder
         acknowledges  that such  Shareholder has had, and will have,  access to
         information  that  would be  valuable  or useful  to the  Corporation's
         competitors, and therefore acknowledges that the foregoing restrictions
         on such  Shareholders'  future  employment and business  activities are
         fair and reasonable.  Each Shareholder acknowledges and is prepared for
         the  possibility  that such  Shareholder's  standard  of living  may be
         reduced during the  Noncompetition  Period, and assumes and accepts any
         risk associated with that possibility.

         6. Waiver of Rights. Each Shareholder and the Corporation  acknowledges
and  agrees  that  this  Amendment  constitutes  a  waiver  of any  rights  such
Shareholder or the  Corporation has pursuant to the  Shareholders'  Agreement to
the extent any such rights are  inconsistent  with the First Refusal and Co-Sale
Agreement, the Investor Rights Agreement or the Voting Agreement.

         7.  Scope of  Amendment.  Except  as  expressly  modified  hereby,  the
Shareholders'  Agreement is hereby  ratified and confirmed and shall continue in
full force and effect.

             [THE REMAINDER OF THIS PAGE INTENTIONALLY LEFT BLANK]

                                       3
<PAGE>

         IN  WITNESS  WHEREOF,  each of the  parties  hereto has  executed  this
Amendment to the  Shareholders'  Agreement  or has caused this  Amendment to the
Shareholders'  Agreement to be duly  executed  and  delivered in its name on its
behalf, all as of the day and year first written above.

CURRENT SHAREHOLDERS:

/s/ Alexander Titomirov                   /s/ C. Bowdoin Train
------------------------------            ---------------------------------
Alexander Titomirov                       C. Bowdoin Train

/s/ James E. Bernstein
------------------------------            ---------------------------------
James E. Bernstein                        Brennan Klose

                                          THE CORPORATION: INFORMAX, INC.

                                          /s/ Alexander Titomirov
                                          ---------------------------------
                                          Alexander Titomirov
                                          President and Chief Executive Officer

                                       4
<PAGE>

                                 SECOND AMENDMENT

                         TO THE SHAREHOLDERS' AGREEMENT

     THIS SECOND AMENDMENT TO THE  SHAREHOLDERS'  AGREEMENT (the "AMENDMENT") is
made as of March 29, 2000, by and among Alexander Titomirov ("TITOMIROV"), James
E. Bernstein ("BERNSTEIN"),  C. Bowdoin Train ("TRAIN"), Brennan Klose ("KLOSE";
collectively  with Titomirov,  Bernstein and Train, the "CURRENT  SHAREHOLDERS")
and InforMax,  Inc., a Delaware corporation (the "CORPORATION") and WPG Software
Fund, L.P., WPG Raytheon Software Fund, L.P., WPG  Institutional  Software Fund,
L.P.,  WPG  Networking  Fund,  L.P.,  WPG Raytheon  Networking  Fund,  L.P., WPG
Institutional Networking Fund, L.P., and Raj Mehra (the "BUYERS").

         WHEREAS,   the  Current   Shareholders  are  parties  to  that  certain
Shareholders'  Agreement by and among Valera Sagitov ("Sagitov") and Louis Hecht
(together with Sagitov, the "FORMER  SHAREHOLDERS"),  the Current  Shareholders,
and the  Corporation  dated as of  September  1, 1990,  as amended  hereby  (the
"SHAREHOLDERS' AGREEMENT");

         WHEREAS,  the  Former  Shareholders  each  ceased  to be a party to the
Shareholders'  Agreement upon the disposition of all of their respective  shares
of the Corporation's common stock;

         WHEREAS,  the Current  Shareholders,  FBR  Technology  Venture  Capital
Managers, Inc. ("FBR") and the Corporation entered into that certain Side Letter
Agreement,  dated June 22, 1999, pursuant to which the Current  Shareholders and
the   Corporation   subordinated   their  rights  of  first  refusal  under  the
Shareholders'  Agreement  regarding transfers of Shares to the rights granted to
FBR pursuant to that certain Right of First Refusal and Co-Sale  Agreement dated
as June 22, 1999, by and among FBR, the  Corporation,  the Current  Shareholders
and Vadim Babenko ("BABENKO");

         WHEREAS, Titomirov and Babenko and the Buyers entered into that certain
Stock Purchase  Agreement  ("STOCK  PURCHASE  Agreement")  dated as of March 29,
2000,  pursuant to which,  among other  things,  (a)  Titomirov and Babenko have
exercised  options (the  "OPTIONS") to purchase in the aggregate  750,000 shares
from the Corporation  (the "OPTION  SHARES") for an aggregate  purchase price of
Three  Hundred  Seventy-Five  Thousand  Dollars  ($375,000);   (b)  Babenko  and
Titomirov  exercised the Options on the  understanding  that the Corporation and
the other  Current  Shareholders  would  enter into this  Amendment;  (c) Buyers
entered  into  the  Stock  Purchase  Agreement  on the  understanding  that  the
Corporation and the other Current Shareholders would enter into this Amendment;

         WHEREAS,  the Buyers and the Current  Shareholders  are desirous of the
Buyers joining the Shareholder's Agreement for purposes Section 6 and Section 12
of the Shareholders' Agreement only;

         WHEREAS,  the Current  Shareholders  are desirous of amending the terms
and conditions of the Shareholders' Agreement as set forth herein;

<PAGE>
         WHEREAS,  the parties have agreed that Buyers' right  hereunder will be
subordinate to the rights of FBR under the First Refusal and Co-Sale  Agreement;
and

         WHEREAS,  capitalized  terms used but not defined herein shall have the
meaning ascribed to such terms in the Shareholders' Agreement.

         NOW,  THEREFORE,  in  consideration  of the  above  and for the  mutual
covenants and  agreements  hereinafter  set forth,  the parties  hereto agree as
follows:

         1.       Matters Relating to Section 6.
                  -----------------------------

                  (a) The parties hereto  acknowledge  and agree that the Buyers
are a party to the  Shareholder's  Agreement  for all purposes of Section 6, and
shall be a  "Shareholder"  for purposes of Section 6, and that the first line of
Section  6(a) of the  Shareholders'  Agreement  shall be  amended to read in its
entirety as follows:

                   Except for the Buyers,  no Shareholder  shall sell, assign or
otherwise  transfer  all or any  portion  of his Shares to a person who is not a
Shareholder without giving the other Shareholders, including the Buyers, and the
Corporation  a right of first  refusal to purchase such Shares in the manner set
forth in this Section 6.

                  (b) The parties  hereto  acknowledge  and agree that the first
line of Section 6(b) of the  Shareholders'  Agreement shall be corrected to read
as follows:

                  Upon  receiving  an offer to  purchase  any such  Shares,  the
selling  Shareholder shall require the offeror to submit a Bona Fide Offer which
such   Shareholder  then  shall  transmit  to  the  Corporation  and  the  Other
Shareholders, including the Buyers (the "Other Shareholders").

                  (c)  The  parties  hereto   acknowledge  and  agree  that  all
remaining  provisions  of Section 6 of the  Shareholders'  Agreement  are hereby
ratified and confirmed and shall continue in full force and effect.

         2.       Matters Relating to Section 12.

                  (a) The parties hereto  acknowledge  and agree that the Buyers
are a party to the  Shareholder's  Agreement  for purposes of all of Section 12,
and shall be a "Shareholder" for purposes of Section 12, and that the first line
of Section  12 of the  Shareholders'  Agreement  shall be amended to read in its
entirety as follows:

                  In the event  Titomirov or the Corporation has entered into an
agreement  or has  undertaken a course of action that results or would result in
Titomirov owning or potentially  owning less than fifty-one percent (51%) of the
outstanding  voting Shares of the Corporation,  then,  without further action or
payment  by  any  Shareholder,  including  the  Buyers,  the  Corporation  shall
immediately  offer in writing to exchange any and all non-voting  Shares held by
any Shareholder,  including the Buyers, or Close Assign for voting Shares of the
Corporation.

                                       2
<PAGE>

                  (b)  The  parties  hereto   acknowledge  and  agree  that  all
remaining  provisions  of Section 12 of the  Shareholders'  Agreement are hereby
ratified and confirmed and shall continue in full force and effect.

         3.  Scope of  Amendment.  Except  as  expressly  modified  hereby,  the
Shareholders'  Agreement is hereby  ratified and confirmed and shall continue in
full force and effect.

         4.  Joinder to Side  Letter.  (a) The Buyers are hereby made a party to
the Side Letter as a "Principal Shareholder"  thereunder,  and the Buyers hereby
agree  to be bound by all the  terms  and  conditions  of the Side  Letter  as a
"Principal Shareholder" thereunder.

                  (b)  The  Buyers  represent  and  warrant individually  to the
Company and the other Principal  Shareholders  and FBR that each Buyer:  (a) has
reviewed  the Side  Letter  (as  attached  hereto),  and fully  understands  all
provisions of the Side Letter, and (b) has become a Principal  Shareholder under
the Side Letter and is bound by all the terms and  conditions of the Side Letter
with the same  effect as though  the Buyer was a  subscribing  party to the Side
Letter.

                  (c)  All   references   in  the  Side  Letter  to   "Principal
Shareholder" or "Principal Shareholders" shall be deemed to include the Buyer.

                  (d) Except as provided herein, all of the terms and conditions
of the Side Letter are  unmodified  and shall  continue in full force and effect
and shall be binding  upon the parties  hereto and their  respective  assigns in
accordance with the terms thereof.

         5.  Counterparts.   This  Amendment  may  be  executed   (including  by
facsimile)  in one or more  counterparts,  each of  which  shall  be  deemed  an
original but all of which together will constitute one and the same instrument.

              [THE REMAINDER OF THIS PAGE INTENTIONALLY LEFT BLANK]

                                       3
<PAGE>

                  IN WITNESS  WHEREOF,  each of the parties  hereto has executed
this First  Amendment  to the  Shareholders'  Agreement or has caused this First
Amendment to the  Shareholders'  Agreement to be duly  executed and delivered in
its name on its behalf, all as of the day and year first written above.

CURRENT SHAREHOLDERS:

/s/ Alexander Titomirov                       /s/ C. Bowdoin Train
-----------------------------                 ----------------------------------
Alexander Titomirov                           C. Bowdoin Train

/s/ James E. Bernstein
-----------------------------                 ----------------------------------
James E. Bernstein                            Brennan Klose

                                              THE CORPORATION:

                                              INFORMAX, INC.

                                              By: /s/ Joe Lehnen
                                                  ------------------------------
                                                  Joe Lehnen
                                                  Chief Financial Officer

                                              BUYERS:

                                              WPG SOFTWARE FUND, L.P.,
                                              BY ITS GENERAL PARTNER

                                              By: /s/ Benjamin Taylor BT/RM
                                                  ------------------------------
                                                  Benjamin Taylor, in his
                                                  individual capacity

                                              WPG RAYTHEON SOFTWARE FUND,
                                              L.P., BY ITS GENERAL PARTNER

                                              By:  /s/ Benjamin Taylor BT/RM
                                                   -----------------------------
                                                   Benjamin Taylor, in his
                                                   individual capacity

<PAGE>

                                              WPG INSTITUTIONAL SOFTWARE
                                              FUND, L.P., BY ITS GENERAL PARTNER

                                              By: /s/ Benjamin Taylor BT/RM
                                                  ------------------------------
                                                  Benjamin Taylor, in his
                                                  individual capacity

                                              WPG NETWORKING FUND, L.P., BY ITS
                                              GENERAL PARTNER

                                              By: /s/ Raj Mehra
                                                  -----------------------------
                                                  Raj Mehra, in his
                                                  individual capacity

                                              WPG RAYTHEON NETWORKING
                                              FUND, L.P., BY ITS GENERAL PARTNER

                                              By: /s/ Raj Mehra
                                                  -----------------------------
                                                  Raj Mehra, in his
                                                  individual capacity

                                              WPG INSTITUTIONAL NETWORKING
                                              FUND, L.P., BY ITS GENERAL PARTNER

                                              By: /s/ Raj Mehra
                                                  -----------------------------
                                                  Raj Mehra, in his
                                                  individual capacity

                                              RAJ MEHRA

                                              By: /s/ Raj Mehra
                                                  ------------------------------EXHIBIT 10.7

                                                                  EXECUTION COPY
                                                                  --------------

                                 LOAN AGREEMENT

         THIS LOAN  AGREEMENT (this "AGREEMENT"),  is entered  into as of May 6,
1999, between INFORMAX,  INC., a Delaware corporation (the "BORROWER"),  and PNC
BANK,  NATIONAL  ASSOCIATION  (the "BANK").  The Borrower and the Bank, with the
intent to be legally bound, agree as follows:

1.   LOAN. The following loan and credit facilities (collectively referred to as
     the "FACILITY"), shall be subject to and governed by this Agreement:

     $800,000 Secured Revolving Credit ("REVOLVING CREDIT")

     $200,000 Equipment Line of Credit ("EQUIPMENT LINE")

The maximum  available amount of the Facility shall be $1,000,000.  The proceeds
of the Revolving Credit shall be used for general  corporate and working capital
purposes.  The  proceeds  of the  Equipment  Line  shall  be used  only  for the
acquisition of computer and telecommunications equipment.

2.   TERMS  AND  CONDITIONS.  Subject  to the terms and  conditions  hereof  and
     relying upon the  representations and warranties herein set forth, the Bank
     agrees to make  advances  under the  Facility  (each an  "ADVANCE")  to the
     Borrower  at any time or from time to time on or after  the date  hereof in
     accordance with the terms of this Agreement.

     The Facility  shall consist of the components set forth in Section 1 hereof
     in accordance with the following terms:

     2.1    EXPIRATION DATE.

            (a) Revolving  Credit:  Three hundred sixty four (364) days from the
            date of the closing of this Agreement  ("CLOSING  DATE"), or on such
            subsequent anniversary of the Closing Date as the parties hereto may
            agree (the "REVOLVING CREDIT EXPIRATION DATE").

