PERSEPTIVE BIOSYSTEMS INC
S-3, 1996-08-30
LABORATORY ANALYTICAL INSTRUMENTS
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<PAGE>
 
    As filed with the Securities and Exchange Commission on August 30, 1996.
                                                 Registration No. 

================================================================================

                      SECURITIES AND EXCHANGE COMMISSION
                            Washington, D.C. 20549

                                   FORM S-3
            REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933

                          PERSEPTIVE BIOSYSTEMS, INC.
            (Exact name of registrant as specified in its charter)
                                _______________


                           500 OLD CONNECTICUT PATH
                        FRAMINGHAM, MASSACHUSETTS 01701
    DELAWARE                    (508) 383-7700                 04-2987616
(State or other              (Address, including            (I.R.S. Employer  
 jurisdiction of            zip code, and telephone        Identification No.) 
incorporation or             number, including area        
  organization)              code, of registrant's         
                         principal executive offices)     
  
                            NOUBAR B. AFEYAN, PH.D.
                            CHIEF EXECUTIVE OFFICER
                          PERSEPTIVE BIOSYSTEMS, INC.
                           500 OLD CONNECTICUT PATH
                             FRAMINGHAM, MA 01701
                                (508) 383-7700
           (Name, address, including zip code, and telephone number,
                  including area code, of agent for service)
                                _______________
                                   Copy to:

                              RUFUS C. KING, ESQ.
                        TESTA, HURWITZ & THIBEAULT, LLP
                                125 HIGH STREET
                               HIGH STREET TOWER
                          BOSTON, MASSACHUSETTS 02110
                                (617) 248-7000

  APPROXIMATE DATE OF COMMENCEMENT OF PROPOSED SALE TO THE PUBLIC: As soon as
      practicable after the Registration Statement has become effective.
                                _______________

     If the only securities being registered on this form are being offered
pursuant to dividend or interest reinvestment plans, please check the following
box.[_]

     If any of the securities being registered on this form are to be offered on
a delayed or continuous basis pursuant to Rule 415 under the Securities Act of
1933, other than securities offered only in connection with dividend or interest
reinvestment plans, check the following box.[X]

     If this form is filed to register additional securities for an offering
pursuant to Rule 462(b) under the Securities Act of 1933, please check the
following box and list the Securities Act registration statement number of the
earlier effective registration statement for the same offering.[_]

     If this form is a post-effective amendment filed pursuant to Rule 462(c)
under the Securities Act of 1933, check the following box and list the
Securities Act registration statement number of the earlier effective
registration statement for the same offering.[_]

     If delivery of the prospectus is expected to be made pursuant to Rule 434
under the Securities Act of 1933, please check the following box.[_]

                                _______________

<TABLE>
<CAPTION>
==============================================================================================
                                        Proposed             Proposed
                                         maximum              maximum
  Title of shares   Amount to be    offering price per       aggregate         Amount of
 to be registered    registered         share(1)         offering price(1)  registration fee
- ----------------------------------------------------------------------------------------------
<S>                 <C>             <C>                  <C>                <C>
Common Stock,        2,579,286       $7.25                  $18,699,824       $6,448.22
par value
$.01 per
share...           
- ----------------------------------------------------------------------------------------------
</TABLE>

(1)  Estimated solely for the purpose of calculating the registration fee
     pursuant to Rule 457(c) based on the average of the high and low prices of
     the Common Stock as reported on the Nasdaq National Market on August 27,
     1996.


     THE REGISTRANT HEREBY AMENDS THIS REGISTRATION STATEMENT ON SUCH DATE OR
DATES AS MAY BE NECESSARY TO DELAY ITS EFFECTIVE DATE UNTIL THE REGISTRANT SHALL
FILE A FURTHER AMENDMENT WHICH SPECIFICALLY STATES THAT THIS REGISTRATION
STATEMENT SHALL THEREAFTER BECOME EFFECTIVE IN ACCORDANCE WITH SECTION 8(A) OF
THE SECURITIES ACT OF 1933 OR UNTIL THIS REGISTRATION STATEMENT SHALL BECOME
EFFECTIVE ON SUCH DATE AS THE COMMISSION, ACTING PURSUANT TO SAID SECTION 8(A),
MAY DETERMINE.
================================================================================
<PAGE>
 
INFORMATION CONTAINED HEREIN IS SUBJECT TO COMPLETION OR AMENDMENT. A 
REGISTRATION STATEMENT RELATING TO THESE SECURITIES HAS BEEN FILED WITH THE 
SECURITIES AND EXCHANGE COMMISSION. THESE SECURITIES MAY NOT BE SOLD NOR MAY 
OFFERS TO BUY BE ACCEPTED PRIOR TO THE TIME THE REGISTRATION STATEMENT BECOMES 
EFFECTIVE. THIS PROSPECTUS SHALL NOT CONSTITUTE AN OFFER TO SELL OR THE 
SOLICITATION OF AN OFFER TO BUY NOR SHALL THERE BE ANY SALE OF THESE SECURITIES 
IN ANY STATE IN WHICH SUCH OFFER, SOLICITATION OR SALE WOLD BE UNLAWFUL PRIOR TO
REGISTRATION OR QUALIFICATION UNDER THE SECURITIES LAWS OF ANY SUCH STATE.


                  Subject to Completion:  Dated August 30, 1996


                               2,579,286 Shares

                          PERSEPTIVE BIOSYSTEMS, INC.

                                 Common Stock

                           Par Value $.01 Per Share
                                _______________

     This Prospectus relates to the resale of up to 2,579,286 shares (the
"Shares") of Common Stock, par value $.01 per share (the "Common Stock"), of
PerSeptive Biosystems, Inc. (the "Company") held by certain selling shareholders
(the "Selling Shareholders") which Shares were issued by the Company in a
private placement on August 16, 1996. See "Selling Shareholders." The Shares may
be offered from time to time in transactions on the Nasdaq National Market, in
negotiated transactions, through the writing of options on the Shares, or a
combination of such methods of sale, at fixed prices that may be changed, at
market prices prevailing at the time of sale, at prices related to such
prevailing market prices or at negotiated prices. See "Plan of Distribution."

     The Company will not receive any of the proceeds from the sale of the
Shares. The Company has agreed to bear all expenses (other than underwriting
discounts and selling commissions, if any, and fees and expenses of counsel or
other advisors to the Selling Shareholders) in connection with the registration
and sale of the Shares being registered hereby. The Company has agreed to
indemnify the Selling Shareholders against certain liabilities, including
liabilities under the Securities Act of 1933, as amended (the "Act"), as
underwriter or otherwise.

     The Company's Common Stock is quoted on the Nasdaq National Market under
the symbol "PBIO." On August 27, 1996, the last reported sale price for the
Common Stock was $7.125 per share.
                            _______________

     THE COMMON STOCK OFFERED HEREBY INVOLVES A HIGH DEGREE OF RISK. SEE "RISK
FACTORS" BEGINNING ON PAGE 6.
                                _______________

     THESE SECURITIES HAVE NOT BEEN APPROVED OR DISAPPROVED BY THE SECURITIES
     AND EXCHANGE COMMISSION OR ANY STATE SECURITIES COMMISSION NOR HAS THE
     SECURITIES AND EXCHANGE COMMISSION OR ANY STATE SECURITIES COMMISSION
     PASSED UPON THE ACCURACY OR ADEQUACY OF THIS PROSPECTUS. ANY REPRESENTATION
     TO THE CONTRARY IS A CRIMINAL OFFENSE.

                                _______________

                The date of this Prospectus is September __, 1996.
                                                        
<PAGE>
 
                             AVAILABLE INFORMATION

     The Company is subject to the informational requirements of the Securities
Exchange Act of 1934, as amended (the "Exchange Act"), and in accordance
therewith files reports, proxy statements and other information with the
Securities and Exchange Commission (the "Commission"). Such reports, proxy
statements and other information filed by the Company with the Commission
pursuant to the informational requirements of the Exchange Act may be inspected
and copied at the public reference facilities maintained by the Commission at
Judiciary Plaza, Room 1024, 450 Fifth Street, N.W., Washington, D.C. 20549, and
at the following regional offices of the Commission: Seven World Trade Center,
13th Floor, New York, New York 10048 and Citicorp Center, 500 West Madison
Avenue, Suite 1400, Chicago, Illinois 60611-2511. Copies of such material can
also be obtained from the Public Reference Section of the Commission at
450 Fifth Street, N.W., Washington, D.C. 20549 at prescribed rates. The Common
Stock of the Company is traded on the Nasdaq National Market, and such reports,
proxy statements and other information may also be inspected at the offices of
The Nasdaq Stock Market, Inc., Reports Section, 1735 K Street, N.W., Washington,
D.C. 20006. This Prospectus does not contain all of the information set forth in
the Registration Statement and exhibits thereto which the Company has filed with
the Commission under the Securities Act of 1933, as amended (the "Securities
Act"), and to which reference is hereby made.

     The Commission also maintains a Web site that contains reports, proxy and
information statements and other information regarding registrants that file
electronically with the Commission. The address of such site is http:
//www.sec.gov.

     The Company has filed with the Commission a Registration Statement on
Form S-3 (including all amendments thereto, the "Registration Statement") under
the Securities Act with respect to the Common Stock offered hereby. This
Prospectus does not contain all of the information set forth in the Registration
Statement, certain parts of which are omitted in accordance with the rules and
regulations of the Commission. For further information regarding the Company and
the Shares offered hereby, reference is hereby made to the Registration
Statement and to the exhibits and schedules filed therewith. Statements
contained in this Prospectus regarding the contents of any agreement or other
document filed as an exhibit to the Registration Statement are not necessarily
complete, and in each instance reference is made to the copy of such agreement
filed as an exhibit to the Registration Statement, each such statement being
qualified in all respects by such reference. The Registration Statement,
including the exhibits and schedules thereto, may be inspected at the public
reference facilities maintained by the Commission at 450 Fifth Street, N.W.,
Washington, D.C. 20549 and copies of all or any part thereof may be obtained
from such office upon payment of the prescribed fees.