            (b) Equipment  Line:  All advances  under the Equipment Line must be
            requested  and made  within the three  hundred  sixty four (364) day
            period  immediately  following the Closing Date (the "EQUIPMENT LINE
            EXPIRATION DATE"). Six months from the Closing Date (the "FIRST TERM
            LOAN CONVERSION  DATE") all Equipment Line advances then outstanding
            will  convert  into a term  loan (the  "FIRST  TERM  LOAN").  On the
            Equipment  Line  Expiration  Date,  all Equipment Line advances made
            since the First Term Loan Conversion Date shall be converted into
<PAGE>

            a second term loan (the "SECOND TERM LOAN").  Each of the First Term
            Loan and the  Second  Term  Loan  shall  provide  for  repayment  of
            principal   and   interest  in  twenty   four  (24)  equal   monthly
            installments.

     2.2    INTEREST RATES.

            (a) Revolving Credit:  the Prime Rate (as defined  hereinafter) plus
            1.50% per annum;  the "PRIME RATE" shall be the rate of interest per
            annum  announced by the Bank from time to time as its "PRIME  RATE;"
            it is a base rate upon  which  other  rates  charged by the Bank are
            based, and is not necessarily the best rate offered by the Bank.

            (b) Equipment Line: the Prime Rate plus 1.75% per annum

     2.3    FACILITY FEE. The Borrower shall pay to the Bank a one-time facility
            fee in an amount equal to .75% of the maximum amount of the Facility
            ($7,500), payable on the Closing Date.

     2.4    BORROWING BASE/AVAILABILITY.

            (a) Revolving  Credit:  the  Revolving  Credit shall be available in
            amounts  determined in accordance  with the Borrowing  Base Rider in
            the form attached hereto as Exhibit A.

            (b) Equipment  Line.  (i) no Advances  shall be available  under the
            Equipment  Line  until the  earlier of (A) the  consummation  by the
            Borrower  of a new round of equity  financing  which  results in net
            proceeds  to  the   Borrower   of  at  least  One  Million   Dollars
            ($1,000,000);  and (B)  certification  by the  Borrower  that it has
            attained a Tangible Net Worth,  calculated in accordance  with GAAP,
            consistently applied, of at least Two Hundred Fifty Thousand Dollars
            ($250,000);

            (ii) Advances  under the  Equipment  Line shall be limited to 80% of
            the face amount of equipment invoices (excluding taxes, shipping and
            installation)  submitted with any Advance Request (as provided below
            in Section 2.5), not to exceed $200,000 in the aggregate.

     2.5    REQUESTS. Except as otherwise provided herein, the Borrower may from
            time to time prior to the Revolving  Credit  Expiration Date, or the
            Equipment Line Expiration  Date, as applicable,  request the Bank to
            make an advance  under the  Revolving  Credit or  Equipment  Line by
            delivering to the Bank, not later than 12:00 Noon,  Eastern Standard
            time, a request by telephone by the Chief  Executive  Officer of the
            Borrower  immediately  confirmed in writing by letter,  facsimile or
            telex from the Chief Executive  Officer of the Borrower (an "ADVANCE
            REQUEST"),  it  being  understood  that  the  Bank  may  rely on the
            authority of such officer making

                                       2
<PAGE>

            such a telephonic  request  without the necessity of receipt of such
            written confirmation.  Each Advance Request shall be irrevocable and
            shall specify (a) the proposed borrowing date; and (b) the aggregate
            amount of the proposed borrowing  hereunder.  If the Advance Request
            is made under the Revolving  Credit,  it shall be accompanied by the
            most recent Borrowing Base Certificate prepared by the Borrower.  If
            the Advance  Request is made under the  Equipment  Line, it shall be
            accompanied by invoices for equipment acquisitions.

     2.6    PROMISSORY  NOTES.  The  obligation  of the  Borrower  to repay  the
            aggregate unpaid principal amount of the Revolving Credit,  together
            with interest  thereon,  shall be evidenced by a promissory  note of
            the Borrower  ("REVOLVING  CREDIT NOTE") payable to the order of the
            Bank in a face amount equal to the maximum  amount of the  Revolving
            Credit. The obligation of the Borrower to repay the aggregate unpaid
            principal  amount of the  Equipment  Line,  together  with  interest
            thereon,  shall be evidenced  by a  promissory  note of the Borrower
            ("TERM  NOTE")  payable  to the  order of the Bank in a face  amount
            equal to the maximum  amount of the  Equipment  Line.  The Revolving
            Credit Note and the Term Note shall be  referred to together  herein
            as the "NOTES."

     2.7    LOCKBOX. If an Event of Default (as hereinafter defined) occurs, and
            the same is not cured  subject to any  applicable  cure period,  the
            Bank may require,  in its sole  discretion,  the  establishment of a
            lockbox at the Bank to which account  debtors of the Borrower  would
            submit  all   payments  in  respect  of  the   Borrower's   accounts
            receivable.

3.   SECURITY.  The security for repayment of the Facility shall include but not
     be limited to the collateral,  guaranties and other  documents  heretofore,
     contemporaneously  or  hereafter  executed  and  delivered to the Bank (the
     "SECURITY  DOCUMENTS"),  which shall secure repayment of the Facility,  the
     Notes and all  other  loans,  advances,  debts,  liabilities,  obligations,
     covenants  and  duties  owing  by the  Borrower  to the Bank of any kind or
     nature,  present or future,  whether or not evidenced by any note, guaranty
     or other  instrument,  whether  arising under any agreement,  instrument or
     document,  whether  or not for the  payment  of money,  whether  arising by
     reason of an  extension of credit,  opening of a letter of credit,  loan or
     guarantee or in any other  manner,  whether  arising out of  overdrafts  on
     deposit or other accounts or electronic  funds transfers  (whether  through
     automatic clearing houses or otherwise) or out of the Bank's non-receipt of
     or  inability  to  collect  funds or  otherwise  not  being  made  whole in
     connection  with depository  transfer check or other similar  arrangements,
     whether  direct or indirect  (including  those  acquired by  assignment  or
     participation),  absolute or contingent, joint or several, due or to become
     due, now existing or hereafter  arising,  and any  amendments,  extensions,
     renewals or increases  and all costs and  expenses of the Bank  incurred in
     the documentation,  negotiation,  modification,  enforcement, collection or
     otherwise  in  connection  with  any of the  foregoing,  including  but not
     limited to reasonable attorneys' fees and expenses (hereinafter referred to
     collectively as the "OBLIGATIONS"). Unless expressly provided to

                                       3
<PAGE>

     the  contrary  in  documentation  for any other  loan or  loans,  it is the
     express intent of the Bank and the Borrower that all Obligations  including
     those included in the Facility be cross-collateralized and cross-defaulted,
     such that collateral securing any of the Obligations shall secure repayment
     of all  Obligations  and a default under any Obligation  shall be a default
     under all Obligations.  This Agreement (including the Addendum),  the Notes
     and the  Security  Documents  are  collectively  referred  to as the  "LOAN
     DOCUMENTS".

4.   REPRESENTATIONS  AND  WARRANTIES.  The Borrower  hereby makes the following
     representations  and warranties,  which shall be true and correct as of the
     date of this Agreement and the date of the making of an Advance,  and which
     shall be true and correct  except as  otherwise  set forth on the  Addendum
     attached hereto and incorporated herein by reference (the "ADDENDUM").

     4.1.   EXISTENCE,  POWER AND  AUTHORITY.  The  Borrower is duly  organized,
            validly existing and in good standing under the laws of Delaware and
            has the corporate  power and authority to own and operate its assets
            and to conduct  its  business  as now or  currently  proposed  to be
            carried on, and is duly qualified,  licensed and in good standing to
            do business in all jurisdictions  where its ownership of property or
            the nature of its business requires such qualification or licensing,
            except where the failure to be so  qualified  or licensed  would not
            have a  material  adverse  effect on (a) the  business,  operations,
            property,  condition  (financial  or  otherwise) or prospects of the
            Borrower or (b) the validity or  enforceability of this Agreement or
            any of the other Loan  Documents  or the rights or  remedies  of the
            Bank  hereunder or thereunder  (a "MATERIAL  ADVERSE  EFFECT").  The
            Borrower  is  duly  authorized  to  execute  and  deliver  the  Loan
            Documents,  its Board of Directors has taken all necessary action to
            authorize the execution and delivery of the Loan Documents,  and the
            Borrower is and will continue to be duly  authorized to borrow under
            this  Agreement and to perform all of the other terms and provisions
            of the Loan Documents.

     4.2.   FINANCIAL  STATEMENTS.  The Borrower  has  delivered or caused to be
            delivered its most recent balance sheet and income statement for the
            fiscal  year ended  December  31,  1998 (the  "HISTORICAL  FINANCIAL
            STATEMENTS"). The Historical Financial Statements are true, complete
            and  accurate  in all  material  respects  and  fairly  present  the
            financial  condition,  assets  and  liabilities,   whether  accrued,
            absolute,  contingent or otherwise and the result of the  Borrower's
            operations  for  the  period  specified   therein.   The  Historical
            Financial Statements have been prepared in accordance with generally
            accepted accounting  principles ("GAAP")  consistently  applied from
            period to period subject in the case of interim statements to normal
            year-end  adjustments  and to  items  that  would  be  disclosed  in
            footnotes to audited statements.

     4.3.   NO  MATERIAL  ADVERSE  CHANGE.  Since  the  date  of the  Historical
            Financial  Statements,  the  Borrower  has not suffered any material
            damage  to,  destruction  or loss of,  its  assets,  and no event or
            condition has occurred or exists, which has

                                       4
<PAGE>

            resulted or, to Borrower's  knowledge,  could reasonably be expected
            to result in a  material  adverse  change in its  business,  assets,
            operations, financial condition or result of operation.

     4.4.   BINDING OBLIGATIONS. The Loan Documents, when executed and delivered
            by the  Borrower,  will  constitute  the  legal,  valid and  binding
            obligations  of the Borrower  enforceable  in accordance  with their
            terms  except  as  enforceability   may  be  limited  by  applicable
            bankruptcy,  reorganization,  moratorium  and  other  laws,  now  or
            hereafter in effect,  affecting the enforcement of creditor's rights
            generally  and  that   enforceability  may  be  limited  by  general
            principles of equity.

     4.5.   NO DEFAULTS OR VIOLATIONS. There does not exist any Event of Default
            under this  Agreement  or any  material  default or violation by the
            Borrower of or under any of the terms, conditions or obligations of:
            (i) its certificate of  incorporation  or bylaws;  (ii) any material
            indenture,  mortgage,  deed of trust, franchise,  permit,  contract,
            agreement, or other instrument to which it is a party or by which it
            is bound; or (iii) any law, regulation,  ruling, order,  injunction,
            decree,   condition  or  other  requirement  of  a  material  nature
            applicable  to or imposed  upon it by any law,  or the action by any
            court or any  governmental  authority or agency against the Borrower
            or its assets.  The  consummation of the  transactions  set forth in
            this Agreement will not result in any such default or violation.

     4.6.   TITLE  TO  ASSETS.  The  Borrower  has  valid  title  to the  assets
            reflected on the Historical Financial Statements,  free and clear of
            all  liens  and  encumbrances,  except  for (i)  current  taxes  and
            assessments not yet due and payable, (ii) liens and encumbrances, if
            any,  reflected  or noted in the  Historical  Financial  Statements,
            (iii) assets  disposed of by the Borrower in the ordinary  course of
            business since the date of the Historical Financial Statements, (iv)
            those liens or encumbrances specified on the Addendum, (v) liens and
            encumbrances   permitted   by   Section   6.2  and  (vi)  liens  and
            encumbrances under the Loan Documents.

     4.7.   LITIGATION. There are no actions, suits, proceedings or governmental
            investigations  pending or, to the best of the Borrower's knowledge,
            threatened against the Borrower,  which could reasonably be expected
            to result in a  material  adverse  change in its  business,  assets,
            operations,  financial  condition or results of operations and there
            is no basis known to the Borrower for any action, suit,  proceedings
            or governmental  investigation which could reasonably be expected to
            result in such a material adverse change.  All pending or threatened
            litigation  against the Borrower of which  Borrower has knowledge is
            listed on the Addendum.

     4.8.   TAX RETURNS. The Borrower has filed all returns and reports that are
            required to be filed by it in connection with any federal,  state or
            local tax, duty or charge levied, assessed or imposed upon it or its
            property or withheld by it, including

                                       5
<PAGE>

            unemployment,  social  security and similar  taxes,  and all of such
            taxes have been either paid or adequate  reserve or other  provision
            has been made.

     4.9.   EMPLOYEE  BENEFIT PLANS.  Each employee benefit plan as to which the
            Borrower may have any  liability  complies in all material  respects
            with all  applicable  provisions of the Employee  Retirement  Income
            Security  Act  of  1974   ("ERISA"),   including   minimum   funding
            requirements,  and (i) no Prohibited  Transaction  (as defined under
            ERISA)  has  occurred  with  respect  to  any  such  plan,  (ii)  no
            Reportable  Event (as  defined  under  Section  4043 of  ERISA)  has
            occurred with respect to any such plan which would cause the Pension
            Benefit Guaranty Corporation to institute  proceedings under Section
            4042 of ERISA,  (iii) the Borrower has not  withdrawn  from any such
            plan or initiated  steps to do so, and (iv) no steps have been taken
            to terminate any such plan.

     4.10.  ENVIRONMENTAL  MATTERS.  The  Borrower  is  in  compliance,  in  all
            material respects,  with all Environmental Laws, including,  without
            limitation,  all  Environmental  Laws in  jurisdictions in which the
            Borrower owns or operates,  or has owned or operated,  a facility or
            site,  stores  Collateral,  arranges or has arranged for disposal or
            treatment  of  hazardous  substances,  solid  waste or other  waste,
            accepts or has  accepted for  transport  any  hazardous  substances,
            solid  waste or other  wastes or holds or has held any  interest  in
            real  property or  otherwise.  Except as otherwise  disclosed on the
            Addendum,  no litigation or proceeding arising under, relating to or
            in  connection  with any  Environmental  Law is  pending  or, to the
            Borrower's  knowledge,  threatened  against the  Borrower,  any real
            property  which the  Borrower  holds or has held an  interest or any
            past  or  present  operation  of the  Borrower.  To  the  Borrower's
            knowledge,  no release,  threatened release or disposal of hazardous
            waste,  solid waste or other wastes is  occurring,  or has occurred,
            on, under or to any real  property in which the  Borrower  holds any
            interest or performs any of its operations, in material violation of
            any  Environmental  Law.  As used in this  Section,  "LITIGATION  OR
            PROCEEDING"  means any demand,  claim notice,  suit, suit in equity,
            action,  administrative  action,  investigation  or inquiry  whether
            brought  by  a   governmental   authority  or  other   person,   and
            "ENVIRONMENTAL   LAWS"  means  all  provisions  of  laws,  statutes,
            ordinances, rules, regulations, permits, licenses, judgments, writs,
            injunctions,  decrees,  orders,  awards and standards promulgated by
            any governmental  authority concerning health, safety and protection
            of,  or  regulation  of  the  discharge  of  substances   into,  the
            environment.

     4.11.  INTELLECTUAL PROPERTY. The Borrower owns or has the right to use all
            patents, patent rights, and to the information, knowledge and belief
            of  the  Borrower,  Borrower  owns  or has  the  right  to  use  all
            trademarks,  trade names,  service marks,  copyrights,  intellectual
            property,  technology,  know-how  and  processes  necessary  for the
            conduct of its business as currently  conducted that are material to
            the condition  (financial or  otherwise),  business or operations of
            the Borrower.

                                       6
<PAGE>

     4.12.  YEAR 2000.  The  Borrower has reviewed the areas within its business
            and  operations  which  could  be  adversely  affected  by,  and has
            developed  or is  developing  a program to address on a timely basis
            the risk that certain computer applications used by the Borrower may
            be unable to recognize and perform properly date-sensitive functions
            involving dates prior to and after December 31, 1999 (the "YEAR 2000
            PROBLEM").  The  Year  2000  Problem  will  not  have,  and  is  not
            reasonably expected to have, a Material Adverse Effect.

     4.13.  REGULATORY MATTERS. No part of the proceeds of the Loan will be used
            for  "PURCHASING"  or  "CARRYING"  any  "MARGIN  STOCK"  within  the
            respective  meanings of each of the quoted terms under  Regulation U
            of the Board of Governors of the Federal  Reserve  System as now and
            from time to time in effect or for any purpose  which  violates  the
            provisions of the Regulations of such Board of Governors.

     4.14.  SOLVENCY.  As of the date  hereof  and  after  giving  effect to the
            transactions  contemplated by the Loan Documents,  the Borrower will
            have  sufficient  cash  flow to  enable  it to pay its debts as they
            mature.

     4.15.  DISCLOSURE. None of the Loan Documents contains any untrue statement
            of  material  fact or omits to state a material  fact  necessary  in
            order to make the statements contained in this Agreement or the Loan
            Documents  not  misleading.  There is no fact known to the  Borrower
            which materially  adversely  affects or, might materially  adversely
            affect, the business,  assets,  operations,  financial  condition or
            results of operation  of the  Borrower  and which has not  otherwise
            been fully set forth in this Agreement or in the Loan Documents.

5.   AFFIRMATIVE COVENANTS.  The Borrower agrees that from the date of execution
     of this  Agreement  until  all  Obligations  have been  fully  paid and any
     commitments of the Bank to the Borrower have been terminated,  the Borrower
     will:

     5.1.   BOOKS AND RECORDS.  Maintain  books and records in  accordance  with
            GAAP and give  representatives  of the Bank  access  thereto  at all
            reasonable  times  following   reasonable   notice  from  the  Bank,
            including  permission to examine,  copy (at the Bank's  expense) and
            make  abstracts  from any of such books and  records  and such other
            information  as the Bank may from time to time  reasonably  request,
            and the Borrower  will make  available  to the Bank for  examination
            copies of any reports,  statements or returns which the Borrower may
            make to or file with any governmental department,  bureau or agency,
            federal  or  state.   The  Bank  shall  treat  as  confidential  all
            non-public   information   contained  in  such  books  and  records;
            provided, however, that if Bank is required to disclose confidential
            information pursuant to a court order,  subpoena or similar process,
            prior to disclosure Bank shall: (i) promptly provide Borrower with a
            copy of the court order or subpoena; (ii) cooperate with Borrower at
            Borrower's  expense in obtaining a protective or similar order;  and
            (iii) in any event, disclose only such confidential information as

                                       7
<PAGE>

            Bank, with the advice of its counsel, shall deem necessary to comply
            with such court order or subpoena.

     5.2.   INTERIM FINANCIAL  STATEMENTS;  CERTIFICATE OF NO DEFAULT;  ACCOUNTS
            RECEIVABLE.

            (a) Monthly  Reporting.  Furnish  the Bank  within  twenty (20) days
            after the end of each month:

                 (i) a detailed  report on its sales and accounts  receivable in
            such  reasonable  detail  consistent with the form currently used by
            the Borrower's management;

                 (ii) an income  statement  and balance  sheet for such  period,
            each in reasonable detail, certified by an authorized officer of the
            Borrower and prepared in accordance with GAAP applied from period to
            period;

                 (iii)  a  certificate  as to  its  compliance  with  applicable
            financial  covenants for the period then ended and whether any Event
            of Default exists, and, if so, the nature thereof and the corrective
            measures the Borrower proposes to take; and

                 (iv)  a  completed  Borrowing  Base  Certificate  in  the  form
            attached to the Borrowing Base Rider.

            (b) Quarterly Reporting. Furnish the Borrower's Financial Statements
            to the Bank  within  twenty  (20)  days of the end of each  calendar
            quarter.  "FINANCIAL  STATEMENTS" means the Borrower's  consolidated
            and, if required by the Bank in its sole  discretion,  consolidating
            balance sheets,  income  statements and statements of cash flows for
            the  year  or  quarter  together  with   year-to-date   figures  and
            comparative figures for the corresponding periods of the prior year.

     5.3.   ANNUAL  FINANCIAL  STATEMENTS.   Furnish  the  Borrower's  Financial
            Statements to the Bank within ninety (90) days after the end of each
            fiscal  year.  Those  Financial   Statements  will  be  prepared  in
            accordance with GAAP and audited by an independent  certified public
            accountant  selected by the Borrower and reasonably  satisfactory to
            the Bank. Audited Financial Statements shall contain the unqualified
            opinion  of an  independent  certified  public  accountant  and  its
            examination   shall   have  been  made  in   accordance   with  GAAP
            consistently  applied from period to period.  The Borrower will also
            provide  filings made with any  regulatory  authority and such other
            information reasonably requested by the Bank from time to time.

     5.4.   PAYMENT OF TAXES AND OTHER  CHARGES.  Pay and discharge when due all
            indebtedness and all taxes,  assessments,  charges, levies and other
            liabilities imposed upon the Borrower, its income, profits, property
            or business, except those

                                       8
<PAGE>

            which  currently  are being  contested in good faith by  appropriate
            proceedings and for which the Borrower shall have set aside adequate
            reserves in accordance  with GAAP or made other  adequate  provision
            with  respect  thereto  acceptable  to the  Bank  in its  reasonable
            discretion.

     5.5.   MAINTENANCE  OF  EXISTENCE,  OPERATION  AND  ASSETS.  Do all  things
            necessary to  maintain,  renew and keep in full force and effect its
            organizational  existence  and all rights,  permits  and  franchises
            necessary  to  enable  it to  continue  its  business;  continue  in
            operation in substantially  the same manner as at present;  keep its
            properties in good operating condition and repair, ordinary wear and
            tear and  obsolescence  excepted;  and make all necessary and proper
            repairs, renewals, replacements, additions and improvements thereto.

     5.6.   INSURANCE.  Maintain with financially sound and reputable  insurers,
            insurance  with respect to its  property  and business  against such
            casualties and  contingencies,  of such types and in such amounts as
            is  customary  for  established  companies  engaged  in the  same or
            similar business and similarly situated.  In the event of a conflict
            between the provisions of this Section and the terms of any Security
            Documents  relating to  insurance,  the  provisions  in the Security
            Documents will control.

     5.7.   COMPLIANCE WITH LAWS.  Comply in all material respects with all laws
            applicable  to the  Borrower  and to the  operation  of its business
            (including  any statute,  rule or regulation  relating to employment
            practices and pension benefits or to environmental, occupational and
            health standards and controls).

     5.8.   BANK  ACCOUNTS.  Establish  and  maintain  at  the  Bank  all of the
            Borrower's primary depository accounts.

     5.9.   FINANCIAL  COVENANTS.  Comply  with all of the  financial  and other
            covenants,  if  any,  set  forth  on the  Addendum,  subject  to all
            applicable cure periods set forth herein.

     5.10.  ADDITIONAL REPORTS. Provide prompt written notice to the Bank of the
            occurrence  of any of the  following of which the  Borrower  obtains
            knowledge  (together  with a  description  of the  action  which the
            Borrower  proposes to take with respect  thereto):  (i) any Event of
            Default,  (ii)  any  material  litigation  filed by or  against  the
            Borrower,  (iii) any Reportable Event or Prohibited Transaction with
            respect to any  Employee  Benefit  Plan(s)  (as defined in ERISA) or
            (iv) any event  which  might  reasonably  be expected to result in a
            material  adverse  change  in  the  business,   assets,  operations,
            financial condition or results of operation of the Borrower.

6.   NEGATIVE COVENANTS. The Borrower covenants and agrees that from the date of
     execution of this Agreement until all Obligations  have been fully paid and
     any

                                       9
<PAGE>

     commitments of the Bank to the Borrower have been terminated,  the Borrower
     will not,  except as set forth in the  Addendum,  without the Bank's  prior
     written consent:

     6.1.   INDEBTEDNESS.  Incur, assume or permit to exist any indebtedness for
            borrowed money other than: (i)  indebtedness  under the Facility and
            any subsequent  indebtedness to the Bank; (ii) existing indebtedness
            disclosed on the Borrower's Historical Financial Statements referred
            to in Section 4.2;  (iii)  capital lease  obligations  not to exceed
            $100,000  in the  aggregate  over the term of the Loan;  (iv)  trade
            payables  incurred in the ordinary course of business;  (v) guaranty
            obligations  permitted  pursuant  to  Section  6.3  below;  or  (vi)
            indebtedness  specifically disclosed by the Borrower on the Addendum
            and any renewal or refinance of thereof  which does not increase the
            principal thereof.

     6.2.   LIENS AND  ENCUMBRANCES.  Except as provided in Section 4.6, create,
            assume or permit to exist any mortgage, pledge, encumbrance or other
            security  interest  or lien upon any assets  now owned or  hereafter
            acquired  or  enter  into  any  lease  or any  arrangement  for  the
            acquisition of property subject to any conditional  sales agreement,
            other  than (i)  leasehold  interests  related to  operating  leases
            entered  into by the  Borrower in the  ordinary  course of business,
            (ii) liens for taxes,  assessments  or charges  due and  payable and
            subject to interest or penalty, provided that the Borrower maintains
            such reserves or other  appropriate  provisions as shall be required
            by GAAP and pays all such taxes,  assessments  or charges  forthwith
            upon the  commencement  of  proceedings  to foreclose any such lien,
            (iii)  liens of  mechanics,  materialmen,  warehousemen,  repairmen,
            carriers,  or other statutory  nonconsensual liens,  provided,  that
            such  liens do not  materially  affect  the  Collateral  or,  in the
            aggregate,  materially impair the ability of the Borrower to perform
            its Obligations  hereunder or under the other Loan  Documents,  (iv)
            liens  consisting  of  zoning   restrictions,   easements  or  other
            restrictions on the use of real property,  none of which  materially
            impairs the use of such property or the value  thereof,  and none of
            which is  violated in any  material  respect by existing or proposed
            structures  or land use,  and (v)  pledges or  deposits  made in the
            ordinary   course  of  business  to  secure   payment  of  workmen's
            compensation,  or to  participate  in any  fund in  connection  with
            workmen's compensation,  unemployment insurance, old-age pensions or
            other social security programs.

     6.3.   GUARANTEES.  Guarantee,  endorse or voluntarily become  contingently
            liable  for the  obligations  of any  person,  firm or  corporation,
            except in connection  with the  endorsement and deposit of checks in
            the ordinary course of business for collection.

     6.4.   LOANS OR ADVANCES;  INVESTMENTS.  Purchase or hold  beneficially any
            stock, other securities or evidences of indebtedness of any loans or
            advances  to,  or  make  any  investment  or  acquire  any  interest
            whatsoever  in, any other person,  firm or  corporation in excess of
            $10,000 in the aggregate during the term of the Facility, except (i)
            investments   disclosed  on  the  Borrower's   Historical  Financial
            Statements

                                       10
<PAGE>

            or acceptable  to the Bank in its  reasonable  discretion,  and (ii)
            advances to employees to meet expenses incurred by such employees in
            the ordinary course of business.

     6.5.   MERGER OR TRANSFER OF ASSETS.  Merge or consolidate with or into any
            person,  firm or corporation or lease,  sell,  transfer or otherwise
            dispose of property or assets  (excluding  the sale of  inventory in
            the ordinary  course of business)  having an aggregate book value in
            excess of One Hundred Thousand Dollars  ($100,000) whether now owned
            or  hereafter  acquired  other than such  merger,  consolidation  or
            disposition approved by the Bank.

     6.6.   CHANGE IN  BUSINESS,  MANAGEMENT  OR  OWNERSHIP.  Make or permit any
            material  change in the nature of its  business  as carried on as of
            the  date  hereof,  in  the  composition  of its  current  executive
            management,  or in its equity  ownership other than (i) transfers to
            heirs  and  beneficiaries  of a  stockholder  upon  the  death  of a
            stockholder,  (ii) in connection  with an initial public offering of
            the capital  stock of the Borrower,  (iii) private  offerings of the
            equity  securities of the Borrower  approved by the Borrower's Board
            of Directors,  (iv)  issuances of shares  pursuant to the Borrower's
            employee stock option plan in effect as of the date hereof or (v) in
            connection with the repurchase of shares acquired through retirement
            plans or employee  stock option plans or pursuant to the exercise of
            contractual  rights  of  first  refusal  to  purchase  such  shares;
            provided that the Bank shall not unreasonably  withhold or delay its
            consent to a change in the Borrower's executive management which has
            been approved by the Borrower's Board of Directors.

     6.7.   DIVIDENDS.  Declare or pay any dividends on or make any distribution
            with  respect to any class of its equity or ownership  interest,  or
            purchase,  redeem,  retire or  otherwise  acquire  any of its equity
            other than (a) recessions and/or reissuance of the equity securities
            of the  Borrower  to  address  Blue Sky  matters  and (b)  purchase,
            redemption, retirement or other acquisitions of equity securities of
            the Borrower (not covered by clause (a) above) not to exceed $25,000
            in the aggregate during of the term of the Facility.