                      DOCUMENTS INCORPORATED BY REFERENCE

     The following documents filed by the Company with the Commission (File No.
0-20032) are incorporated by reference herein, except as superseded or modified
herein:

     1.   Annual Report on Form 10-K for the year ended September 30, 1995, as
amended.

                                      -2-
<PAGE>
 
     2.   Current Report on Form 8-K dated November 1, 1995 regarding the
definitive agreement by the Company to acquire PerSeptive Technologies II
Corporation.

     3.   Quarterly Report on Form 10-Q for the quarterly period ended December
31, 1995.

     4.   Current Report on Form 8-K dated January 9, 1996 relating to the
Company's pending lawsuit against Pharmacia Biotech, Inc., Sepracor Inc. and
BioSepra Inc.

     5.   Current Report on Form 8-K dated February 8, 1996 relating to the
commencement of the Company's exchange offer for all of the outstanding units of
PerSeptive Technologies II Corporation.

     6.   Current Report on Form 8-K dated February 29, 1996 relating to a
special meeting of the Company's stockholders at which the issuance of
securities to acquire PerSeptive Technologies II Corporation was approved.

     7.   Current Report on Form 8-K dated March 8, 1996 relating to the
acceptance by the Company of all outstanding units of PerSeptive Technologies II
Corporation validly tendered and not withdrawn in the Company's exchange offer
to the stockholders of PerSeptive Technologies II Corporation.

     8.   Quarterly Report on Form 10-Q for the quarterly period ended March 31,
1996.

     9.   Proxy Statement for the Company's Annual Meeting of Shareholders held
on May 6, 1996.

     10.  Current Report on Form 8-K dated June 28, 1996 relating to the license
of certain technology to ChemGenics Pharmaceuticals Inc. in exchange for stock
in that company.

     11.  Quarterly Report on Form 10-Q for the quarterly period ended June 30, 
1996.

     12. Current Report on Form 8-K dated August 16, 1996 relating to the
private placement of shares of Common Stock of the Company and the redemption of
shares of the Company's non-voting Redeemable Preferred Stock held by Millipore
Corporation.
     
     13.  The description of the Company's Common Stock, $.01 par value per
share, contained in the Registration Statement on Form 8-A filed under the
Exchange Act and declared effective on May 29, 1992, including any amendment or
reports filed for the purpose of updating such description.

     14.  Current Report on Form 8-K dated October 8, 1993, as amended, filed
pursuant to the Exchange Act, relating to the Company's acquisition of Vestec
Corporation.

     15.  Current Report on Form 8-K dated October 15, 1993, as amended, filed
pursuant to the Exchange Act, relating to the Company's acquisition of the In
Vitro Business of Advanced Magnetics, Inc.

     16.  Current Report on Form 8-K dated August 22, 1994, as amended, filed
pursuant to the Exchange Act, relating to the Company's acquisition of the
assets and the business of the Biosearch Division of Millipore Corporation.

                                      -3-
<PAGE>

 
          All documents filed by the Company pursuant to Sections 13(a), 13(c),
14 or 15(d) of the Exchange Act after the date of this Prospectus and prior to
the termination of the offering made hereby shall be deemed to be incorporated
by reference in this Prospectus and to be a part hereof from the date of filing
such documents.

     Any statement contained in a document incorporated or deemed to be
incorporated by reference herein shall be deemed to be modified or superseded
for purposes of this Prospectus to the extent that a statement contained herein
or in any other subsequently filed document which also is or is deemed to be
incorporated by reference herein modifies or supersedes such statement. Any
statement so modified or superseded shall not be deemed, except as so modified
or superseded, to constitute a part of this Prospectus.

     The Company will provide without charge to each person to whom this
Prospectus is delivered, upon the written or oral request of any such person, a
copy of any document described above (other than exhibits). Requests for such
copies should be directed to Jeffrey R. Moore, Vice President-Treasury
Operations, at the principal executive offices of the Company: 500 Old
Connecticut Path, Framingham, Massachusetts 01701, telephone (508) 383-7700.
Unless the context otherwise requires, references in this Prospectus to the
"Company" or "PerSeptive" refer to PerSeptive Biosystems, Inc. and its
subsidiaries.

                                      -4-
<PAGE>
 
                                  THE COMPANY

OVERVIEW

     The Company develops, manufactures and markets proprietary products and
systems for the purification, analysis and synthesis of biomolecules. The
Company's enabling products are used in the life sciences industry to reduce the
time and cost required for the development and manufacture of
biopharmaceuticals. The Company's current and planned products are based on its
patented core technologies in the fields of chromatography, immunoassay, solid-
phase synthesis, rational surface design, biological mass spectrometry and
magnetic separations.

     The Company was incorporated in Massachusetts in November 1987 and was
reincorporated in Delaware in May 1989. The Company's executive offices are
located at 500 Old Connecticut Path, Framingham, Massachusetts 01701, and its
telephone number is (508)383-7700.

RECENT DEVELOPMENTS

     Acquisition of PerSeptive Technologies II Corporation. In March 1996, the
Company completed its acquisition of PerSeptive Technologies II Corporation
("PTC-II"), which was organized in 1993 to accelerate research and development
of the application of the Company's core technologies to certain commercial
opportunities in large life science markets. Following the successful completion
of an exchange offer for the 2,645,000 outstanding units of PTC-II, the Company
acquired 2,603,125 of such units. The PTC-II shareholders who participated in
the exchange offer exchanged their units for 2,603,125 shares of the Company's
Common Stock and 2,603,125 new Class I Warrants to purchase the Company's Common
Stock exercisable until August 8, 1997 at an exercise price per share of $13.50.
On March 13, 1996, PTC-II became a wholly owned subsidiary of the Company. Each
of the remaining 41,875 shares of callable common stock of PTC-II not exchanged
in the exchange offer were automatically converted into a right to receive one
share of the Company's Common Stock. As of the date hereof 36,475 rights were
exchanged for an equivalent number of shares of the Company's Common Stock. The
total value of the Common Stock issued in the exchange offer was approximately
$16 million based on the market value of the Common Stock on March 8, 1996. This
transaction has been accounted for as a purchase and the Company has recorded an
in-process research and development charge of approximately $6.8 million which
represents the value of acquired technologies which have not reached
commercialization.

     ChemGenics Transaction.  Effective as of June 28, 1996, the Company
completed a transaction with ChemGenics Pharmaceuticals Inc. ("ChemGenics")
(formerly, Myco Pharmaceuticals Inc.), in which the Company transferred certain
assets and employees of the Company's drug discovery program (acquired through
PTC-II) and entered into a non-exclusive license with ChemGenics, licensing the
Company's technology in the field of drug discovery to ChemGenics in exchange
for shares of ChemGenics' Common Stock equal to 40% of its fully diluted capital
stock, plus warrants to purchase, for a period of four years, additional shares
of Common Stock at $5.00 per share equal to 10% of such fully diluted amount.
The transaction will combine the Company's proprietary technology in the field
of drug discovery with ChemGenics' gene technologies.

     Private Placement of Shares of Common Stock.  On August 16, 1996, the 
Company completed a private placement of 2,579,286 shares of Common Stock, $.01 
par value, at a purchase price equal to $7.00 per share.  The shares were 
offered only to "accredited investors" (as defined in Regulation D).  The 
Company received net proceeds of approximately $17 million after deducting 
estimated fees and expenses of the transaction.  The Company intends to use the 
net proceeds of this private placement for working capital and other general 
corporate purposes.
                                      -5-
<PAGE>
 
                                 RISK FACTORS

     In addition to the other information in this Prospectus, the following
factors should be considered carefully in evaluating the Company and its
business before acquiring the Shares offered hereby. This Prospectus contains
forward-looking statements which involve risks and uncertainties. The Company's
actual results could differ materially from those anticipated in these forward-
looking statements as a result of certain factors, including those set forth in
the following risk factors and in the Company's filings with the Commission.

     Potential Downward Fluctuations in Operating Results.  The Company's
operating results may vary significantly from quarter to quarter or year to
year, depending on factors such as the timing of biopharmaceutical development
and commercialization programs of the Company's customers, the timing of
increased research and development and sales and marketing expenses, the timing
and size of orders, the introduction of new products by the Company and the
capital resources of the Company's customers. The Company's current and planned
expense levels are based in part on its expectations as to future revenue.
Consequently, revenue or profits may vary significantly from quarter to quarter
or year to year and revenue or profits in any period will not necessarily be
predictive of results in subsequent periods.

     Additional Financing Requirements. The Company believes additional long-
term financing will be required for the development of some of its future
planned product introductions and to support its planned operations and capital
expenditures in its core business relating to the purification, analysis and
synthesis of biomolecules. The Company may seek to raise additional capital
through equity or debt financing or to enter into corporate partnering
arrangements. Such financings may result in dilution to certain existing
shareholders and there can be no assurance that capital will be available or
that terms acceptable to the Company will be reached.

     History of Operating Losses and Uncertainty of Future Profitability.  To
date, the Company has not achieved profitability in any fiscal year. There can
be no assurance that the Company will achieve or maintain profitability or that
its revenue growth can be sustained in the future.

     SEC Investigation.  In November 1994, the Commission informed the Company
that the Commission had undertaken an informal investigation related to the
Company. The Commission advised the Company in May 1995 that it had obtained a
formal order of investigation so that, among other matters, it may utilize
subpoena powers to obtain information relevant to its inquiry. The Commission
has and may in the future utilize its subpoena powers to obtain information
variously from officers, directors and employees of the Company and from persons
not presently associated with the Company. If, after completion of its
investigation, the Commission finds that violations of the federal securities
laws have occurred, the Commission has the authority to order persons to cease
and desist from committing or causing such violations and any future violations.
The Commission may also seek administrative, civil and criminal fines and
penalties and injunctive relief. The Department of Justice has the authority in
respect of criminal matters. The Company has been cooperating fully with the
Commission in its investigation. There can be no assurance as to the timeliness
of the completion of this investigation, or as to the final result thereof, and
no assurance can be given that the 

                                      -6-
<PAGE>

 
final result of the investigation will not have a material adverse effect on the
Company. See "Legal Proceedings."