7.   EVENTS OF DEFAULT. The occurrence of any of the following will be deemed to
     be an "EVENT OF DEFAULT":

     7.1.   PAYMENT  DEFAULT.  The  Borrower  shall  fail to pay any  payment of
            principal  when  due or any  payment  of  interest  within  five (5)
            business  days  following  the date  when  due,  in  respect  of the
            Obligations.

     7.2.   MATERIAL ADVERSE CHANGE. There shall be a material adverse change in
            the business,  operations, assets, financial condition or results of
            operations of Borrower.
                                       11
<PAGE>

     7.3.   COVENANT DEFAULT.  The Borrower shall default in the performance of,
            or violate any of, the  covenants  or  agreements  contained in this
            Agreement  (other  than  with  respect  to  payment  as set forth in
            Section 7.1), which default shall not have been cured within fifteen
            (15) business days after the occurrence thereof.

     7.4.   BREACH  OF  WARRANTY.   Any  Financial  Statement,   representation,
            warranty or  certificate  made or  furnished  by the Borrower to the
            Bank in connection with this Agreement shall be false,  incorrect or
            incomplete in any material respect when made.

     7.5.   BANKRUPTCY OR INSOLVENCY. A proceeding shall have been instituted in
            a court having  jurisdiction  over the Borrower  seeking a decree or
            order for relief in respect of Borrower in an involuntary case under
            any  applicable  bankruptcy,   insolvency  reorganization  or  other
            similar law and such  involuntary  case shall remain  undismissed or
            unstayed and in effect for a period of sixty (60) consecutive  days,
            or Borrower  shall  commence a voluntary  case under any such law or
            consent to the  appointment  of a  receiver,  liquidator,  assignee,
            custodian,  trustee,  sequestrator,  conservator  (or other  similar
            official).

     7.6.   OTHER  DEFAULT.  The occurrence of an Event of Default as defined in
            the Notes or any of the Security  Documents.

Upon the  occurrence  of an Event of Default,  the Bank will have all rights and
remedies  specified in the Notes and the Security  Documents  and all rights and
remedies (which are cumulative and not exclusive) available under applicable law
or in equity.

8.   CONDITIONS. The Bank's obligation to make any Advance under the Facility is
     subject to the conditions that as of the date of the Advance:

     8.1.   FUNDING  OF  INITIAL  ADVANCE  UNDER THE  REVOLVING  CREDIT.  On the
            Closing Date:

            (a) No Event of Default. No Event of Default or event which with the
            passage of time,  provision  of notice or both would  constitute  an
            Event of Default shall have occurred and be continuing.

            (b)  Authorization  Documents.  The Borrower shall have furnished to
            the Bank  certified  copies of resolutions of the board of directors
            authorizing the execution of this Agreement, the Notes or any of the
            Security  Documents,  or  other  proof of  authorization  reasonably
            satisfactory to the Bank.

            (c) Receipt of Loan Documents.  The Borrower shall have executed and
            delivered to the Bank the Loan Documents and such other  instruments
            and documents  which the Bank may  reasonably  request in connection
            with the transactions provided for in this Agreement.

                                       12
<PAGE>

            (d)   Representations   and  Warranties.   The  representations  and
            warranties  of the Borrower to the Bank shall be true and correct in
            all respects.

            (e) Opening Balance Sheet.  The Borrower shall furnish the Bank with
            its Opening Balance Sheet. "OPENING BALANCE SHEET" means the balance
            sheet of the Borrower dated March 31, 1999.

            (f)  Opinion  of  Counsel.  Counsel  for  the  Borrower  shall  have
            delivered to the Bank, a written opinion, dated the Closing Date and
            in form and substance  reasonably  satisfactory  to the Bank and its
            counsel.

     8.2.   ADDITIONAL  ADVANCES.  At the time of making any additional Advances
            under the Revolving  Credit or the  Equipment  Line and after giving
            effect   to  any   such   proposed   extensions   of   credit:   the
            representations and warranties of the Borrower contained in the Loan
            Documents  shall  be true on and as of the date of such  funding  or
            Advance  with the same  effect as though  such  representations  and
            warranties   had  been  made  on  and  as  of  such   date   (except
            representations  and warranties  which expressly relate solely to an
            earlier date or time, which  representations and warranties shall be
            true and correct on and as of the specific  dates or times  referred
            to therein) and the Borrower  shall have performed and complied with
            all  covenants  and  conditions  hereof;  no Event of Default or any
            event  specified  in  Section 7,  which,  with the giving of notice,
            lapse of time or both, would become an Event of Default,  shall have
            occurred and be continuing or shall exist;  the advancement of funds
            under  the  Facility  shall  not   materially   contravene  any  law
            applicable  to the  Borrower  or the Bank,  as  applicable;  and the
            Borrower  shall  have  delivered  to the  Bank a duly  executed  and
            completed Advance Request.

9.   EXPENSES.  The  Borrower  agrees to pay the Bank,  upon the closing of this
     Agreement,  and  otherwise  on demand,  all  reasonable  costs and expenses
     incurred by the Bank in connection  with the (i)  preparation,  negotiation
     and  delivery  of this  Agreement  and the other  Loan  Documents,  and any
     modifications  thereto,  including reasonable fees and expenses of counsel,
     expenses for auditors, lien searches,  recording and filing fees and taxes,
     and (ii)  collection of the Loan or instituting,  maintaining,  preserving,
     enforcing and  foreclosing  the security  interest in any of the collateral
     securing the Facility,  whether through judicial  proceedings or otherwise,
     or in defending or prosecuting any actions or proceedings arising out of or
     relating to this Agreement.

10.  INCREASED COSTS. Within thirty (30) days following written demand, together
     with the  written  evidence of the  justification  therefor,  the  Borrower
     agrees to pay the Bank, all direct costs  incurred and any losses  suffered
     or payments made by the Bank as a  consequence  of making any Advance under
     the  Facility  by  reason  of  any  change  in  law  or  regulation  or its
     interpretation  imposing any  reserve,  deposit,  allocation  of capital or
     similar  requirement  (including  without  limitation,  Regulation D of the
     Board of Governors of the Federal  Reserve System) on the Bank, its holding
     company or any of their respective assets.

                                       13
<PAGE>

11. MISCELLANEOUS.

     11.1.  NOTICES. All notices,  demands,  requests,  consents,  approvals and
            other  communications  required or  permitted  hereunder  must be in
            writing and will be effective  upon receipt if delivered  personally
            to  such  party,   or  if  sent  by  facsimile   transmission   with
            confirmation  of delivery,  or by  nationally  recognized  overnight
            courier  service,  to the  address  set forth below or to such other
            address  as any  party  may give to the  other in  writing  for such
            purpose:

To the Bank:                                To the Borrower:

PNC Bank, National Association              InforMax, Inc.
1401 Eye Street, N.W.                       6110 Executive Boulevard
Suite 200                                   N. Bethesda, MD 20852
Washington, DC 20005                        Attention: Joseph Lehnen
Attention: Katherine S. Kappler             Facsimile No.: 301-984-8306
Facsimile No.: 202-393-1545

     11.2.  PRESERVATION OF RIGHTS. No delay or omission on the part of the Bank
            to exercise  any right or power  arising  hereunder  will impair any
            such right or power or be  considered  a waiver of any such right or
            power or any acquiescence  therein,  nor will the action or inaction
            of the Bank impair any right or power arising hereunder.  The Bank's
            rights and remedies  hereunder are  cumulative  and not exclusive of
            any other  rights or  remedies  which the Bank may have under  other
            agreements, at law or in equity.

     11.3.  ILLEGALITY.  In case any one or more of the provisions  contained in
            this Agreement  should be invalid,  illegal or  unenforceable in any
            respect, the validity,  legality and enforceability of the remaining
            provisions  contained  herein  shall not in any way be  affected  or
            impaired thereby.

     11.4.  CHANGES IN  WRITING.  No  modification,  amendment  or waiver of any
            provision  of this  Agreement  nor consent to any  departure  by the
            Borrower  therefrom,  will in any event be effective unless the same
            is in  writing  and  signed  by the Bank,  and then  such  waiver or
            consent shall be effective only in the specific instance and for the
            purpose for which  given.  No notice to or demand on the Borrower in
            any case will entitle the Borrower to any other or further notice or
            demand in the same, similar or other circumstance.

     11.5.  ENTIRE  AGREEMENT.  This  Agreement  (including  the  documents  and
            instruments referred to herein) constitutes the entire agreement and
            supersedes all other prior

                                       14
<PAGE>

            agreements and  understandings,  both written and oral,  between the
            parties  with   respect  to  the  subject   matter   hereof.

     11.6.  COUNTERPARTS.  This  Agreement  may  be  signed  in  any  number  of
            counterpart   copies  and  by  the   parties   hereto  on   separate
            counterparts,  but all such copies shall constitute one and the same
            instrument.

     11.7.  SUCCESSORS  AND  ASSIGNS.  This  Agreement  will be binding upon and
            inure  to the  benefit  of the  Borrower  and  the  Bank  and  their
            respective,  successors  and assigns;  provided,  however,  that the
            Borrower  may not assign this  Agreement in whole or in part without
            the prior  written  consent of the Bank and the Bank at any time may
            assign this Agreement in whole or in part, upon prior written notice
            to Borrower.

     11.8.  INTERPRETATION.  In this Agreement, unless the Bank and the Borrower
            otherwise agree in writing, the singular includes the plural and the
            plural the singular;  words  importing any gender  include the other
            genders; references to statutes are to be construed as including all
            statutory  provisions  consolidating,   amending  or  replacing  the
            statute  referred  to;  the word "or"  shall be  deemed  to  include
            "and/or",  the words "including",  "includes" and "include" shall be
            deemed to be followed by the words "without limitation";  references
            to articles,  sections (or subdivisions of sections) or exhibits are
            to  those  of  this  Agreement  unless  otherwise   indicated;   and
            references to agreements and other contractual  instruments shall be
            deemed to include all subsequent  amendments and other modifications
            to such  instruments,  but only to the extent  such  amendments  and
            other  modifications  are  not  prohibited  by  the  terms  of  this
            Agreement.  Section  headings in this  Agreement  are  included  for
            convenience  of  reference  only and shall not  constitute a part of
            this Agreement for any other purpose.  Unless otherwise specified in
            this  Agreement,  all accounting  terms shall be interpreted and all
            accounting determinations shall be made in accordance with GAAP.

     11.9.  INDEMNITY.  The Borrower  agrees to indemnify  each of the Bank, its
            directors,  officers and employees  and each legal  entity,  if any,
            which controls the Bank (the "INDEMNIFIED PARTIES") and to hold each
            Indemnified  Party  harmless  from and  against  any and all claims,
            damages,  losses,  liabilities  and  expenses  (including,   without
            limitation,  reasonable  fees of counsel  with whom any  Indemnified
            Party may  consult and all  reasonable  expenses  of  litigation  or
            preparation therefor) which any Indemnified Party may incur or which
            may be asserted against any Indemnified  Party in connection with or
            arising out of the matters  referred to in this  Agreement or in the
            other Loan  Documents by any third  person,  entity or  governmental
            authority  (including any person or entity claiming  derivatively on
            behalf of the  Borrower),  whether (a)  arising  from or incurred in
            connection with any breach of a representation, warranty or covenant
            by the Borrower,  or (b) arising out of or resulting  from any suit,
            action, claim, proceeding or governmental investigation,  pending or
            threatened,  whether based on statute, regulation or order, or tort,
            or contract or otherwise, before any court or

                                       15
<PAGE>

            governmental  authority,  which  arises  out of or  relates  to this
            Agreement,  any other Loan  Document,  or the use of the proceeds of
            the  Facility.  The  indemnity  agreement  contained in this Section
            shall  survive the  termination  of this  Agreement,  payment of any
            Advance and  assignment  of any rights  hereunder.  The Borrower may
            participate  at its  expense in the  defense  of any such  action or
            claim.

     11.10. ASSIGNMENTS  AND  PARTICIPATION.  At any time,  upon  prior  written
            notice  to the  Borrower,  the  Bank  may  sell,  assign,  transfer,
            negotiate,  grant  participation  in, or otherwise dispose of all or
            any part of the Bank's  interest  in the Loan.  Upon  prior  written
            notice  to the  Borrower,  the  Bank  may  provide  any  information
            concerning  the Borrower,  including  information  pertaining to the
            Borrower's  financial  condition,  business  operations  or  general
            creditworthiness,  to any person or entity  which may  succeed to or
            participate  in all or  any  part  of  the  Bank's  interest  in the
            Facility, provided that such person or entity agrees to maintain the
            confidentiality of such information.

     11.11. GOVERNING LAW AND JURISDICTION. This Agreement has been delivered to
            and  accepted  by the  Bank  and  will be  deemed  to be made in the
            Commonwealth of Pennsylvania. THIS AGREEMENT WILL BE INTERPRETED AND
            THE RIGHTS AND  LIABILITIES  OF THE  PARTIES  HERETO  DETERMINED  IN
            ACCORDANCE  WITH  THE  LAWS  OF THE  COMMONWEALTH  OF  PENNSYLVANIA,
            EXCLUDING   ITS  CONFLICT  OF  LAWS  RULES.   The  Borrower   hereby
            irrevocably  consents to the exclusive  jurisdiction of any state or
            federal court seated in Allegheny County, Pennsylvania, and consents
            that  all  service  of  process  be  sent by  nationally  recognized
            overnight courier service directed to the Borrower at the Borrower's
            address  set forth  herein and  service so made will be deemed to be
            completed  on the  business  day after  deposit  with such  courier;
            provided that nothing  contained in this  Agreement will prevent the
            Bank from  bringing any action,  enforcing  any award or judgment or
            exercising any rights against the Borrower individually, against any
            security or against any  property of the  Borrower  within any other
            county,  state or other foreign or domestic  jurisdiction.  The Bank
            and the  Borrower  agree that the venue  provided  above is the most
            convenient  forum for both the Bank and the  Borrower.  The Borrower
            waives  any  objection  to venue and any  objection  based on a more
            convenient forum in any action instituted under this Agreement.

     11.12. WAIVER OF JURY TRIAL.  EACH OF THE BORROWER AND THE BANK IRREVOCABLY
            WAIVES  ANY  AND ALL  RIGHT  IT MAY  HAVE TO A TRIAL  BY JURY IN ANY
            ACTION,   PROCEEDING  OR  CLAIM  OF  ANY  NATURE  RELATING  TO  THIS
            AGREEMENT,  ANY DOCUMENTS EXECUTED IN CONNECTION WITH THIS AGREEMENT
            OR  ANY  TRANSACTION  CONTEMPLATED  IN ANY OF  SUCH  DOCUMENTS.  THE
            BORROWER  AND THE BANK  ACKNOWLEDGE  THAT THE  FOREGOING  WAIVER  IS
            KNOWING AND VOLUNTARY.

                                       16
<PAGE>

The Borrower  acknowledges that it has read and understood all the provisions of
this  Agreement,  including  the waiver of jury trial,  and has been  advised by
counsel as  necessary  or  appropriate.

         WITNESS the due  execution of this Loan  Agreement as a document  under
seal, as of the date first written above.

ATTEST:                                 INFORMAX, INC.

By: /s/ Joseph E. Lehnen                By: /s/ Alex Titomirov         (SEAL)
------------------------------             -----------------------------

Print Name: Joseph E. Lehnen            Print Name: Alex Titomirov
           -------------------                     ---------------------

Title:  CFO                             Title: Chief Executive Officer
      ------------------------

                                        PNC BANK, NATIONAL
                                        ASSOCIATION

                                        By: /s/ Katharine Kappler      (SEAL)
                                           -----------------------------

                                        Print Name: Katherine Kappler
                                                   ---------------------

                                        Title: Vice President
                                              --------------------------

                                       17
<PAGE>

ADDENDUM to that certain Loan  Agreement  dated May ___, 1999 between  InforMax,
Inc.,  as the  Borrower,  and PNC  BANK,  NATIONAL  ASSOCIATION  , as the  Bank.
Capitalized terms used in this Addendum and not otherwise defined shall have the
meanings given them in such Loan Agreement.

                             I. FINANCIAL COVENANTS

1.   The  Borrower  will not permit its  Modified  Tangible Net Worth to be less
     than the  following  amounts  by the end of the fiscal  quarters  specified
     below:

     Quarter Ending                               Tangible Net Worth
     --------------                               ------------------
     June 30, 1999                                    $  424,000
     September 30, 1999                               $  503,000
     December 31, 1999                                $  622,000
     March 31, 2000                                   $  889,000
     June 30, 2000                                    $  957,000
     September 30, 2000                               $1,338,000
     December 31, 2000                                $2,144,000
     March 31, 2001                                   $2,845,000
     June 30, 2001                                    $3,602,000
     September 30, 2001                               $4,798,000
     December 31, 2001                                $5,999,000

2.   The  Borrower  shall  have a minimum  ratio of  Current  Assets to  Current
     Liabilities as follows (measured each month at month end).

                                                       Ratio of Current Assets
     Period                                            to Current Liabilities
     ------                                            ----------------------

     Closing through November 30, 1999                 1.10 to 1.00
     December 1, 1999 through April 30, 2000           1.15 to 1.00

3.   The  Borrower  shall  maintain a minimum  Cash  Balance  during each of the
     periods specified below (measured each month at month end).

     Quarter Ending                              Cash Balance
     --------------                              ------------

     June 30, 1999                                 $  108,000
     September 30, 1999                            $  129,000
     December 31, 1999                             $  139,000
     March 31, 2000                                $  172,000
     June 30, 2000                                 $  155,000
     September 30, 2000                            $  211,000
     December 31, 2000                             $  614,000
     March 31, 2001                                $1,052,000
     June 30, 2001                                 $1,513,000
     September 30, 2001                            $2,219,000
     December 31, 2001                             $2,997,000

                                      A-1
<PAGE>

DEFINITIONS:
------------

     "CASH BALANCE" means the sum of cash and marketable securities.

     "CURRENT ASSETS" means the sum of cash,  accounts receivable and marketable
     securities.

     "CURRENT  LIABILITIES"  means the sum of (a) all current  liabilities other
     than  deferred  revenue plus (b) amounts  outstanding  under the  Revolving
     Credit not classified as current liabilities.

     "MODIFIED TANGIBLE NET WORTH" means Tangible Net Worth plus 75% of deferred
     revenues (calculated in accordance with GAAP).

     "TANGIBLE  NET WORTH" means  shareholders'  equity less  intangible  assets
     (calculated in accordance with generally accepted  accounting  principles),
     plus all equity or subordinated and/or convertible debt investments created
     after the date of this Agreement.

                                      A-2

<PAGE>

                                II. DISCLOSURES
                                ---------------

4.6  TITLE TO ASSETS.
     ----------------

     See Attached Disclosure

4.7  AND 4.10 LITIGATION AND PROCEEDINGS.
              ---------------------------

     See Attached Disclosure

6.1 INDEBTEDNESS
    ------------

     None

                                      A-3

<PAGE>
                                                      EXECUTION COPY

                                 AMENDMENT NO. 1
                                       TO
                                 LOAN AGREEMENT

     THIS AMENDMENT NO. 1 TO LOAN AGREEMENT (this "AMENDMENT"),  is entered into
as of August 6,  1999,  between  INFORMAX,  INC., a Delaware  corporation  (the
"BORROWER"), and PNC BANK, NATIONAL ASSOCIATION (the "BANK").

                                   WITNESSETH:

     WHEREAS,  the Borrower and the Bank entered into a Loan Agreement  dated as
of May 6, 1999 (the "LOAN AGREEMENT")  wherein the Bank agreed to extend certain
credit facilities to the Borrower, including a $200,000 Equipment Line of Credit
(the  "EQUIPMENT  LINE"),  subject to the terms and conditions of the Agreement;
and

     WHEREAS,  the Borrower has requested that the Bank amend the Loan Agreement
to increase the maximum availability under the Equipment Line to $600,000 and to
extend the  amortization  period for each of the First Term Loan and Second Term
Loan (as each is defined in the Agreement) from twenty four to thirty months.

     NOW, THEREFORE,  in consideration of the premises herein and other good and
valuable consideration, the Borrower and the Bank, with the intent to be legally
bound hereby, agree as follows:

     1. DEFINED TERMS.  Capitalized  terms used in this Amendment shall have the
meanings  provided  in the Loan  Agreement  unless  a  different  definition  is
provided herein.

     2.  EQUIPMENT  LINE  AVAILABILITY.   The  maximum  availability  under  the
Equipment Line is hereby increased to $600,000. All Advances under the Equipment
Line  shall  continue  to be  limited  to 80% of the face  amount  of  equipment
invoices (excluding taxes, shipping and installation) submitted with any Advance
Request.

     3.  EXTENSION OF EQUIPMENT  LINE TERM.  Each of the First Term Loan and the
Second Term Loan shall provide for repayment of principal and interest in thirty
(30) equal monthly installments.

     4.  AMENDED  AND  RESTATED  LINE OF CREDIT  NOTE.  Simultaneously  with the
execution and delivery of this Amendment, the Borrower shall execute and deliver
to the Bank an Amended and Restated  Line of Credit Note (the  "AMENDED  NOTE").
Upon receipt of the

<PAGE>

Amended  Note,  the Bank shall  return to the  Borrower  the Line of Credit Note
dated May 6, 1999.

     5.  SECURITY/COLLATERAL.  All  obligations of the Borrowers,  or any one of
them,  to the Bank under the Equipment  Line,  as amended,  and the Amended Note
shall  constitute  Obligations  as  defined  in the  Loan  Agreement  and in the
Security Agreement dated as of May 6, 1999 by and between Borrower and the Bank,
and  shall  be  entitled  to the  benefits  of and be  secured  by the  Security
Documents.

     6.  FACILITY  FEE.  The  Borrower  shall pay to the Bank a facility  fee of
$3,000  (.75% of the  increased  amount of the  Equipment  Line),  payable  upon
execution of this Amendment.

     7.  REPRESENTATIONS  AND  WARRANTIES.  The Borrower  hereby  represents and
warrants to the Bank as follows:

         (a) all representations,  warranties and covenants made by the Borrower
to the Bank that are contained in the Loan Agreement,  as modified  hereby,  the
Amended Note,  and each of the other Loan  Documents are true and correct on and
as of the date  hereof  with the same  effect  as though  such  representations,
warranties  and  covenants  had been made on and as of the date  hereof  (except
representations  and warranties which expressly relate solely to an earlier date
or time, which  representations  and warranties shall be true and correct on and
as of the specific dates or times referred to therein);

         (b) to the Borrower's knowledge,  no event or condition has occurred or
exists which,  with the giving of notice or the passage of time, or both,  would
constitute an Event of Default under any of the Loan Documents;

         (c) the  Borrower has  delivered  copies of its most  recently  amended
Certificate of Incorporation and Bylaws to the Bank together with this Amendment
No. 1, and such amended  Certificate and Bylaws have not been amended,  revised,
supplemented,  restated  or changed in any way since their  respective  dates of
adoption and are still in full force and effect; and

         (d)  the  execution  and  delivery  of  this  Amendment  No.  1 and the
consummation  of the  transactions  contemplated  hereby and by the Note and any
other documents executed by the Borrower required to be delivered to the Bank in
connection  with this  Amendment No. 1 have been duly and validly  authorized by
the Borrower and all such documents  together  constitute  the legal,  valid and
binding  agreement  of  the  Borrower,   enforceable  against  the  Borrower  in
accordance with their respective terms.

     8.  REIMBURSEMENT OF EXPENSES.  The Borrower shall reimburse the Bank, upon
the execution of this  Amendment,  and otherwise on demand,  all  reasonable and
necessary  costs  and  expenses  incurred  by the  Bank in  connection  with the
preparation,  negotiation  and delivery of this  Amendment No. 1 and the Amended
Note and any modifications thereto. The obligations of

                                       2
<PAGE>

the Borrower to pay expenses  hereunder  are in addition to, and not in lieu of,
any similar obligations set forth in the Loan Agreement.

     9.  COUNTERPARTS.  This  Amendment  No.  1 may be  executed  in one or more
counterparts by any party hereto in separate counterparts, each of which when so
executed and delivered to the other party shall be deemed an original.  All such
counterparts together shall constitute one and the same instrument.

     10. WAIVERS.  This Amendment No. 1 shall not, except as expressly set forth
above,  serve to waive,  supplement  or amend  the Loan  Agreement,  which  Loan
Agreement shall remain in full force and effect as amended hereby.

                           [Signature Page to Follow]

                                       3
<PAGE>

     WITNESS the due execution of this  Amendment  No. 1 to Loan  Agreement as a
document under seal, as of the date first written above.

ATTEST:                                     INFORMAX, INC.

By:  /s/ Brigitta Lipsky                    By: /s/ Joseph E. Lehnen
   _________________________                    _________________________ (SEAL)

Print Name: Brigitta Lipsky                 Print Name: Joseph E. Lehnen
            ________________                            _________________

Title:  Controller                          Title:  Chief Financial Officer
      ______________________                       __________________________

                                            PNC BANK,
                                            NATIONAL ASSOCIATION

                                            By: /s/ Katharine Kappler
                                                _________________________ (SEAL)

                                            Print Name: Katharine Kappler
                                                        _________________

                                            Title: Vice President
                                                   ________________________

                                       4
<PAGE>
                                                                  EXECUTION COPY

                                 AMENDMENT NO. 2
                                       TO
                                 LOAN AGREEMENT

     THIS AMENDMENT NO. 2 TO LOAN AGREEMENT ("AMENDMENT NO. 2"), is entered into
as of November  30, 1999 (the  "AMENDMENT  DATE"),  between  INFORMAX,  INC.,  a
Delaware  corporation (the "BORROWER"),  and PNC BANK, NATIONAL ASSOCIATION (the
"BANK").

                                   WITNESSETH:

     WHEREAS,  the Borrower and the Bank entered into a Loan Agreement  dated as
of May 6, 1999 (the "ORIGINAL LOAN AGREEMENT") wherein the Bank agreed to extend
certain  credit  facilities  to the  Borrower,  including  an  $800,000  Secured
Revolving  Credit (the  "REVOLVING  CREDIT")  and a $200,000  Equipment  Line of
Credit  (the  "EQUIPMENT  LINE"),  subject  to the terms and  conditions  of the
Original Loan Agreement; and

     WHEREAS,  the Borrower and the Bank entered into an Amendment No. 1 to Loan
Agreement, dated as of August 6, 1999 ("AMENDMENT NO. 1"), pursuant to which the
parties  agreed to  increase  the  Equipment  Line to  $600,000  and  extend the
amortization  term for each of the  First  Term Loan and  Second  Term Loan (the
Original Loan  Agreement as amended by Amendment No. 1, is referred to herein as
the "LOAN AGREEMENT"); and

     WHEREAS,  the Borrower has  requested  that the Bank further amend the Loan
Agreement to (i) increase the maximum  availability  under each of the Revolving
Credit and the  Equipment  Line to  $1,000,000,  (ii) adjust the interest  rates
applicable  to each of the  Revolving  Credit and the  Equipment  Line and (iii)
modify certain covenants of the Borrower as described in this Second Amendment.

     NOW, THEREFORE,  in consideration of the premises herein and other good and
valuable consideration, the Borrower and the Bank, with the intent to be legally
bound hereby, agree as follows:

     1. DEFINED TERMS. Capitalized terms used in this Amendment No. 2 shall have
the meanings  provided in the Loan  Agreement  unless a different  definition is
provided herein.

     2. AVAILABILITY.

         (a) The  maximum  availability  under  the  Revolving  Credit is hereby
increased  to  $1,000,000  as of the  Amendment  Date.  All  Advances  under the
Revolving  Credit  shall  continue  to be  subject  to  the  limitations  of the
Borrowing Base Rider attached to the Loan Agreement as

<PAGE>

Exhibit A.

         (b) Equipment Line. The maximum  availability  under the Equipment Line
is hereby  increased to $1,000,000 as of the Amendment  Date. All Advances under
the  Equipment  Line shall be limited  to 100% of the face  amount of  equipment
invoices (excluding taxes, shipping and installation) submitted with any Advance
Request.

     3.  ADJUSTMENT  OF INTEREST  RATES.  Effective  as of the  Amendment  Date,
interest shall accrue at a rate of

         (a) Prime plus  1.00% per annum on all  amounts  outstanding  under the
Revolving Credit; and

         (b) Prime plus  1.25% per annum on all  amounts  outstanding  under the
Equipment Line.