     Need to Integrate Acquisitions.  In recent years, the Company has made
several acquisitions that have increased the number of the Company's employees,
the scope of its business, or both. The Company may make additional acquisitions
in the future. The success of these acquisitions will depend on a number of
factors, including the ability of the Company's management to integrate the
administrative, manufacturing and sales operations of the acquired businesses
with those of the Company, to retain key personnel of the acquired businesses,
to reduce costs and to preserve and expand the sales of the products of the
acquired businesses. There can be no assurance that the Company will be able to
successfully operate these acquired businesses or that the Company will not
experience losses as a result of these acquisitions. With respect to the
recently completed acquisition of PTC-II, the success of the combined businesses
will depend, in part, on the continued availability of funding sources for the
research and development projects of the Company and PTC-II. The Company has
recently licensed certain of the technology acquired from PTC-II to ChemGenics
in exchange for stock in that company. If other research and development
programs formerly funded by PTC-II are continued by the Company, they will be
required to be funded in total by the Company and it will be required to rely on
its own resources or seek alternative sources of capital and/or collaborative
funding. There is no assurance that sufficient sources of capital and other
funding will be available to the Company in the near term or long term to fund
all of the Company's current research and development programs and those
acquired from PTC-II.

     Uncertainties Associated with Expansion of Marketing and Manufacturing
Operations.  The Company intends to continue expanding rapidly its sales and
marketing efforts in the United States and other countries. The Company's
ability to accomplish this objective is dependent on many factors, including,
among others: attracting and retaining a significant number of additional sales
and marketing professionals; expanding foreign sales operations; and developing
distributor relationships in certain markets. This continued expansion will
involve significant additional expense and the risks inherent in integrating new
sales and marketing personnel into the Company's existing organization.
Increasing sales may also require expansion of the Company's manufacturing
capabilities, which would require significant capital expenditures and
management attention. There can be no assurance that the Company will be able to
accomplish its sales, marketing and manufacturing objectives.

     Potential Costs Associated With Patent Litigation.  Patent litigation is
widespread in the biotechnology industry and, in general, it is not possible to
predict how any such litigation would affect the Company's business. The Company
has sued two competitors for infringement of the Company's patents relating to
Perfusion Chromatography. The defendants in that suit are seeking to have these
patents declared invalid and have asserted counterclaims against the Company.
The litigation has been expanded to cover an additional patent in which the
Company has been granted rights. The Company expects to incur substantial
additional expenses relating to these lawsuits. There can be no assurance that
the outcome of the litigation will not have a material adverse effect on the
Company. See "Legal Proceedings."

     Patent and License Uncertainties.  Proprietary rights relating to the
Company's products will be protected from unauthorized use by third parties only
to the extent that they are covered by valid 

                                      -7-
<PAGE>

 
and enforceable patents or are maintained in confidence as trade secrets. There
can be no assurance that any pending patent applications filed by the Company
will result in patents being issued or that any patents now or hereafter owned
by the Company will afford protection against competitors. If the Company
participates in interference or other proceedings under the jurisdiction of the
U.S. Patent and Trademark Office, such proceedings could result in substantial
costs to the Company. Competitors, including those with substantially greater
resources than those of the Company, may initiate litigation to challenge the
validity of the Company's patents. Others may use their resources to design
comparable products that do not infringe the Company's patents. There may also
be pending or issued patents, of which the Company is not aware, held by parties
not affiliated with the Company that relate to the Company's products or
technology. The Company may need to acquire licenses to, or contest the validity
of, any such patents. It is likely that significant funds would be required to
contest the validity of any such patents. There can be no assurance that any
license required under any such patent would be made available on acceptable
terms or that the Company would prevail in any such contest.

     Limited Protection of Trade Secrets.  Certain of the technology that may be
used in the Company's products is not covered by any patent or patent
application. There also can be no assurance that the Company's non-disclosure
agreements with its employees and consultants will provide meaningful protection
for the Company's trade secrets or other proprietary information. In the absence
of patent protection, the Company's business may be adversely affected by
competitors that independently develop functionally equivalent technology.

     Dependence of Customers on Government Sponsored Research.  A substantial
portion of the Company's sales are to customers at universities or research
laboratories whose funding is dependent upon both the level and timing of
funding from government sources. The sensitivity of sales to uncertainties in
such funding is greatest when capital expenditures are involved, particularly
instruments at the high-price end of the Company's product offerings. As a
result, the timing and amount of revenues from these sources may vary
significantly due to factors that can be difficult to forecast.

     Intense Competition and Risk of Technological Obsolescence.  The Company
encounters, and expects to continue to encounter, intense competition in the
sale of its current and future products. There can be no assurance that
developments by others will not render the Company's products or technologies
obsolete or non-competitive. Many of the Company's competitors and potential
competitors have substantially greater resources, manufacturing and marketing
capabilities, research and development staff and production facilities than
those of the Company.

     Government Regulation May Slow Product Introduction and Sales.  The
Company's purification, analysis and synthesis products are not currently
subject to regulation by the U.S. Food and Drug Administration ("FDA"). However,
FDA regulations apply to the processes and production facilities used by the
Company's customers to manufacture biopharmaceutical products. Any material
change by a biopharmaceutical company in its manufacturing process or equipment
could necessitate additional FDA review and approval. Such requirements may make
it more difficult for the Company to sell its products to customers that have
already applied for or obtained FDA licenses for production processes using
different equipment and supplies. The Company's clinical diagnostic products are
subject to pre-marketing clearance or approval by the FDA in the United States
and by similar agencies 

                                      -8-
<PAGE>

 
in other countries; however the Company presently has no pending FDA clearances
or approvals. The process for obtaining such clearances and approvals can be
both lengthy and costly. There can be no assurance that necessary, timely
clearances and approvals will be granted for products developed by the Company.

     Currency Exchange Risks; International Sales and Operations.  The Company's
sales to customers outside of the United States account for a significant
percentage of its revenue. A substantial portion of the Company's international
sales are denominated in foreign currencies, while its costs are denominated
principally in U.S. dollars and, to a lesser extent, in Deutschmarks. Decreases
relative to the U.S. dollar in the value of currencies in which sales are made
would result in reduced sales and profit to the extent that they are not offset
by price increases. With respect to the Company's sales that are U.S. dollar-
denominated, such decreases could make their products less price-competitive.
International sales and operations may also be adversely affected by the
imposition of governmental controls, export license requirements, restrictions
on the export of critical technology, political and economic instability, trade
restrictions, changes in tariffs and taxes, difficulties in staffing and
managing international operations and general economic conditions.

     Need to Attract and Retain Key Employees.  The Company is highly dependent
on the principal members of its management and scientific staff. The loss of the
services of one or more of these key employees could have a material adverse
effect on the Company. The Company believes that its future success will depend
in large part upon its ability to attract and retain highly skilled scientific,
managerial and marketing personnel. Competition for such personnel is intense.
There can be no assurance that the Company will be successful in attracting or
retaining such personnel.

     Risk of Product Liability Claims; Limited Insurance Coverage.  The testing,
marketing and sale of biomolecule purification, analysis and synthesis products
entails an inherent risk of product liability, and there can be no assurance
that product liability claims will not be asserted against the Company.
Furthermore, there can be no assurance that the Company will continue to be able
to obtain its current limited product liability insurance coverage on reasonable
terms or that current insurance or insurance subsequently obtained will provide
adequate coverage against any or all potential claims.

     Potential Adverse Effects of the Use of Hazardous Materials.  Research and
development processes involve the controlled use of laboratory quantities of
hazardous materials. The Company's chemical manufacturing operations use and
dispose of significant quantities of chemicals which may be considered hazardous
under, and are subject to, applicable federal, state, local and foreign laws and
regulations governing the use, manufacture, storage, handling and disposal of
such material and certain waste products. There can be no assurance that the
Company will not be required to incur significant costs to comply with
environmental laws and regulations, nor that the operations, business or assets
of the Company will not be materially adversely affected by current or future
environmental laws or regulations.

     Possible Volatility of Stock Price.  From time to time there may be
significant volatility in the market price of the Company's Common Stock because
of factors unrelated, as well as related, to the Company's operating
performance.

                                      -9-
<PAGE>

 
     Anti-Takeover Provision; Possible Issuance of Preferred Stock.  The
Company's Shareholder Rights Plan and certain provisions of the Company's
Amended and Restated Certificate of Incorporation, Amended and Restated By-Laws,
as amended, and Delaware law could discourage potential acquisition proposals
and could delay or prevent a change in control of the Company. The Company's
Amended and Restated Certificate of Incorporation and Amended and Restated By-
Laws, as amended, contain provisions that divide the Board of Directors of the
Company into three classes, so that directors are subject to re-election every
three years, that require the vote of 75% of the Company's shareholders to
remove a director without cause and that prohibit shareholder action by written
consent. The Company's Shareholder Rights Plan could diminish the opportunities
for a shareholder to participate in tender offers, including tender offers at a
price above the then current market value of the Common Stock. These provisions
may discourage acquisition bids for the Company. Such provisions could limit the
price that investors might be willing to pay in the future for shares of the
Company's Common Stock. Such provisions may also inhibit fluctuations in the
market price of the Common Stock that could result from takeover attempts. In
addition, the Board of Directors, without further shareholder approval, may
issue Preferred Stock that could have the effect of delaying, deterring or
preventing a change in control of the Company. The issuance of Preferred Stock
could also adversely affect the voting power of the holders of Common Stock,
including the loss of voting control to others. The Company is subject to the
provisions of Section 203 of the Delaware General Corporation Law. Subject to
certain exceptions, Section 203 prohibits a publicly held Delaware corporation
from engaging in a "business combination" with an "interested stockholder" for a
period of three years after the date of the transaction in which the person
became an interested stockholder, unless the interested stockholder attained
such status with the approval of the Board of Directors or unless the business
combination is approved in a prescribed manner. A "business combination"
includes mergers, asset sales and other transactions resulting in a financial
benefit to the interested stockholder. Subject to certain exceptions, an
"interested stockholder" is a person who, together with affiliates and
associates, owns, or within three years did own, 15% or more of the
corporation's voting stock. All of the foregoing provisions could have the
effect of making it more difficult for a third party to acquire, or of
discouraging a third party from acquiring, control of the Company.

     No Dividends.  The Company has never paid cash dividends on its Common
Stock. Payment of dividends is within the discretion of the Board of Directors
and will depend upon the Company's earnings, capital requirements, financial
condition and other relevant factors. It is the Company's intention to retain
earnings, if any, to finance the operation and expansion of its business and
therefore, it does not expect to pay any dividends on its Common Stock in the
foreseeable future.