The foregoing  interest rates shall apply to all amounts  outstanding  under the
Revolving  Credit and  Equipment  Line as of the Amendment  Date,  respectively,
without regard to whether Advances under such Revolving Credit or Equipment Line
were made before or after the Amendment Date.

     4. MODIFICATION OF CERTAIN COVENANTS.

         (a)  Monthly  Reporting  Requirements.   Section  5.2(a)  of  the  Loan
Agreement is hereby  amended to provide that the Borrower  shall satisfy each of
the reporting obligations under Section 5.2(a) within thirty (30) days after the
end of each month.

         (b)  Financial  Covenants.  Section  I of  the  Addendum  to  the  Loan
Agreement is hereby amended and restated in its entirety as follows:

                             I. FINANCIAL COVENANTS

1.   The  Borrower  will not permit its  Modified  Tangible Net Worth to be less
     than the  following  amounts  by the end of the fiscal  quarters  specified
     below:

     Quarter Ending                          Tangible Net Worth
     --------------                          ------------------
     June 30, 1999                           $  424,000
     September 30, 1999                      $  503,000
     December 31, 1999                       $2,794,000
     March 31, 2000                          $3,174,000
     June 30, 2000                           $3,097,000
     September 30, 2000                      $2,846,000

     Beginning with the quarter ending December 31, 2000, the Borrower shall not
     experience two consecutive quarters of Negative Net Operating Income.

                                       2
<PAGE>

2.   The  Borrower  shall  have a minimum  ratio of  Current  Assets to  Current
     Liabilities as follows (measured each month at month end).

                                                 Ratio of Current Assets
     Period                                      to Current Liabilities
     ------                                      --------------------------
     Closing through November 30, 1999           1.10 to 1.00
     December 1, 1999 through April 30, 2000     1.15 to 1.00

3.   The  Borrower  shall  maintain a minimum  Cash  Balance  during each of the
     periods specified below (measured each month at month end).

     Quarter Ending                         Cash Balance
     --------------                         ------------
     June 30, 1999                          $  108,000
     September 30, 1999                     $  129,000
     December 31, 1999                      $  750,000
     March 31, 2000                         $  750,000
     June 30, 2000                          $  750,000
     September 30, 2000                     $  750,000
     December 31, 2000                      $  750,000
     March 31, 2001                         $1,052,000
     June 30, 2001                          $1,513,000
     September 30, 2001                     $2,219,000
     December 31, 2001                      $2,997,000

DEFINITIONS:

     "CASH BALANCE" means the sum of cash and marketable securities.

     "CURRENT ASSETS" means the sum of cash,  accounts receivable and marketable
     securities.

     "CURRENT  LIABILITIES"  means the sum of (a) all current  liabilities other
     than  deferred  revenue plus (b) amounts  outstanding  under the  Revolving
     Credit not classified as current liabilities.

     "MODIFIED TANGIBLE NET WORTH" means Tangible Net Worth plus 75% of deferred
     revenues (calculated in accordance with GAAP).

     "NEGATIVE NET OPERATING  INCOME" means  earnings  before  interest,  taxes,
     depreciation and amortization  less than zero calculated in accordance with
     generally accepted accounting principles.

                                       3
<PAGE>

     "TANGIBLE  NET WORTH" means  shareholders'  equity less  intangible  assets
     (calculated in accordance with generally accepted  accounting  principles),
     plus all equity or subordinated and/or convertible debt investments created
     after the date of this Agreement.

     5. AMENDED  NOTES.  Simultaneously  with the execution and delivery of this
Amendment  No. 2, the Borrower  shall execute and deliver to the Bank an Amended
and Restated  Line of Credit Note and a Second  Amended and  Restated  Equipment
Line Note (the "AMENDED NOTES").

     6.  SECURITY/COLLATERAL.  All  obligations of the Borrowers,  or any one of
them, to the Bank under the Revolving Credit and the Equipment Line, as amended,
and the  Amended  Notes  shall  constitute  Obligations  as  defined in the Loan
Agreement and in the Security  Agreement  dated as of May 6, 1999 by and between
Borrower  and the Bank,  and shall be entitled to the benefits of and be secured
by the Security Documents.

     7. FACILITY  FEE. The Borrower  shall pay to the Bank (a) a facility fee of
$4,500 (.75% of the increased amount of the Facility),  and (b) an amendment fee
of $2,500 (.125% of the aggregate amount of the Facility,  each such fee payable
upon execution of this Amendment No. 2.

     8.  REPRESENTATIONS  AND  WARRANTIES.  The Borrower  hereby  represents and
warrants to the Bank as follows:

         (a) all representations,  warranties and covenants made by the Borrower
to the Bank that are contained in the Loan Agreement,  as modified  hereby,  the
Amended Notes,  and each of the other Loan Documents are true and correct on and
as of the date  hereof  with the same  effect  as though  such  representations,
warranties  and  covenants  had been made on and as of the date  hereof  (except
representations  and warranties which expressly relate solely to an earlier date
or time, which  representations  and warranties shall be true and correct on and
as of the specific dates or times referred to therein);

         (b) to the Borrower's knowledge,  no event or condition has occurred or
exists which,  with the giving of notice or the passage of time, or both,  would
constitute an Event of Default under any of the Loan Documents;

         (c) the  Borrower has  delivered  copies of its most  recently  amended
Certificate of Incorporation and Bylaws to the Bank together with this Amendment
No. 2, and such amended  Certificate and Bylaws have not been amended,  revised,
supplemented,  restated  or changed in any way since their  respective  dates of
adoption and are still in full force and effect; and

                                       4
<PAGE>

         (d)  the  execution  and  delivery  of  this  Amendment  No.  2 and the
consummation of the  transactions  contemplated  hereby and by the Amended Notes
and any other documents executed by the Borrower required to be delivered to the
Bank in  connection  with  this  Amendment  No. 2 have  been  duly  and  validly
authorized by the Borrower and all such documents together constitute the legal,
valid and binding agreement of the Borrower, enforceable against the Borrower in
accordance with their respective terms.

     9.  REIMBURSEMENT OF EXPENSES.  The Borrower shall reimburse the Bank, upon
the execution of this  Amendment,  and otherwise on demand,  all  reasonable and
necessary  costs  and  expenses  incurred  by the  Bank in  connection  with the
preparation,  negotiation  and delivery of this  Amendment No. 2 and the Amended
Notes and any  modifications  thereto.  The  obligations  of the Borrower to pay
expenses  hereunder  are in  addition  to,  and  not in  lieu  of,  any  similar
obligations set forth in the Loan Agreement.

     10. NOTICES. The addresses for notices provided in Section 11.1 of the Loan
Agreement are hereby amended and restated as follows:

To the Bank:                                To the Borrower:

PNC Bank, National Association              InforMax, Inc.
Venture Bank @ PNC                          6010 Executive Boulevard
11600 Sunrise Valley Drive                  N. Bethesda, MD  20852
Reston, VA  20191                           Attention:  Joseph Lehnen
Attention:  Katharine S. Kappler            Facsimile No.:  240-223-0025
Facsimile No.:  703-391-9734

     11.  COUNTERPARTS.  This  Amendment  No. 2 may be  executed  in one or more
counterparts by any party hereto in separate counterparts, each of which when so
executed and delivered to the other party shall be deemed an original.  All such
counterparts together shall constitute one and the same instrument.

     12. WAIVERS.  This Amendment No. 2 shall not, except as expressly set forth
above,  serve to waive,  supplement  or amend  the Loan  Agreement,  which  Loan
Agreement shall remain in full force and effect as amended hereby.

                           [Signature Page to Follow]

                                       5
<PAGE>

     WITNESS the due execution of this  Amendment  No. 2 to Loan  Agreement as a
document under seal, as of the date first written above.

ATTEST:                                     INFORMAX, INC.

By: /s/ Joseph E. Lehnen                     By: /s/ Alex Titomirov
    ________________________                   _________________________ (SEAL)

Print Name: Joseph E. Lehnen                Print Name: Alex Titomirov
            ________________                            _________________

Title: Chief Financial Officer              Title: President/CEO
      ________________________                     ______________

                                            PNC BANK,
                                            NATIONAL ASSOCIATION

                                            By: /s/ Katherine Kappler
                                              _________________________ (SEAL)

                                            Print Name: Katherine Kappler
                                                        _________________

                                            Title: Vice President
                                                  __________________________

                                       6
<PAGE>

                                                                  EXECUTION COPY

                                 AMENDMENT NO. 3
                                       TO
                                 LOAN AGREEMENT

     THIS AMENDMENT NO. 3 TO LOAN AGREEMENT ("AMENDMENT NO. 3"), is entered into
as of February 7 2000 (the "AMENDMENT DATE"), between INFORMAX, INC., a Delaware
corporation (the "BORROWER"), and PNC BANK, NATIONAL ASSOCIATION (the "BANK").

                                   WITNESSETH:

         WHEREAS,  the Borrower and the Bank entered into a Loan Agreement dated
as of May 6, 1999 (the  "ORIGINAL  LOAN  AGREEMENT")  wherein the Bank agreed to
extend certain credit facilities to the Borrower,  including an $800,000 Secured
Revolving  Credit (the  "REVOLVING  CREDIT")  and a $200,000  Equipment  Line of
Credit  (the  "EQUIPMENT  LINE"),  subject  to the terms and  conditions  of the
Original Loan Agreement; and

     WHEREAS,  the Borrower and the Bank entered into an Amendment No. 1 to Loan
Agreement, dated as of August 6, 1999 ("AMENDMENT NO. 1"), pursuant to which the
parties  agreed to  increase  the  Equipment  Line to  $600,000  and  extend the
amortization term for each of the First Term Loan and Second Term Loan; and

     WHEREAS,  the Borrower and the Bank entered into an Amendment No. 2 to Loan
Agreement,  dated as of November 30, 1999 ("AMENDMENT NO. 2"), pursuant to which
the parties  agreed to (i) increase the maximum  availability  under each of the
Revolving Credit and the Equipment Line to $1,000,000,  (ii) adjust the interest
rates  applicable  to each of the Revolving  Credit and the  Equipment  Line and
(iii) modify  certain  covenants of the Borrower as described in Amendment No. 2
(the Original Loan  Agreement as amended by Amendment No. 1 and Amendment No. 2,
is referred to herein as the "LOAN AGREEMENT"); and

     WHEREAS,  the Borrower has  requested  that the Bank further amend the Loan
Agreement to (i) increase the maximum  availability  under each of the Revolving
Credit and the Equipment Line to $3,000,000, (ii) extend the expiration date for
the  Revolving  Credit,  and (iii) modify  certain  covenants of the Borrower as
described in this Amendment No. 3.

     NOW, THEREFORE,  in consideration of the premises herein and other good and
valuable consideration, the Borrower and the Bank, with the intent to be legally
bound hereby, agree as follows:

<PAGE>

     1. DEFINED TERMS. Capitalized terms used in this Amendment No. 3 shall have
the meanings  provided in the Loan  Agreement  unless a different  definition is
provided herein.

     2. EXPIRATION  DATE. The "REVOLVING  CREDIT  EXPIRATION  DATE" shall be the
date three hundred sixty four (364) days after the Amendment Date.

     3. AVAILABILITY.

         (a)  Revolving  Credit.  The maximum  availability  under the Revolving
Credit is hereby  increased to $3,000,000 as of the Amendment Date. All Advances
under the Revolving  Credit shall  continue to be subject to the  limitations of
the Borrowing Base Rider attached to the Loan Agreement as Exhibit A.

         (b) Equipment Line. The maximum  availability  under the Equipment Line
is hereby  increased to $3,000,000 as of the Amendment  Date. All Advances under
the  Equipment  Line shall be limited  to 100% of the face  amount of  equipment
invoices (excluding taxes, shipping and installation) submitted with any Advance
Request.

     4.  ADJUSTMENT  OF INTEREST  RATES.  Effective  as of the  Amendment  Date,
interest shall accrue at a rate of

         (a) Prime plus  1.00% per annum on all  amounts  outstanding  under the
Revolving Credit; and

         (b) Prime plus  1.25% per annum on all  amounts  outstanding  under the
Equipment Line.

The foregoing  interest rates shall apply to all amounts  outstanding  under the
Revolving  Credit and  Equipment  Line as of the Amendment  Date,  respectively,
without regard to whether Advances under such Revolving Credit or Equipment Line
were made before or after the Amendment Date.

     5. MODIFICATION OF CERTAIN COVENANTS. Section I of the Addendum to the Loan
Agreement is hereby amended and restated in its entirety as follows:

                             I. FINANCIAL COVENANTS

1.   The  Borrower  will not permit its  Modified  Tangible Net Worth to be less
     than the  following  amounts  by the end of the fiscal  quarters  specified
     below:

     Quarter Ending                         Tangible Net Worth
     --------------                         ------------------
     March 31, 2000                         $2,900,000
     June 30, 2000                          $2,900,000
     September 30, 2000                     $2,300,000
     December 31, 2000                      $3,100,000

<PAGE>

     Beginning with the quarter ending December 31, 2000, the Borrower shall not
     experience two consecutive quarters of Negative Net Operating Income.

2.   The Borrower  shall at all times during the term of this  Agreement  have a
     minimum  ratio of  Current  Assets to Current  Liabilities  of 1.50 to 1.00
     (measured each month at month end).

3.   The Borrower shall at all times during the term of this Agreement  maintain
     a minimum Cash Balance of $750,000 (measured each month at month end).

4.   The Borrower shall at all times during the term of this Agreement  maintain
     a maximum  ratio of Modified  Total  Liabilities  to Modified  Tangible Net
     Worth of 1.50 to 1.00 (measured each month at month end).

DEFINITIONS:

     "CASH BALANCE" means the sum of cash and marketable securities.

     "CURRENT ASSETS" means the sum of cash,  accounts receivable and marketable
     securities.

     "CURRENT  LIABILITIES"  means the sum of (a) all current  liabilities other
     than  deferred  revenue plus (b) amounts  outstanding  under the  Revolving
     Credit not classified as current liabilities.

     "MODIFIED TOTAL  LIABILITIES"  means all current and long term liabilities,
     less deferred revenues.

     "MODIFIED TANGIBLE NET WORTH" means Tangible Net Worth plus 75% of deferred
     revenues (calculated in accordance with GAAP).

     "NEGATIVE NET OPERATING  INCOME" means  earnings  before  interest,  taxes,
     depreciation and amortization  less than zero calculated in accordance with
     generally accepted accounting principles.