                                      -10-
<PAGE>
 
                             SELLING SHAREHOLDERS


     The following table sets forth certain information with respect to the
Shares held by each Selling Shareholder. The Shares may be offered from time to
time by any of the Selling Shareholders. See "Plan of Distribution."

<TABLE>
<CAPTION>
                                             Shares Beneficially   
                                                Owned Prior to         Shares           Shares Beneficially
                                                  Offering             Offered       Owned After Offering (3)
                                                  -----------          -------       ------------------------  
 
Name(1)                                       Number     Percent(2)       Number        Number     Percent(2)
- ----                                          ------     ----------       ------        ------     ----------  
                                                                                              
<S>                                        <C>           <C>             <C>            <C>        <C> 
Peter L. Getz                               50,000         *               25,000         25,000      *
Armen Partners, L.P.                       815,000         4%             300,000        515,000    2.5%
John G. Nardi IRA                           15,000         *               15,000           0         *
Cerinox Finance, Inc.                      160,000         *              150,000         10,000      *
Quasar International Partners, C.V.,
by Chancellor Trust Company,
as manager and attorney-in-fact            391,500         2%             300,000         91,500      * 
James J. Pinto                              20,000         *               20,000           0         *
Hare & Co.                                   8,000         *                8,000           0         *
Orefund (4)                                975,000       4.8%             292,000        683,500    3.4%
Mark Berg                                  100,000         *              100,000           0         *
Oracle International Partners, L.P.         62,500         *               56,000          6,500      *
Oracle Partners, L.P.                      375,000       1.9%             329,000         46,000      *
GSAM Oracle Fund, Inc.                     281,500       1.4%             245,000         36,500      *
Quasar International Partners, C.V.        161,500         *               70,000         91,500      *
Richard J. Sterne                           20,000         *               20,000           0         *
J. Todd Morley                              10,000         *               10,000           0         *
Phillip T. George and Judith L. George 
Ten Ent.                                    20,000         *               20,000           0         *
Egger & Co.                                 75,000         *               75,000           0         *
Dr. Phillip Frost                          150,000         *              150,000           0         *
Robert K. Jermain                           14,286         *               14,286           0         *
S.K.H. Bessent                              30,000         *               30,000           0         *
CS First Boston Corporation                300,000       1.5%             300,000           0         *
Gerlach & Co.                               40,000         *               40,000           0         *
Jon P. Hedley                               10,000         *               10,000           0         *
</TABLE>

_____________________

* Less than 1%

(1) The persons named in the table have sole voting and investment power with
respect to all shares shown as beneficially owned by them. Beneficial holdings
are based on questionnaires completed in connection with the August 16, 1996
private placement.

(2) As of August 26, 1996 there were 20,047,632 shares of Common Stock 
outstanding.

(3) Assumes that the Selling Shareholders will sell all of the Shares
registered hereunder. The Selling Shareholders may sell all or any part of their
Shares pursuant to this Prospectus.

(4) Includes warrants for the purchase of 310,000 shares of Common Stock of the
Company.

     Other than as described below, to the best of the Company's knowledge, none
of the Selling Shareholders had any material relationship with the Company or
any of its affiliates within the three year period ending on the date of this
Prospectus.

     The sole general and limited partner of Armen Partners, L.P. is Dr. Garo H.
Armen.  Dr. Armen was a director of PTC-II from December 1993 until it was 
acquired by the Company in March 1996.

                                      -11-
<PAGE>
 

                             PLAN OF DISTRIBUTION

     The Company will not receive any of the proceeds from this offering. The
Shares offered hereby may be sold from time to time by or for the account of any
of the Selling Shareholders or by their pledgees, donees, distributees or
transferees or other successors in interest to the Selling Shareholders. The
Shares may be sold hereunder directly to purchasers by the Selling Shareholders
in negotiated transactions; by or through brokers or dealers in ordinary
brokerage transactions or transactions in which the broker solicits purchasers;
block trades in which the broker or dealer will attempt to sell the Shares as
agent but may position and resell a portion of the block as principal;
transactions in which a broker or dealer purchases as principal for resale for
its own account; or through underwriters or agents. The Shares may be sold at a
fixed offering price, which may be changed, at the prevailing market price at
the time of sale, at prices related to such prevailing market price or at
negotiated prices. Any brokers, dealers, underwriters or agents may arrange for
others to participate in any such transaction and may receive compensation in
the form of discounts, commissions or concessions from the Selling Shareholders
and/or the purchasers of the Shares. Each Selling Shareholder will be
responsible for payment of any and all commissions to brokers.

     The aggregate proceeds to any Selling Shareholder from the sale of the
Shares offered by the Selling Shareholder hereby will be the purchase price of
such Shares less any broker's commissions.

     In order to comply with the securities laws of certain states, if
applicable, the Shares will be sold in such jurisdiction only through registered
or licensed brokers or dealers. In addition, in certain states the Shares may
not be sold unless they have been registered or qualified for sale in the
applicable state or an exemption from the registration or qualification
requirement is available and is complied with.

     Any Selling Shareholder and any broker-dealer, agent or underwriter that
participate with the Selling Shareholder in the distribution of the Shares may
be deemed to be "underwriters" within the meaning of the Securities Act, in
which event any commissions received by such broker-dealers, agents or
underwriters and any profit on the resale of the Shares purchased by them may be
deemed to be underwriting commissions or discounts under the Securities Act.

                                      -12-
<PAGE>

 
     Under applicable rules and regulations under the Exchange Act, any person
engaged in the distribution of the Shares offered hereby may not simultaneously
engage in market making activities with respect to the Shares for a period of
two business days prior to the commencement of such distribution. In addition,
and without limiting the foregoing, each Selling Shareholder will be subject to
applicable provisions of the Exchange Act and the rules and regulations
thereunder, including, without limitation, Rules 10b-2, 10b-5, 10b-6 and 10b-7,
which provisions may limit the timing of purchases and sales of the Shares by
the Selling Shareholder.

     There is no assurance that any Selling Shareholder will sell any or all of
the Shares described herein and may transfer, devise or gift such securities by
other means not described herein.

     The Company will use its best efforts to cause the registration statement
to which this Prospectus relates to become effective as promptly as is
practicable and to keep the registration statement effective until two years
from the date hereof. The Company is permitted to suspend the use of this
Prospectus in connection with sales of the Shares by holders during certain
periods of time under certain circumstances relating to pending corporate
developments and public filings with the Commission and similar events. Expenses
of preparing and filing the registration statement and all post-effective
amendments will be borne by the Company.

                               LEGAL PROCEEDINGS

     1.   On October 14, 1993, the Company filed suit against Pharmacia Biotech,
Inc., a New Jersey corporation, together with certain of its affiliates, and
their parent Pharmacia AB, a Swedish corporation (collectively, "Pharmacia"),
and Sepracor Inc., a Delaware corporation ("Sepracor"), in the United States
District Court for the District of Massachusetts (Civil Action No. 93-12237-PBS)
for willful infringement of the Company's U.S. Patents Nos. 5,019,270 and
5,228,989 (collectively, the "Patents") covering the process of Perfusion
Chromatography and the manufacture, sale and use of chromatography particles
that enable Perfusion Chromatography. This lawsuit seeks to enjoin the
defendants from infringing the Patents and asks for treble damages. On October
15, 1993, the Company filed a related action against Sepracor in the United
States District Court for the District of Massachusetts (Civil Action No. 93-
12249-PBS) in which the Company claims that Sepracor has made false and
misleading representations of fact with respect to the Company's products in
violation of applicable state and federal law. On October 12, 1993, as a result
of prior correspondence with the Company, Pharmacia filed a suit against the
Company in the United States District Court for the District of New Jersey
(Civil Action No. 93-4450 (HAA)) seeking a declaratory judgment: (i) that
Pharmacia's products do not infringe the Patents and (ii) that the Patents are
invalid and unenforceable. 

     On January 18, 1994, the United States District Court for the District of
New Jersey allowed the Company's motion to transfer all proceedings in
Pharmacia's action to the United States District Court for the District of
Massachusetts. By orders dated December 3, 1993 and March 29, 1994, the United
States District Court for the District of Massachusetts has consolidated all
three actions identified above for pretrial proceedings.

                                      -13-
<PAGE>

 
     On May 19, 1994, the United States District Court for the District of
Massachusetts allowed the Company's motion to join BioSepra Inc., which is
partially owned by Sepracor ("BioSepra"), as a party and to amend the pleadings
to assert claims against BioSepra for willful infringement of the Patents and
for false and misleading advertising. The Company's claims against BioSepra are
consolidated with claims against Sepracor and Pharmacia for pretrial
proceedings.

     On October 5, 1994, the Court allowed the Company's motion to amend its
pleadings to allege claims against Sepracor and BioSepra for infringement of
United States Patent No. 5,030,352 (the "'352 Patent"), covering novel coatings
for chromatography media, which is assigned to the Purdue Research Foundation
and exclusively licensed to the Company.

     On January 24, 1995, the U.S. Patent and Trademark Office issued a third
patent assigned to the Company, U.S. Patent No. 5,384,042, covering the
manufacture, sale and use of matrices that enable Perfusion Chromatography. On
January 25, 1995, the Company filed a complaint in the United States District
Court for the District of Massachusetts against Pharmacia, Sepracor and BioSepra
alleging willful infringement of the '042 Patent. On February 14, 1995, the
Court allowed an assented-to motion to consolidate that action, designated Civil
Action No. 95-10157-PBS, with the pending actions described above. 