     "TANGIBLE  NET WORTH" means  shareholders'  equity less  intangible  assets
     (calculated in accordance with generally accepted  accounting  principles),
     plus all equity or subordinated and/or convertible debt investments created
     after the date of this Agreement.

     6. AMENDED  NOTES.  Simultaneously  with the execution and delivery of this
Amendment  No. 3, the  Borrower  shall  execute and deliver to the Bank a Second
Amended  and  Restated  Line of Credit  Note and a Third  Amended  and  Restated
Equipment Line of Credit Note (the "AMENDED NOTES").

<PAGE>

     7.  SECURITY/COLLATERAL.  All  obligations of the Borrowers,  or any one of
them, to the Bank under the Revolving Credit and the Equipment Line, as amended,
and the  Amended  Notes  shall  constitute  Obligations  as  defined in the Loan
Agreement and in the Security  Agreement  dated as of May 6, 1999 by and between
Borrower  and the Bank,  and shall be entitled to the benefits of and be secured
by the Security Documents.

     8. FACILITY  FEE. The Borrower  shall pay to the Bank (a) a facility fee of
$20,000 (.50% of the increased amount of the Facility), and (b) an amendment fee
of $7,500 (.125% of the aggregate amount of the Facility), each such fee payable
upon execution of this Amendment No. 3.

     9.  REPRESENTATIONS  AND  WARRANTIES.  The Borrower  hereby  represents and
warrants to the Bank as follows:

         (a) all representations,  warranties and covenants made by the Borrower
to the Bank that are contained in the Loan Agreement,  as modified  hereby,  the
Amended Notes,  and each of the other Loan Documents are true and correct on and
as of the date  hereof  with the same  effect  as though  such  representations,
warranties  and  covenants  had been made on and as of the date  hereof  (except
representations  and warranties which expressly relate solely to an earlier date
or time, which  representations  and warranties shall be true and correct on and
as of the specific dates or times referred to therein);

         (b) to the Borrower's knowledge,  no event or condition has occurred or
exists which,  with the giving of notice or the passage of time, or both,  would
constitute an Event of Default under any of the Loan Documents;

         (c) the  Borrower has  delivered  copies of its most  recently  amended
Certificate of Incorporation and Bylaws to the Bank together with this Amendment
No. 3, and such amended  Certificate and Bylaws have not been amended,  revised,
supplemented,  restated  or changed in any way since their  respective  dates of
adoption and are still in full force and effect; and

         (d)  the  execution  and  delivery  of  this  Amendment  No.  3 and the
consummation of the  transactions  contemplated  hereby and by the Amended Notes
and any other documents executed by the Borrower required to be delivered to the
Bank in  connection  with  this  Amendment  No. 3 have  been  duly  and  validly
authorized by the Borrower and all such documents together constitute the legal,
valid and binding agreement of the Borrower, enforceable against the Borrower in
accordance with their respective terms.

     10. REIMBURSEMENT OF EXPENSES.  The Borrower shall reimburse the Bank, upon
the execution of this  Amendment,  and otherwise on demand,  all  reasonable and
necessary  costs  and  expenses  incurred  by the  Bank in  connection  with the
preparation,  negotiation  and delivery of this  Amendment No. 3 and the Amended
Notes and any  modifications  thereto.  The  obligations

<PAGE>

of the  Borrower to pay expenses  hereunder  are in addition to, and not in lieu
of, any similar obligations set forth in the Loan Agreement.

     11. NOTICES. The addresses for notices provided in Section 11.1 of the Loan
Agreement are hereby amended and restated as follows:

To the Bank:                                To the Borrower:

PNC Bank, National Association              InforMax, Inc.
Venture Bank @ PNC                          6010 Executive Boulevard
11600 Sunrise Valley Drive                  N. Bethesda, MD  20852
Reston, VA  20191                           Attention:  Joseph Lehnen
Attention:  Katharine S. Kappler            Facsimile No.:  240-223-0025
Facsimile No.:  703-391-9734

     12.  COUNTERPARTS.  This  Amendment  No. 3 may be  executed  in one or more
counterparts by any party hereto in separate counterparts, each of which when so
executed and delivered to the other party shall be deemed an original.  All such
counterparts together shall constitute one and the same instrument.

     13. WAIVERS.  This Amendment No. 3 shall not, except as expressly set forth
above,  serve to waive,  supplement  or amend  the Loan  Agreement,  which  Loan
Agreement shall remain in full force and effect as amended hereby.

                           [Signature Page to Follow]

<PAGE>

     WITNESS the due execution of this  Amendment  No. 3 to Loan  Agreement as a
document under seal, as of the date first written above.

ATTEST:                                     INFORMAX, INC.

By: /s/ Joseph E. Lehnen                     By: /s/ Alex Titomirov
    ________________________                   _________________________ (SEAL)

Print Name: Joseph E. Lehnen                Print Name: Alex Titomirov
            ________________                            _________________

Title: CEO                                  Title: CEO
      ________________________                     ______________

                                            PNC BANK,
                                            NATIONAL ASSOCIATION

                                            By: /s/ Katherine Kappler
                                              _________________________ (SEAL)

                                            Print Name: Katherine Kappler
                                                        _________________

                                            Title: Vice President
                                                  __________________________

<PAGE>

                                                              K&L DRAFT: 4/13/00

                                 AMENDMENT NO. 4
                                       TO
                                 LOAN AGREEMENT

     THIS AMENDMENT NO. 4 TO LOAN AGREEMENT ("AMENDMENT NO. 4"), effective as of
February 29, 2000 (the "AMENDMENT  DATE"),  between  INFORMAX,  INC., a Delaware
corporation (the "BORROWER"), and PNC BANK, NATIONAL ASSOCIATION (the "BANK").

                                   WITNESSETH:

     WHEREAS,  the Borrower and the Bank entered into a Loan Agreement  dated as
of May 6, 1999 (the "ORIGINAL LOAN AGREEMENT") wherein the Bank agreed to extend
certain  credit  facilities  to the  Borrower,  including  an  $800,000  Secured
Revolving  Credit (the  "REVOLVING  CREDIT")  and a $200,000  Equipment  Line of
Credit  (the  "EQUIPMENT  LINE"),  subject  to the terms and  conditions  of the
Original Loan Agreement; and

     WHEREAS,  the Borrower and the Bank entered into an Amendment No. 1 to Loan
Agreement, dated as of August 6, 1999 ("AMENDMENT NO. 1"), pursuant to which the
parties  agreed to  increase  the  Equipment  Line to  $600,000  and  extend the
amortization term for each of the First Term Loan and Second Term Loan; and

     WHEREAS,  the Borrower and the Bank entered into an Amendment No. 2 to Loan
Agreement,  dated as of November 30, 1999 ("AMENDMENT NO. 2"), pursuant to which
the parties  agreed to (i) increase the maximum  availability  under each of the
Revolving Credit and the Equipment Line to $1,000,000,  (ii) adjust the interest
rates  applicable  to each of the Revolving  Credit and the  Equipment  Line and
(iii) modify certain  covenants of the Borrower as described in Amendment No. 2;
and

     WHEREAS,  the Borrower and the Bank entered into an Amendment No. 3 to Loan
Agreement,  dated as of February __, 2000  ("AMENDMENT NO. 3") pursuant to which
the parties  agreed to (i) increase the maximum  availability  under each of the
Revolving  Credit  and  the  Equipment  Line  to  $3,000,000,  (ii)  extend  the
expiration  date for the Revolving  Credit,  and (iii) modify certain  financial
covenants of the Borrower (the Original Loan Agreement,  as amended by Amendment
No. 1,  Amendment No. 2 and Amendment No. 3, is referred to herein as the ("LOAN
AGREEMENT"); and

     WHEREAS,  the Borrower has  requested  that the Bank further amend the Loan
Agreement to modify the definition of "Cash Balance" as such term is used in one
or more of the Borrower's financial covenants,  set forth in the Addendum to the
Loan Agreement.

<PAGE>

         NOW, THEREFORE,  in consideration of the premises herein and other good
and valuable  consideration,  the  Borrower and the Bank,  with the intent to be
legally bound hereby, agree as follows:

     1. DEFINED TERMS. Capitalized terms used in this Amendment No. 4 shall have
the meanings  provided in the Loan  Agreement  unless a different  definition is
provided herein.

     2. MODIFICATION OF CERTAIN COVENANTS.  The definition of "Cash Balance" set
forth in the Addendum to the Loan  Agreement  is hereby  amended and restated in
its entirety as follows:

         "CASH BALANCE" means the sum of cash and marketable  securities plus an
         amount equal to the Borrower's excess  availability under the Revolving
         Credit.

     3.  REPRESENTATIONS  AND  WARRANTIES.  The Borrower  hereby  represents and
warrants to the Bank as follows:

         (a) all representations,  warranties and covenants made by the Borrower
to the Bank that are contained in the Loan Agreement,  as modified  hereby,  and
each of the other  Loan  Documents  are true and  correct  on and as of the date
hereof  with the same  effect as though  such  representations,  warranties  and
covenants had been made on and as of the date hereof (except representations and
warranties  which  expressly  relate  solely to an earlier  date or time,  which
representations  and  warranties  shall  be true  and  correct  on and as of the
specific dates or times referred to therein);

         (b) to the Borrower's knowledge,  no event or condition has occurred or
exists which,  with the giving of notice or the passage of time, or both,  would
constitute an Event of Default under any of the Loan Documents;

         (c) the  copies of the  Borrower's  Certificate  of  Incorporation  and
Bylaws  most  recently  delivered  to the Bank have not been  amended,  revised,
supplemented,  restated  or changed in any way since their  respective  dates of
adoption and are still in full force and effect; and

         (d)  the  execution  and  delivery  of  this  Amendment  No.  4 and the
consummation of the  transactions  contemplated  hereby and by the Amended Notes
and any other documents executed by the Borrower required to be delivered to the
Bank in  connection  with  this  Amendment  No. 4 have  been  duly  and  validly
authorized by the Borrower and all such documents together constitute the legal,
valid and binding agreement of the Borrower, enforceable against the Borrower in
accordance with their respective terms.

     4.  REIMBURSEMENT OF EXPENSES.  The Borrower shall reimburse the Bank, upon
the execution of this  Amendment No. 4, and otherwise on demand,  all reasonable
and necessary  costs and expenses  incurred by the Bank in  connection  with the
preparation,   negotiation  and  delivery  of  this  Amendment  No.  4  and  any
modifications hereto. The obligations of the

<PAGE>

Borrower to pay expenses  hereunder  are in addition to, and not in lieu of, any
similar obligations set forth in the Loan Agreement.

     5.  COUNTERPARTS.  This  Amendment  No.  4 may be  executed  in one or more
counterparts by any party hereto in separate counterparts, each of which when so
executed and delivered to the other party shall be deemed an original.  All such
counterparts together shall constitute one and the same instrument.

     6.  LIMITATION  OF  WAIVERS.  This  Amendment  No. 4 shall  not,  except as
expressly  set  forth  above,  serve to  waive,  supplement  or  amend  the Loan
Agreement, which Loan Agreement shall remain in full force and effect as amended
hereby.

                           [Signature Page to Follow]

<PAGE>

     WITNESS the due execution of this  Amendment  No. 4 to Loan  Agreement as a
document under seal, as of the date first written above.

ATTEST:                                     INFORMAX, INC.

ATTEST:                                     INFORMAX, INC.

By: /s/ Cecile A. Thorp                     By: /s/ Alex Titomirov
    ________________________                   _________________________ (SEAL)

Print Name: Cecile A. Thorp                Print Name: Alex Titomirov
            ________________                            _________________

Title: Benefits Administrator              Title: President/CEO
      ________________________                     ______________

Original documents                          PNC BANK,
appeared and signed before                  NATIONAL ASSOCIATION
me this 17th day of
April, 2000                                 By: /s/ Katharine Kappler
                                                _________________________ (SEAL)

                                            Print Name: Katharine Kappler
                                                        _________________
Notary Public
State of Maryland
Commission expires:
February 3, 2004                            Title: Managing Director
                                                __________________________

<PAGE>

                                 AMENDMENT NO. 5

                                       TO

                                 LOAN AGREEMENT

     THIS  AMENDMENT NO. 5 TO LOAN  AGREEMENT (" AMENDMENT NO. 5"),  dated as of
June 19,  2000 (the  "AMENDMENT  DATE"),  between  INFORMAX,  INC.,  a  Delaware
corporation (the "BORROWER"), and PNC BANK, NATIONAL ASSOCIATION (the "BANK").

                                  WITNESSETH:

     WHEREAS,  the Borrower and the Bank entered into a Loan Agreement  dated as
of May 6, 1999 (the "ORIGINAL LOAN AGREEMENT") wherein the Bank agreed to extend
certain  credit  facilities  to the  Borrower,  including  an  $800,000  Secured
Revolving  Credit (the  "REVOLVING  CREDIT")  and a $200,000  Equipment  Line of
Credit  (the  "EQUIPMENT  LINE"),  subject  to the terms and  conditions  of the
Original Loan Agreement; and

     WHEREAS,  the Borrower and the Bank entered into an Amendment No. 1 to Loan
Agreement, dated as of August 6, 1999 ("AMENDMENT NO. 1"), pursuant to which the
parties  agreed to  increase  the  Equipment  Line to  $600,000  and  extend the
amortization term for each of the First Term Loan and Second Term Loan; and

     WHEREAS,  the Borrower and the Bank entered into an Amendment No. 2 to Loan
Agreement,  dated as of November 30, 1999 ("AMENDMENT NO. 2"), pursuant to which
the parties  agreed to (i) increase the maximum  availability  under each of the
Revolving Credit and the Equipment Line to $1,000,000,  (ii) adjust the interest
rates  applicable  to each of the Revolving  Credit and the  Equipment  Line and
(iii) modify certain  covenants of the Borrower as described in Amendment No. 2;
and

     WHEREAS,  the Borrower and the Bank entered into an Amendment No. 3 to Loan
Agreement,  dated as of February 7, 2000  ("AMENDMENT  NO. 3") pursuant to which
the parties  agreed to (i) increase the maximum  availability  under each of the
Revolving  Credit  and  the  Equipment  Line  to  $3,000,000,  (ii)  extend  the
expiration  date for the Revolving  Credit,  and (iii) modify certain  financial
covenants of the Borrower; and

     WHEREAS,  the Borrower and the Bank entered into an Amendment No. 4 to Loan
Agreement,  effective  as of February 29, 2000  ("AMENDMENT  NO. 4") pursuant to
which the parties agreed to modify the definition of "Cash Balance" set forth in
the Addendum to the Original Loan  Agreement  (the Original Loan  Agreement,  as
amended by Amendment No. 1, Amendment No. 2, Amendment No. 3 and Amendment No. 4
is referred to herein as the "LOAN AGREEMENT"); and

<PAGE>

     WHEREAS,  the Borrower has  requested  that the Bank further amend the Loan
Agreement  to (i)  provide  a  %3,000,000  bridge  loan to fund  the  Borrower's
operating expenses; (ii) modify certain financial covenants of the Borrower.

     NOW, THEREFORE,  in consideration of the premises herein and other good and
valuable consideration, the Borrower and the Bank, with the intent to be legally
bound hereby, agree as follows:

     1. DEFINED TERMS. Capitalized terms used in this Amendment No. 5 shall have
the meanings  provided in the Loan  Agreement  unless a different  definition is
provided herein.

     2. FACILITY.  The term "Facility" is hereby amended to include a $3,000,000
Bridge Loan ("BRIDGE LOAN").  The proceeds of the Bridge Loan shall be used only
for funding operating expenses.

     3. BRIDGE LOAN EXPIRATION DATE. All outstanding borrowings under the Bridge
Loan,  together with all fees and expenses  related thereto and interest accrued
thereon,  shall  become due and  payable in their  entirety  upon the earlier to
occur of (i)  December  19,  2000 and (ii)  closing  date of an  initial  public
offering of any capital  stock of the Borrower or any other equity event whereby
any holder or holders  of the  Borrower's  capital  stock  infuse(s)  additional
assets,  whereby  cash or  non-cash,  to Borrower  either as a  contribution  of
capital,  loan or otherwise of at least  $3,000,000 (the "BRIDGE LOAN EXPIRATION
DATE").

     4. MANDATORY PREPAYMENTS.  The Borrower shall made Mandatory Prepayments as
follows:

        (i)    From Effective Date through  Expiration  Date. From the effective
               date of this  Amendment No. 5 through the Bridge Loan  Expiration
               Date, all contributions to the equity of the Borrower,  including
               but not limited to funds raised through venture  capital rounds,
               sales of equity to strategic  investors,  private placements,  or
               other sales of equity,  will give rise to an obligation to make a
               prepayment  (a  "MANDATORY  PREPAYMENT")  to the Bank on the same
               Business  Day in the  amount of the equity  contribution,  net of
               reasonable  expenses,  up to the maximum  aggregate amount of the
               principal  amount of the Bridge Loan outstanding at such date and
               accrued interest thereon; provided, however, contributions to the
               Borrower's  equity in an  aggregate  amount of up to Four Million
               Dollars ($4,000,000) from Emerging Tech Ventures,  Cogene Biotech
               Ventures  and   Partech   International,   or  their   respective
               affiliates, will not cause a Mandatory Prepayment.

        (ii)   Application of Prepayments. Mandatory Prepayments will be applied
               first to accrued interest and then to principal.  Amounts prepaid
               may not be reborrowed.

                                       -2-

<PAGE>

     5. INTEREST  RATE.  The interest rate for the Bridge Loan is the Prime Rate
(as  defined in the Loan  Agreement)  plus 2.50% per  annum.  Interest  shall be
calculated  on the basis of a year of 360 days and shall be  payable  monthly in
arrears.

     6. FACILITY FEE. The Borrower  shall pay the Bank a facility fee of $7,500,
payable upon the execution of this Amendment No. 5.

     7.  AVAILABILITY.  Subject  to the  other  terms  and  conditions  of  this
Amendment  No. 5 and provided  that the Borrower is in  compliance  with all the
other terms and  conditions of the Loan  Agreement,  the Borrower may draw up to
$1,500,000  within 10 days of the  execution of this  Amendment  No. 5 and up to
$500,000 (in increments of $250,000) each month for the three months  thereafter
up to a maximum aggregate amount of $3,000,000.

     8. BRIDGE LOAN NOTE.  The obligation of the Borrower to repay the aggregate
unpaid  principal  amount of the Bridge Loan,  together with  interest  thereon,
shall be  evidenced  by a promissory  note of the  Borrower  attached  hereto as
Exhibit A (the "BRIDGE NOTE" and together with the Revolving Credit Note and the
Term Note, as amended, the "NOTES") payable to the order of the Bank.

     9. MODIFICATION OF CERTAIN COVENANTS. Section I of the Addendum to the Loan
Agreement is hereby amended and restated in its entirety as follows:

                            "I. FINANCIAL COVENANTS

1. The Borrower will not permit its Modified  Tangible Net Worth to be less than
the following amounts by the end of the fiscal quarters specified below:

            ------------------------------------------------
            Quarter Ending             Modified Tangible Net
            --------------             ---------------------
                                       Worth
                                       -----
            ------------------------------------------------
            June 30, 2000              $1,078,000
            ------------------------------------------------
            September 30, 2000            357,000
            ------------------------------------------------
            December 31, 2000           3,006,000
            ------------------------------------------------

   Beginning with the quarter ending December 31, 2000, the Borrower  shall  not
not experience two consecutive quarters of Negative Net Operating Income.

2. The  Borrower  shall at all times  during the term of this  Agreement  have a
minimum ratio of Current  Assets to Current  liabilities  of 1.50:1.0  (measured
each month at month end);  provided,  however,  that the  Borrower  shall not be
required to satisfy this  financial  covenant  until the Bridge Loan  Expiration
Date.

3. The Borrower shall at all times during the term of this Agreement  maintain a
minimum Cash Balance of $750,000 (measured each month at month end).

                                      -3-

<PAGE>

4. The Borrower shall at all times during the term of this Agreement  maintain a
maximum ratio of Modified Total  Liabilities  to Modified  Tangible Net Worth of
1.50:1.0  (measured  each  month  at month  end);  provided,  however,  that the
Borrower  shall not be required to satisfy  this  financial  covenant  until the
Bridge Loan Expiration Date.

5. While  amounts due under the Bridge Loan are  outstanding,  Borrower will not
permit its Pre-Tax Loss  (calculated  in accordance  with GAAP)  determined on a
cumulative  basis, to be more than the following  amounts at the times specified
below:

            ------------------------------------------------
             Quarter Ending            Maximum Pre-Tax Loss
            ------------------------------------------------
             June 30, 2000             ($1,581,000)
            ------------------------------------------------
             September 30, 2000         (3,158,000)
            ------------------------------------------------
             December 31, 2000          (1,861,000)
            ------------------------------------------------
             March 31, 2001               (490,000)
            ------------------------------------------------

6. While  amounts due under the Bridge Loan are  outstanding,  Borrower will not
permit its Revenue,  determined on a cumulative basis from January 1, 2000 until
December 31, 2000 and on a rolling  four-quarter  basis  thereafter,  to be less
than the following amounts at the times specified below:

            ------------------------------------------------
             Quarter Ending            Minimum Revenue
            ------------------------------------------------
             June 30, 2000             $6,599,000
            ------------------------------------------------
             September 30, 2000         9,626,000
            ------------------------------------------------
             December 31, 2000         14,951,000
            ------------------------------------------------
             March 31, 2001            18,045,000
            ------------------------------------------------

DEFINITIONS:

     "CASH  BALANCE"  means the sum of cash and  marketable  securities  plus an
amount equal to the Borrower's excess availability under the Revolving Credit.

     "CURRENT ASSETS" means the sum of cash,  accounts receivable and marketable
securities.

     "CURRENT  LIABILITIES"  means the sum of (a) all current  liabilities other
than deferred  revenue plus (b) amounts  outstanding  under the Revolving Credit
not classified as current liabilities.

     "MODIFIED TOTAL  LIABILITIES"  means all current and long term liabilities,
less deferred revenues.

     "MODIFIED TANGIBLE NET WORTH" means Tangible Net Worth plus 75% of deferred
revenues (calculated in accordance with GAAP).

                                      -4-

<PAGE>

     "NEGATIVE NET OPERATING  INCOME" means  earnings  before  interest,  taxes,
depreciation and amortization less than zero calculated in accordance with GAAP.

     "PRE-TAX LOSS" for any period (cumulative or rolling) means earnings before
calculation  and  payment  of  taxes as  reported  on the  balance  sheet of the
Borrower on the last day of the reporting period.

     "REVENUE" means the sum of cumulative and deferred revenues.

     "TANGIBLE  NET WORTH" means  shareholders'  equity less  intangible  assets
(calculated in accordance  with GAAP),  plus all equity or  subordinated  and/or
convertible debt investments created after the date of this Agreement."

     10. SECURITY/COLLATERAL.  All obligations of the Borrower to the Bank under
the Revolving  Credit,  Equipment  Line,  Bridge Loan and the Notes, as amended,
constitute  Obligations  as defined in the Loan  Agreement  and in the  Security
Agreement dated as of May 6, 1999 by and between Borrower and Bank,  entitled to
the benefits of and secured by the Security Documents.

     11.  WARRANTS.  In  partial  consideration  for  the  Bridge  Loan  and the
financial accommodations extended to the Borrower under and pursuant to the Loan
Agreement  provided  herein,  the  Borrower  will,  upon the  execution  of this
Amendment  No. 5, grant to Bank  warrants  to  purchase  the  non-voting  common
capital stock of Borrower (the  "WARRANTS")  (i) in the initial  amount of 9,000
shares; and (ii) an additional 6,000 shares if amounts due under the Bridge Loan
are unpaid on September 19, 2000, in accordance with and subject to the terms of
the  Warrant  Purchase  Agreement  attached  hereto as Exhibit B (the   "WARRANT
AGREEMENT")  and at an exercise  price set forth in the Warrant  Agreement  (the
Loan Agreement,  this Amendment No. 5, the Notes, the Security Documents and the
Warrant Agreement are collectively referred to as the "LOAN DOCUMENTS").

     12.  REPRESENTATIONS  AND WARRANTIES.  The Borrower  hereby  represents and
warrants to the Bank as follows:

          (a) all representations, warranties and covenants made by the Borrower
to the Bank that are contained in the Loan Agreement,  as modified  hereby,  and
each of the other  Loan  Documents  are true and  correct  on and as of the date
hereof  with the same  effect as though  such  representations,  warranties  and
covenants had been made on and as of the date hereof (except representations and
warranties  which  expressly  relate  solely to an earlier  date or time,  which
representations  and  warranties  shall  be true  and  correct  on and as of the
specific dates or times referred to therein);

          (b) to the Borrower's knowledge, no event or condition has occurred or
exists which,  with the giving of notice or the passage of time, or both,  would
constitute an Event of Default under any of the Loan Documents;

                                      -5-

<PAGE>

          (c) the copies of the  Borrower's  Certificate  of  Incorporation  and
Bylaws  most  recently  delivered  to the Bank have not been  amended,  revised,
supplemented,  restated  or changed in any way since their  respective  dates of
adoption and are still in full force and effect; and

         (d)  the  execution  and  delivery  of  this  Amendment  No.  5 and the
consummation of the transactions  contemplated hereby and by the Bridge Note and
any other  documents  executed by the  Borrower  required to be delivered to the
Bank in  connection  with  this  Amendment  No. 5 have  been  duly  and  validly
authorized by the Borrower and all such documents together constitute the legal,
valid and binding agreement of the Borrower, enforceable against the Borrower in
accordance with their respective terms.

     13. CONDITIONS.  The Bank's obligation to make any Advance under the Bridge
Loan is subject to the  conditions  set forth in the Loan  Agreement  and to the
following conditions as of the date of this Amendment:

         (a) Authorized Documents. The Borrower shall have furnished to the Bank
certified  copies of  resolutions  of its  board of  directors  authorizing  the
execution of this Amendment, the Bridge Note and the Warrant Agreement;

         (b) Legal  Opinion.  The  Borrower  shall have  furnished to the Bank a
legal opinion in form and substance satisfactory to the Bank; and

         (c)  Effective  Date.  The Borrower has executed  this  Amendment,  the
Bridge Loan Note, the Warrant Agreement and any other documentation  required by
the Bank on or before June 30, 2000.

     14. REIMBURSEMENT OF EXPENSES.  The Borrower shall reimburse the Bank, upon
the execution of this  Amendment No. 5, and otherwise on demand,  all reasonable
and necessary  costs and expenses  incurred by the Bank in  connection  with the
preparation,   negotiation  and  delivery  of  this  Amendment  No.  5  and  any
modifications  hereto. The obligations of the Borrower to pay expenses hereunder
are in addition to, and not in lieu of, any similar obligations set forth in the
Loan Agreement.

     15.  COUNTERPARTS.  This  Amendment  No. 5 may be  executed  in one or more
counterparts by any party hereto in separate counterparts, each of which when so
executed and delivered to the other party shall be deemed an original.  All such
counterparts together shall constitute one and the same instrument.

     16.  LIMITATION OF  AMENDMENT.  This  Amendment No. 5 shall not,  except as
expressly set forth above,  serve to  supplement or amend the Loan  Agreement or
the other Loan  Documents,  which Loan  Agreement and the Loan  Documents  shall
remain in full force and effect as amended hereby.

                                      -6-

<PAGE>

     WITNESS the due execution of this  Amendment  No. 5 to Loan  Agreement as a
document under seal, as of the date first written above.

ATTEST:                                  INFORMAX, INC.

By:  /s/ Joseph E. Lehnen                By: /s/ Alex Titomirov        (SEAL)
     ------------------------                --------------------------

Print Name: Joseph E. Lehnen             Print Name: Alex Titomirov
            -----------------                        --------------

Title:      CFO                          Title:        CEO/Chair
      -----------------------                  --------------------

                                         PNC BANK,
                                         NATIONAL ASSOCIATION

                                         By: /s/ Katharine Kappler     (SEAL)
                                             --------------------------

                                         Print Name: Katharine Kappler
                                                     ------------------

                                         Title:     Managing Director
                                               ------------------------

                                      -7-

<PAGE>

                                   Exhibit A

                                  Bridge Note

<PAGE>

                                   Exhibit B

                           Warrant Purchase Agreement

Source: [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00011-of-00352.parquet"}, [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00011-of-00352.parquet"}]]