     Pharmacia, Sepracor and BioSepra each have asserted counterclaims against
the Company. On February 10, 1995, Sepracor and BioSepra filed a counterclaim
against the Company alleging that its allegations that Sepracor and BioSepra
have infringed the Patents and alleged statements concerning the litigation made
to customers constitute unfair competition, commercial disparagement, unfair
trade practices allegedly in violation of Mass. Gen. Laws ch. 93A, tortious
interference with customer relationships and violation of the Lanham Act.
Sepracor and BioSepra requested relief in the form of an unspecified amount of
damages, double or treble damages to the extent permitted by Mass. Gen. Laws ch.
93A, dismissal of all claims asserted by the Company, and Sepracoras costs and
attorneys' fees. On March 6, 1995, Pharmacia filed a counterclaim alleging that
the Company's allegations that Pharmacia has infringed the Patents and alleged
statements concerning the litigation made to customers constitute unfair
competition, commercial disparagement, unfair trade practices allegedly in
violation of Mass. Gen. Laws ch. 93A, and violation of the Lanham Act. Pharmacia
requested relief in the form of an unspecified amount of damages, double or
treble damages to the extent permitted by Mass. Gen. Laws ch. 93A, dismissal of
all claims asserted by PerSeptive, and Pharmacia's costs and attorneys' fees.
Since the Court has bifurcated discovery on damages issues, Sepracor and
Pharmacia have not quantified the amount of damages sought in their respective
counterclaims. The Company has denied any liability on the counterclaims.

     On January 9, 1996, the Court entered an order denying the Company's motion
for partial summary judgment relating to the inventorship of the three Perfusion
Chromatography patents, and granting the Defendants' motions for partial summary
judgment that inventorship of those patents is improper for failure to name two
or more persons as joint inventors. The Court, however, affirmed the Company's
inventorship. On March 19, 1996, PerSeptive filed a Motion to Vacate the January
9 order and requested the Court to conduct an evidentiary hearing pursuant to 35
U.S.C. ((S)) 256 to determine whether the patents can and should be corrected by
adding additional alleged inventors and, among

                                      -14-
<PAGE>
 
other issues, if the patents can be corrected, whether the alleged additional
inventors should be stopped from asserting any rights on account of their never
having claimed to have been inventors, among other factors. On April 29, 1996,
the court denied the Motion to Vacate. An evidentiary hearing on the
inventorship issue was conducted in May and June, 1996. Post-hearing submissions
were filed by the parties in July, 1996, and closing arguments were heard by the
Court on August 8, 1996. The Company has preserved its rights of appeal on a
number of issues, including the Court's January 9, 1996 order that inventorship
of the patents was improper for failure to name additional persons as joint
inventors.

     The Company expects to incur substantial additional expenses relating to
these lawsuits. There can be no assurance that the outcome of the litigation
will not have a material adverse effect on the Company. The Company intends to
continue vigorously pursuing this litigation.

     2.   Since November 1994, the Company has been responding to informal
requests for information from the Commission relating to certain of the
Company's financial matters. In May 1995, the Company was advised by the
Commission that it had obtained a formal order of investigation so that, among
other matters, it could utilize subpoena powers to obtain information relevant
to its inquiry. The Commission has and may in the future utilize its subpoena
powers to obtain information variously from officers, directors and employees of
the Company and from persons not presently associated with the Company. If,
after completion of its investigation, the Commission finds that violations of
the federal securities laws have occurred, the Commission has the authority to
order persons to cease and desist from committing or causing such violations and
any future violations. The Commission may also seek administrative, civil and
criminal fines and penalties and injunctive relief. The Department of Justice
has the authority in respect of criminal matters. There can be no assurance as
to the timeliness of the completion of this investigation, or as to the final
result thereof, and no assurance can be given that the final result of the
investigation will not have a material adverse effect on the Company. The
Company has responded and will continue to respond to requests for information
in connection with this investigation.

                                 LEGAL MATTERS

     Certain legal matters relating to the Shares of Common Stock have been
passed upon for the Company by Testa, Hurwitz & Thibeault, LLP, Boston,
Massachusetts. Four partners of Testa, Hurwitz & Thibeault, LLP are the holders
of an aggregate of 7,734 shares of Common Stock. Two partners of Testa, Hurwitz
& Thibeault, LLP are holders of Warrants to purchase 1,000 shares of the
Company's Common Stock.

                                    EXPERTS

     The consolidated balance sheet as of September 30, 1995 and the
consolidated statements of operations, stockholders' equity and cash flows of
the Company for the year then ended, incorporated by reference in this
Prospectus, have been incorporated by reference herein in reliance on the report
of Coopers & Lybrand L.L.P., independent accountants, given on the authority of
that firm as experts in auditing and accounting.

                                      -15-
<PAGE>

 
     The consolidated financial statements of the Company as of and for each of
the two years in the period ended September 30, 1994 which have been
incorporated in this Prospectus by reference to the Annual Report on Form 10-K
for the year ended September 30, 1995, as amended, have been so incorporated in
reliance on the report of Price Waterhouse LLP, independent accountants, given
on the authority of said firm as experts in auditing and accounting.

     The balance sheets of the Biosearch Division of Millipore Corporation as of
December 31, 1992 and 1993 and the statements of operations and cash flows for
each of the three years in the period ended December 31, 1993, incorporated by
reference in this Prospectus, have been incorporated herein in reliance on the
report, which includes an emphasis of a matter paragraph regarding allocated
costs, of Coopers & Lybrand L.L.P., independent accountants, given on the
authority of that firm as experts in accounting and auditing.

     The balance sheets of the In Vitro Business of Advanced Magnetics, Inc. as
of September 30, 1993 and 1992 and the statements of operations and cash flows
for each of the three years in the period ended September 30, 1993, incorporated
by reference in this Prospectus, have been incorporated herein in reliance on
the report, which includes an emphasis of a matter paragraph regarding allocated
costs, of Coopers & Lybrand, L.L.P., independent accountants, given on the
authority of that firm as experts in accounting and auditing.

     The balance sheets of Vestec Corporation as of December 31, 1992 and 1991
and the statements of operations and cash flows for each of the three years in
the period ended December 31, 1992, incorporated by reference in this
Prospectus, have been incorporated herein in reliance on the report of Mir Fox &
Rodriguez, independent accountants, given on the authority of that firm as
experts in accounting and auditing.

                                      -16-
<PAGE>
 
================================================================================
No person has been authorized to give any information or to make any
representation other than those contained in this Prospectus in connection with
the offering made hereby, and if given or made, such information or
representation must not be relied upon as having been authorized by the Company
or by any other person. Neither the delivery of this Prospectus nor any sale
made hereunder shall, under any circumstances, create any implication that
information herein is correct as of any time subsequent to the date hereof. This
Prospectus does not constitute an offer to sell or a solicitation of any person
in any jurisdiction in which such offer or solicitation may not be lawfully 
made.
 
                             _____________________

                               TABLE OF CONTENTS

<TABLE> 
<CAPTION> 
                                                                           Page
                                                                           ----
<S>                                                                        <C> 
Available Information....................................................    2 
Documents Incorporated by Reference......................................    2
The Company..............................................................    5
Risk Factors.............................................................    6
Selling Shareholders.....................................................   11
Plan of Distribution.....................................................   12
Legal Proceedings........................................................   13
Legal Matters............................................................   15
Experts..................................................................   15 
</TABLE>

================================================================================


                               2,579,286 Shares


                            PERSEPTIVE BIOSYSTEMS,
                                     INC.



                                 Common Stock




                              __________________

                                  PROSPECTUS
                              __________________








                                September __, 1996
<PAGE>
 
                                    PART II

                    INFORMATION NOT REQUIRED IN PROSPECTUS


Item 14.  Other Expenses of Issuance and Distribution.

          The expenses (other than the underwriting discount) incurred by the
Company in connection with the issuance and distribution of the securities being
registered are as follows:

<TABLE>
<CAPTION>
                                                                       Amount*
                                                                       ------   
<S>                                                                   <C>
Securities and Exchange Commission registration fee..............     $ 6,448.22
 
Nasdaq National Market listing fee...............................     $17,500.00
 
Legal fees and expenses..........................................     $50,000.00
 
Accounting fees and expenses.....................................     $ 5,000.00
 
Miscellaneous....................................................     $ 4,000.00
                                                                      ----------
 
               Total.............................................     $82,948.22  
                                                                      ----------
</TABLE>

_______________

 * All amounts are estimated except the Securities and Exchange Commission fee
and the Nasdaq National Market listing fee.

Item 15.  Indemnification of Directors and Officers.

Delaware Law and Certain Charter and By-Law Provisions
- ------------------------------------------------------

          The Company is subject to the provisions of Section 203 of the
Delaware General Corporation Law (the "DGCL"). Section 203 prohibits a publicly
held Delaware corporation from engaging in a "business combination" with an
"interested shareholder" for a period of three years after the date of the
transaction in which the person became an interested shareholder, unless the
business combination is approved in a prescribed manner. A "business
combination" includes mergers, asset sales and other transactions resulting in a
financial benefit to the interested shareholder. Subject to certain exceptions,
an "interested shareholder" is a person who, together with affiliates and
associates, owns, or within three years did own, 15% or more of the
corporation's voting stock.

          The Company's Amended and Restated Certificate of Incorporation (the
"Charter") provides for the division of the Board of Directors into three
classes as nearly equal in size as possible with staggered three year terms. Any
director may be removed without cause only by the vote of at least

                                      II-1
<PAGE>

 
75% of the shares entitled to vote for the election of directors. The
classification of the Board of Directors could have the effect of making it more
difficult for a third party to acquire, or of discouraging a third party from
acquiring, control of the Company.

          The Charter contains certain provisions permitted under the DGCL
relating to the liability of directors. The provisions eliminate a director's
liability for monetary damages for a breach of fiduciary duty, except in certain
circumstances involving wrongful acts, such as the breach of a director's duty
of loyalty or acts or omissions which involve intentional misconduct or a
knowing violation of law. The Charter also contains provisions indemnifying its
directors and officers to the fullest extent permitted by the DGCL. The Company
believes that these provisions will assist the Company in attracting and
retaining qualified individuals to serve as directors. The Company has, in
accordance with the terms of the Charter, also entered into contractual
arrangements with each of its directors providing for indemnification of its
directors under certain circumstances.

          The Charter and the Company's Amended and Restated By-laws, as amended
(the "By-laws"), provide that any action required or permitted to be taken by
the shareholders of the Company may be taken only at a duly called annual or
special meeting of the shareholders, and that special meetings may be called
only by the Chairman of the Board of Directors, Chief Executive Officer or
President of the Company. These provisions could have the effect of delaying
until the next annual shareholders' meeting shareholder actions which are
favored by the holders of a majority of the outstanding voting securities of the
Company. These provisions may also discourage another person or entity from
making a tender offer for the Company's Common Stock, because such person or
entity, even if it acquired a majority of the outstanding voting securities of
the Company, would be able to take action as a shareholder (such as electing new
directors or approving a merger) only at a duly called shareholders' meeting,
and not by written consent.

          The Company's By-laws provide that for nominations for the Board of
Directors or for other business to be properly brought by a shareholder before a
meeting of shareholders, the shareholder must first have given timely notice
thereof in writing to the Secretary of the Company. To be timely, a
shareholder's notice generally must be delivered not less than 60 days nor more
than 90 days prior to an annual meeting. With respect to special meetings,
notice must generally be delivered not more than 90 days prior to such meeting
and not later than the later of 60 days prior to such meeting or 10 days
following the day on which public announcement of such meeting is first made by
the Company. The notice must contain, among other things, certain information
about the shareholder delivering the notice and, as applicable, background
information about each nominee or a description of the proposed business to be
brought before the meeting.

          The Charter empowers the Board of Directors, when considering a tender
offer or merger or acquisition proposal, to take into account factors in
addition to potential economic benefits to shareholders. Such factors may
include (i) comparison of the proposed consideration to be received by
shareholders in relation to the then current market price of the Company's
capital stock, the estimated current value of the Company in a freely negotiated
transaction and the estimated future value of the Company as an independent
entity; (ii) the impact of such a transaction on the employees, suppliers and
customers of the Company and its effect on the communities in which the Company
operates; and (iii) the ability of the Company to fulfill its objectives under
applicable statutes and regulations.

                                      II-2
<PAGE>

 
          The DGCL provides generally that the affirmative vote of a majority of
the shares entitled to vote on any matter is required to amend a corporation's
certificate of incorporation or by-laws, unless a corporation's certificate of
incorporation or by-laws, as the case may be, requires a greater percentage. The
Charter and the Company's By-laws will require the affirmative vote of the
holders of at least 75% of the outstanding voting stock of the Company to amend
or repeal certain of the foregoing provisions including those relating to the
classification of the Board of Directors, the removal of directors and the
prohibition against shareholder action by written consent. Such 75% shareholder
vote would be in addition to any separate class vote that might in the future be
required pursuant to the terms of any Preferred Stock that might be outstanding
at the time any such amendments are submitted to shareholders.

Item 16.  Exhibits.

          See the Exhibit Index immediately preceding the exhibits to this
Registration Statement.

Item 17.  Undertakings.

          (a)    The undersigned Registrant hereby undertakes:

          (1)    to file, during any period in which offers or sales are being
     made, a post-effective amendment to this registration statement;

          (i)    to include any prospectus required by Section 10(a)(3) of the
     Securities Act of 1933;

          (ii)   to reflect in the prospectus any facts or events arising after
     the effective date of the registration statement (or the most recent post-
     effective amendment thereof) which, individually or in the aggregate,
     represent a fundamental change in the information set forth in the
     registration statement; notwithstanding the foregoing, any increase or
     decrease in volume of securities offered (if the total dollar value of
     securities offered would not exceed that which was registered) and any
     deviation from the low or high and of the estimated maximum offering range
     may be reflected in the form of prospectus filed with the Commission
     pursuant to Rule 424(b) if, in the aggregate, the changes in volume and
     price represent no more than 20 percent change in the maximum aggregate
     offering price set forth in the "Calculation of Registration Fee" table in
     the effective registration statement;

          (iii)  to include any material information with respect to the plan of
     distribution not previously disclosed in the registration statement or any
     material change to such information in the registration statement;

               provided however, that paragraphs (a) (1) (i) and (a) (1) (ii) 
               -------- -------                                               
do not apply if the information required to be included in a post-effective
amendment by those paragraphs is contained in periodic reports filed by the
registrant pursuant to Section 13 or Section 15(d) of the Securities Exchange
Act of 1934 that are incorporated by reference in the registration statement.

                                      II-3
<PAGE>

 
          (2)    That, for the purpose of determining any liability under the
     Securities Act of 1933, each such post-effective amendment shall be deemed
     to be a new registration statement relating to the securities offered
     therein, and the offering of such securities at that time shall be deemed
     to be the initial bona fide offering thereof.
                       ---- ----                  

          (3)    To remove from registration by means of post-effective
     amendment any of the securities being registered which remain unsold at the
     termination of the offering.

          (b)    The undersigned registrant hereby undertakes that, for purposes
of determining any liability under the Securities Act of 1933, each filing of
the registrant's annual report pursuant to Section 13(a) or Section 15(d) of the
Securities Exchange Act of 1934 that is incorporated by reference in the
registration statement shall be deemed to be a new registration statement
relating to the securities offered therein, and the offering of such securities
at that time shall be deemed to be the initial bona fide offering thereof.
                                               ---- ----                  

          (c)    Insofar as indemnification for liabilities arising under the
Securities Act of 1933 may be permitted to directors, officers and controlling
persons of the registrant pursuant to the foregoing provisions, or otherwise,
the registrant has been advised that in the opinion of the Securities and
Exchange Commission such indemnification is against public policy as expressed
in the Securities Act of 1933 and is, therefore, unenforceable. In the event
that a claim for indemnification against such liabilities (other than the
payment by the registrant of expenses incurred or paid by a director, officer or
controlling person of the registrant in the successful defense of any action,
suit or proceeding) is asserted by such director, officer or controlling person
in connection with the securities being registered, the registrant will, unless
in the opinion of its counsel the matter has been settled by controlling
precedent, submit to a court of appropriate jurisdiction the question whether
such indemnification by it is against public policy as expressed in the
Securities Act of 1933 and will be governed by the final adjudication of such
issue.

                                      II-4
<PAGE>
 
                                  SIGNATURES

          Pursuant to the requirements of the Securities Act of 1933, the
Registrant certifies that it has reasonable grounds to believe that it meets all
of the requirements for filing on Form S-3 and has duly caused this Registration
Statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the Town of Framingham, Commonwealth of Massachusetts, on the
30th day of August, 1996.

                                        PERSEPTIVE BIOSYSTEMS, INC.


                                        By:  /s/ Noubar B. Afeyan
                                           --------------------------
                                           Noubar B. Afeyan
                                           Chief Executive Officer


                       POWER OF ATTORNEY AND SIGNATURES

          We, the undersigned officers and directors of PerSeptive Biosystems,
Inc., hereby severally constitute and appoint Noubar B. Afeyan, Thomas G. Ruane
and Jeffrey R. Moore, and each of them singly, our true and lawful attorneys,
with full power to them and each of them singly, to sign for us in our names in
the capacities indicated below, all pre-effective and post-effective amendments
to this Registration Statement, and generally to do all things in our names and
on our behalf in such capacities to PerSeptive Biosystems, Inc. to comply with
the provisions of the Securities Act of 1933, as amended, and all requirements
of the Securities and Exchange Commission.

          Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed by the following persons in the
capacities and on the dates indicated.

<TABLE> 
<CAPTION> 
        Signature                       Title                              Date
        ---------                       -----                              ----

<S>                             <C>                                        <C> 
/s/ Noubar B. Afeyan            Chief Executive                            August 30, 1996
- -----------------------------
Noubar B. Afeyan                Officer (Principal Executive
                                Officer), Director and Chairman
                                of the Board of Directors


/s/ John F. Smith               President and Director                     August 30, 1996
- -----------------------------
John F. Smith


/s/ Thomas G. Ruane             Senior Vice President and Chief            August 30, 1996
- -----------------------------
Thomas G. Ruane                 Financial Officer
                                (Principal Financial and
                                Accounting Officer)
</TABLE> 
<PAGE>
 
<TABLE> 
<S>                             <C>                                        <C> 
_____________________________   Director                                   August__, 1996
Daniel I.C. Wang


/s/ Edwin M. Kania, Jr.         Director                                   August 30, 1996
- -----------------------------
Edwin M. Kania, Jr.


/s/ William F. Pounds           Director                                   August 30, 1996
- -----------------------------                                      
William F. Pounds
</TABLE> 
<PAGE>
 
                                 EXHIBIT LIST
                                 ------------


EXHIBIT NO.    DESCRIPTION OF EXHIBIT
- -----------    ----------------------

   4.1         Specimen Common Stock Certificate (filed as
               Exhibit 4.5 to the Registrant's Registration
               Statement on Form S-1, No. 33-46871 and
               incorporated herein by reference).

   4.2         Securities Purchase Agreement dated as of August 16,
               1996 by and among the Registrant and the Selling
               Shareholders.

   5.1         Opinion of Testa, Hurwitz & Thibeault, LLP.

  23.1         Consent of Coopers & Lybrand L.L.P.

  23.2         Consent of Price Waterhouse LLP.

  23.3         Consent of Testa, Hurwitz & Thibeault, LLP
               (contained in Exhibit 5.1).

  23.4         Consent of Coopers & Lybrand L.L.P. relating
               to the financial statements of the In Vitro
               Business of Advanced Magnetics, Inc.

  23.5         Consent of Coopers & Lybrand L.L.P. relating
               to the financial statements of the Biosearch
               Division of Millipore Corporation.

  23.6         Consent of Mir Fox & Rodriguez relating to
               the financial statements of Vestec
               Corporation.

  24.1         Power of Attorney (included on page II-5 of
               the Registration Statement).

<PAGE>
 
                                                                     EXHIBIT 4.2
                   SECURITIES PURCHASE AGREEMENT

   THIS AGREEMENT is by and between PERSEPTIVE BIOSYSTEMS, INC. (the "Company"),
a Delaware corporation with an office at 500 Old Connecticut Path, Framingham,
Massachusetts 01701 U.S.A., and the purchaser whose name and address is set
forth on the signature page hereto (the "Purchaser").

   IN CONSIDERATION of the mutual covenants contained in this Agreement and good
and valuable consideration, the receipt and sufficiency of which is hereby
acknowledged, the parties agree as follows:

   SECTION 1.   Authorization of Shares.  The Company has authorized the sale of
                -----------------------                                         
up to a maximum of 3,000,000,000 shares (the "Shares") of the Company's Common
Stock, $.01 par value (the "Common Stock").

   SECTION 2.   Agreement to Sell and Purchase the Shares.  At the Closing (as
                -----------------------------------------                     
defined in Section 4, the Company will sell to the Purchaser, and the
Purchaser will buy from the Company, upon the terms and conditions hereinafter
set forth, the number of Shares set forth on the signature page hereof at a
purchase price per Share of $7.00.

   The Company represents and warrants that, at the Closing or subsequent
closings, the Company may enter into substantially this same form of purchase
agreement with certain other investors (the "Other Purchasers").  The Purchaser
and the Other Purchasers are hereinafter sometimes collectively referred to as
the "Purchasers," and this Agreement and the agreements executed by the Other
Purchasers are hereinafter sometimes collectively referred to as the
"Agreements."

   SECTION 3.   Payment of Purchase Price.  On or prior to the Closing Date, as
                -------------------------                                      
defined below, the Purchaser will deliver to the Company the full amount of the
aggregate purchase price for the Shares purchased hereunder (the "Purchase
Price") by check or wire transfer of funds.

   SECTION 4.   The Closing.  The consummation of the transactions contemplated
                -----------                                                    
by this Agreement (the "Closing") shall occur on a date (the "Closing Date") not
more than thirty (30) days from the date hereof and at such place and time as
shall be specified by the Company, of which the Purchasers will be notified in
advance by Company.  At the Closing, the Company shall deliver to the Purchaser
one or more common stock certificates registered in the name of the Purchaser,
or, if so indicated on the signature page hereof, in the name of a nominee
designated by the Purchaser, representing the number of Shares to be purchased
by it.

   SECTION 5.   Representations, Warranties and Covenants of the Company. The
                --------------------------------------------------------     
Company hereby represents and warrants to, and covenants with, the Purchaser
that, except as disclosed in the Company's Confidential Private Placement
Memorandum dated August 1996, including the exhibits thereto and as supplemented
from time to time prior to the Closing (the "Memorandum"), distributed in
connection with the offer and sale of the Shares:

<PAGE>
 
   SECTION 5.1. Organization.  The Company is duly organized and validly
                ------------                                            
existing in good standing under the laws of the State of Delaware.  The
Company has full power and authority to own, operate and occupy its properties
and to conduct its business as presently conducted and is registered or
qualified to do business and in good standing in each jurisdiction in which it
owns or leases property or transacts business and where the failure to be so
qualified would have a material adverse effect upon the business, financial
condition, properties or operations of the Company.

   SECTION 5.2. Due Authorization.  The Company has all requisite power and
                -----------------                                          
authority to execute, deliver and perform its obligations under this Agreement,
and this Agreement has been duly authorized and validly executed and delivered
by the Company and constitutes legal, valid and binding agreements of the
Company enforceable against the Company in accordance with their respective
terms, except as rights to indemnity and contribution may be limited by state or
federal securities laws or the public policy underlying such laws, except as
enforceability may be limited by applicable bankruptcy, insolvency,
reorganization, moratorium or similar laws affecting creditors' and contracting
parties' rights generally and except as enforceability may be subject to general
principles of equity (regardless of whether such enforceability is considered in
a proceeding in equity or at law).

   SECTION 5.3. Non-Contravention.  The execution and delivery of this
                -----------------                                     
Agreement, the issuance and sale of the Shares to be sold by the Company
hereunder, and the consummation of the transactions contemplated hereby will not
conflict with or constitute a violation of, or default (with the passage of time
or otherwise) under, any material agreement or instrument to which the Company
is a party or by which it is bound or the Amended and Restated Certificate of
Incorporation, as amended (the "Charter") or the Amended and Restated By-
Laws, as amended, of the Company nor result in the creation or imposition
of any lien, encumbrance, claim, security interest or restriction whatsoever
upon any of the material properties or assets of the Company or an acceleration
of indebtedness pursuant to any obligation, agreement or condition contained in
any material bond, debenture, note or any other evidence of indebtedness or any
material indenture, mortgage, deed of trust or any other agreement or instrument
to which the Company is a party or by which the Company is bound or to which any
of the property or assets of the Company is subject, nor conflict with, or
result in a violation of, any law, administrative regulation, ordinance or order
of any court or governmental agency, arbitration panel or authority applicable
to the Company.  No consent, approval, authorization or other order of, or
registration, qualification or filing with, any regulatory body, administrative
agency, or other governmental body in the United States, other than with respect
to "blue sky" laws, is required for the valid issuance and sale of the Shares to
be sold pursuant to this Agreement (other than such as have been made or
obtained).

   SECTION 5.4. Capitalization.  The capitalization of the Company is as set
                --------------                                              
forth in the Memorandum as of the date indicated therein. The Company has not
issued any capital stock since that date other than shares of Common Stock
issued upon exercise of outstanding options or warrants. The Shares have been
duly authorized, and when issued and paid for in accordance with the terms of
this Agreement, will be validly issued, fully paid and nonassessable.

                                 -2-
<PAGE>
 
   SECTION 5.5. Legal Proceedings.  Except as disclosed in the Company's SEC
                -----------------                                              
Filings (as hereinafter defined), there is no material legal or governmental
proceeding pending or, to the knowledge of the Company, threatened or
contemplated to which the Company is or may be a party or of which the business
or property of the Company is or may be subject.

   SECTION 5.6. No Violations.  The Company is not in violation of its Charter
                -------------                                                 
or By-Laws, in violation of any law, administrative regulation, ordinance or
order of any court or governmental agency, arbitration panel or authority
applicable to the Company, which violation, individually or in the aggregate,
would have a material adverse effect on the business or financial condition of
the Company, or is in default in any material respect in the performance of any
obligation, agreement or condition contained in any bond, debenture, note or any
other evidence of indebtedness in any indenture, mortgage, deed of trust or any
other agreement or instrument to which the Company is a party or by which the
Company is bound or by which the properties of the Company are bound or
affected, and there exists no condition which, with the passage of time or
otherwise, would constitute a material default under any such document or
instrument or result in the imposition of any material penalty or the
acceleration of any indebtedness.

   SECTION 5.7. Governmental Permits, Etc.  The Company has all necessary
                -------------------------                                
franchises, licenses, certificates and other authorizations from any foreign,
federal, state or local government or governmental agency, department, or body
that are currently necessary for the operation of the business of the Company as
currently conducted and as described in the Memorandum, the absence of which
would have a material adverse effect on the business or operations of the
Company.

   SECTION 5.8. Financial Statements.  The financial statements of the Company
                --------------------                                          
and the related notes contained in the Company's Annual Report on Form 10-K for
the fiscal year ended September 30, 1995, as amended, and its Quarterly Reports
on Form 10-Q for quarter ended December 31, 1995, March 31, 1996 and June 30,
1996 attached as an exhibit to the Memorandum (collectively, the "SEC Filings"),
present fairly the financial position of the Company, as of the dates indicated
therein, and the results of its operations and cash flows for the periods
therein specified. Such financial statements (including the related notes) have
been prepared in accordance with generally accepted accounting principles
applied on a consistent basis throughout the periods therein specified and are
true, correct and complete in all respects.

   SECTION 5.9. No Material Adverse Change.  Subsequent to the respective dates
                --------------------------                                     
as of which information is given in the Memorandum, the Company has not incurred
any material liabilities or obligations, direct or contingent, other than in the
ordinary course of business, and there has not been any material adverse change
in its consolidated condition (in each case, financial or other), results of
operations, business, prospects, key personnel or capitalization.

   SECTION 5.10.  Placement Memorandum.  The information contained in the
                  --------------------                                   
Memorandum (including the SEC Filings incorporated therein) is true and
correct in all material respects; and the Memorandum does not contain an untrue
statement of a material fact or omit to state a material fact required to be
stated therein or necessary to make the statements therein, in light of the
circumstances under which they were made, not misleading.

                                      -3-
<PAGE>
 
   SECTION 5.11.  Additional Information.  The Company has filed in a timely
                  ----------------------                                    
manner all documents that the Company was required to file under the Securities
Exchange Act of 1934, as amended (the "Exchange Act") during the 12 months
preceding the date of this Agreement.  The following documents complied in all
material respects with the requirements of the Exchange Act as of their
respective filing dates, and the information contained therein was true and
correct in all material respects as of the date of such documents, and each of
the following documents as of the date thereof did not contain an untrue
statement of a material fact or omit to state a material fact required to be
stated therein or necessary to make the statements therein, in light of the
circumstances under which they were made, not misleading:

       (a)  The Company's Annual Report on Form 10-K for the fiscal year ended
            September 30, 1995, as amended, its Quarterly Reports on Form 10-Q
            for the three-month periods ended December 31, 1995, March 31, 1996
            and June 30, 1996 and its Proxy Statement for the Annual Meeting of
            Stockholders held on May 6, 1996; and
            
       (b)  all other documents, if any, filed by the Company with the
            Securities and Exchange Commission (the "SEC") since the filing of
            the Quarterly Report on Form 10-Q for the three-month period ended
            June 30, 1996 pursuant to the reporting requirements of the Exchange
            Act.

   SECTION 5.12.   Intellectual Property.  The Company owns all right, title and
                   ---------------------                                        
interest in and to, all of the intellectual property owned and used by it (the
"Intellectual Property") free and clear of any liens or encumbrances; in any
case in which the Company does not own such Intellectual Property, it has good
and valid licenses for the same which are in full force and effect; in either
case, the Company has the right to use all Intellectual Property as now used in
its business.  Except as disclosed in the SEC Filings, no claims have
been asserted with respect to the use of any such Intellectual Property or
challenging or questioning the validity or effectiveness of any such license or
agreement.

   SECTION 5.13.  Default on Contracts.  (a) The Company is not in violation of,
                  --------------------                                          
or (with or without notice or the passage of time or both) in default under, any
term or provision of any contract, mortgage, deed of trust, bond, indenture,
lease, license, note, franchise certificate, option, warrant, right or other
instrument, undertaking, document or written agreement and any oral obligation,
right or agreement of any kind and nature whatsoever (hereinafter collectively
referred to as "Contracts") to which the Company is a party or by or to which
the Company or its assets or properties may be bound or affected or subject,
which violation or default might reasonably be expected to have a material
adverse effect on the Company or its business, condition (financial or
otherwise), operations, assets, properties or prospects of any of them. The
Company is not aware of any fact, circumstance or event which reasonably can be
expected in the future to cause a violation or default as described in the
preceding sentence.

       (b) To the best knowledge of the Company, no party to any Contract
material to the business, condition (financial or otherwise), operations,
assets, properties or prospects of the 

                                      -4-
<PAGE>
 
Company is in violation or default thereunder, which violation or default might
reasonably be expected to have a material adverse effect on the business,
condition (financial or otherwise), operations, assets, properties or prospects
of the Company, and there exists no fact, circumstance or event, including the
transactions contemplated by this Agreement, which reasonably can be expected in
the future to cause any such party to be in any such violation or default, or
which reasonably can be expected in the future to permit any such party to
terminate any such Contract, which termination might reasonably be expected to
have a material adverse effect on the business, condition (financial or
otherwise), operations, assets, properties or prospects of the Company.

   SECTION 5.14.  Listing.  The Company shall use its best efforts to comply
                  -------                                                   
with all requirements of the National Association of Securities Dealers, Inc.
(the "NASD") and The Nasdaq Stock Market, Inc. with respect to the issuance of
the Shares and the listing of the Shares on the Nasdaq National Market.

   SECTION 6.   Representations, Warranties and Covenants of the Purchaser.
                ---------------------------------------------------------- 

          (a) The Purchaser represents and warrants to, and covenants with, the
Company, as of the date hereof and as of the Closing Date, that:  (i) the
Purchaser is an "accredited investor" as defined in the Memorandum; (ii) the
Purchaser is acquiring the number of Shares set forth below for its own account
for investment and with no present intention of distributing any of such Shares
(this representation and warranty not limiting the Purchaser's right to sell
pursuant to an effective registration statement registering the Shares for
resale or to be indemnified pursuant to the provisions hereof); (iii) the
Purchaser will not, directly or indirectly, voluntarily offer, sell, pledge,
transfer or otherwise dispose of (or solicit any offers to buy, purchase or
otherwise acquire or take a pledge of) any of the Shares, except in compliance
with the Securities Act of 1933, as amended (the "Securities Act") and the rules
and regulations promulgated thereunder; (iv) the Purchaser has had an
opportunity to ask questions and receive answers from the management of the
Company regarding the Company, its business and the offering of the Shares; (v)
the Purchaser has completed or caused to be completed the Questionnaire which is
a part hereof and the answers thereto are true and correct to the best knowledge
of the Purchaser as of the date hereof and will be true and correct as of the
effective date of the registration statement referred to in Section 9.1; (vi)
the Purchaser will notify the Company immediately of any change in any of such
information until such time as the Purchaser has sold all of its Shares or until
the Company is no longer required to keep such registration statements effective
pursuant to Sections 9.1(c); and (vii) the Purchaser has, in connection with its
decision to purchase Shares, relied solely upon the documents described in
Section 5.10 and Section 5.11 and the representations and warranties of the
Company contained herein.

          (b) The Purchaser acknowledges, represents and agrees that no action
has been or will be taken in any jurisdiction outside the United States by the
Company that would permit an offering of the Shares, or possession or
distribution of offering material in connection with the issue of the Shares, in
any country or jurisdiction outside the United States where action for that
purpose is required.  Each Purchaser outside the United States agrees to comply
with all applicable laws and regulations in each foreign jurisdiction in which
it purchases, offers, sells or

                                      -5-
<PAGE>
 
delivers Shares or has in its possession or distributes any offering material,
in all cases at its own expense.

          (c) The Purchaser agrees not to make any sale of the Shares, pursuant
to the registration statement referred to in Section 9.1 without effectively
causing the prospectus delivery requirements under the Securities Act to be
satisfied.  The Purchaser acknowledges that there may occasionally be times when
the Company must suspend the use of the prospectus forming a part of the
Registration Statement until such time as an amendment to such registration
statement has been filed by the Company and declared effective by the SEC or
until the Company has amended or supplemented such prospectus.  The Company
agrees to use its best efforts to cause such amended registration statement to
be declared effective and/or to deliver such amended or supplemented prospectus
as soon as possible.  The Purchaser hereby covenants that it will not sell any
Shares pursuant to said prospectus during the period commencing at the time at
which the Company gives the Purchaser notice of the suspension of the use of
said prospectus and ending at the time the Company gives the Purchaser notice
that the Purchaser may thereafter effect sales pursuant to said prospectus.

          (d) The Purchaser further represents and warrants to, and covenants
with, the Company that (i) the Purchaser has full right, power, authority and
capacity to enter into this Agreement and to consummate the transactions
contemplated hereby and has taken all necessary action to authorize the
execution, delivery and performance of this Agreement, and (ii) upon the
execution and delivery of this Agreement, this Agreement shall constitute a
valid and binding obligation of the Purchaser enforceable in accordance with its
terms, except as enforceability may be limited by applicable bankruptcy,
insolvency, reorganization, moratorium or similar laws affecting creditors' and
contracting parties' rights generally and except as enforceability may be
subject to general principles of equity (regardless of whether such
enforceability is considered in a proceeding in equity or at law) and except as
the indemnification agreements of the Purchaser herein may be legally
unenforceable.

   SECTION 7.   Survival of Representations, Warranties and Agreements.
                ------------------------------------------------------  
Notwithstanding any investigation made by any party to this Agreement, all
covenants, agreements, representations and warranties made by the Company and
the Purchaser herein shall survive the execution of this Agreement, the delivery
to the Purchaser of the Shares being purchased and the payment therefor.

   SECTION 8.   Conditions to Closing.
                --------------------- 

          (a) The obligations of the Purchaser to consummate the transactions
contemplated hereby shall be subject to the satisfaction by the Company of each
of the following conditions on or before the Closing Date, any one or more of
which may be waived by the Purchaser:

          (i) The representations and warranties of the Company set forth in
this Agreement delivered to the Purchaser by or on behalf of the Company shall
be true and correct as if made on the Closing Date.

                                      -6- 
<PAGE>
 
          (ii) Each of the covenants, agreements and conditions to be performed
and satisfied by the Company pursuant to this Agreement at or prior to Closing
shall have been duly performed and satisfied.

          (b) The obligations of the Company to consummate the transactions
contemplated hereby shall be subject to the satisfaction by the Purchaser of
each of the following conditions on or before the Closing Date, any one or more
of which may be waived by the Company:

          (i) The representations and warranties of the Purchaser set forth in
this Agreement shall be true and correct as if made on the Closing Date.

          (ii) Each of the covenants, agreements and conditions to be performed
and satisfied by the Purchaser pursuant to this Agreement at or prior to Closing
shall have been duly performed and satisfied.

                  (iii)  The Purchaser shall have paid the Purchase Price in
accordance with Section 3.

   SECTION 9.   Registration of the Shares; Compliance with the Securities Act.
                -------------------------------------------------------------- 

       9.1. Registration Procedures and Expenses.  The Company shall:
            ------------------------------------                     

       (a)  prepare and file with the SEC a registration statement (the
            "Registration Statement") covering the resale of the Shares by the
            Purchasers from time to time on the Nasdaq National Market, or on
            such securities market or system on which the Company's Common Stock
            shall then be publicly traded, or in privately negotiated
            transactions, no later than 60 days following the Closing Date;

       (b)  use its best efforts, subject to receipt of necessary information
            from the Purchasers, to cause the Registration Statement to become
            effective as soon as possible thereafter;

       (c)  prepare and file with the SEC such amendments and supplements to the
            Registration Statement and the prospectus used in connection
            therewith as may be necessary to comply with the provisions of the
            Securities Act until the later of such time as all of the Shares
            have been sold pursuant thereto or, by reason of Rule 144(k) under
            the Securities Act or any other rule of similar effect, such shares
            are no longer required to be registered for the unrestricted sale
            thereof by the Purchasers;

       (d)  furnish to the Purchaser such number of copies of prospectuses and
            preliminary prospectuses in conformity with the requirements of the
            Securities Act and such 

                                      -7-
<PAGE>
 
            other documents as the Purchaser may reasonably request, in order to
            facilitate the public sale or other disposition of all or any of the
            Shares held by the Purchaser, provided, however, that the obligation
            of the Company to deliver copies of prospectuses or preliminary
            prospectuses to the Purchaser shall be subject to the receipt by the
            Company of reasonable assurances from the Purchaser that the
            Purchaser will comply with the applicable provisions of the
            Securities Act and of such other securities or blue sky laws as may
            be applicable in connection with any use of such prospectuses or
            preliminary prospectuses;

       (e)  file documents required of the Company for normal blue sky clearance
            in all states, provided, however, that the Company shall not be
            required to qualify to do business or consent to service of process
            in any jurisdiction in which it is not now so qualified or has not
            so consented;

       (f)  bear all expenses in connection with the procedures in paragraphs
            (a) through (c) of this Section 9.1, other than brokerage
            commissions or placement agent fees and fees and expenses, if any,
            of counsel or other advisers to the Purchaser or the Other
            Purchasers with respect to the registration and resale of the
            Shares; and

       (g)  prepare and file additional listing applications for the Shares on
            the Nasdaq National Market. 

The Company understands that the Purchaser disclaims being an underwriter, but
the Purchaser being deemed an underwriter shall not relieve the Company of any
obligations it has hereunder.

   SECTION 9.2. Transfer of Shares After Registration.  The Purchaser agrees
                -------------------------------------                       
that it will not effect any disposition of the Shares, that would constitute a
sale within the meaning of the Securities Act except as contemplated in the
Registration Statements referred to in Section 9.1 or pursuant to an available
exemption from registration under the Securities Act and applicable state
securities laws.

   SECTION 9.3. Indemnification.  For the purpose of this Section 9.3:
                ---------------                                       

            (a) the term "Selling Shareholder" shall mean any person or entity
selling Shares pursuant to the Registration Statement, and any affiliate
thereof;

            (b) the term "Registration Statement" shall include any preliminary
prospectus, final prospectus, exhibit, supplement or amendment included in or
relating to the Registration Statement; and

            (c) the term "untrue statement" shall mean any untrue statement or
alleged untrue statement of a material fact in the Registration Statement, or
any omission or alleged omission to state in the Registration Statement a
material fact required to be stated therein or

                                      -8-
<PAGE>
 
necessary to make the statements therein, in the light of the circumstances
under which they were made, not misleading.

          The Company agrees to indemnify and hold harmless each Selling
Shareholder from and against any losses, claims, damages or liabilities to which
such Selling Shareholder may become subject (under the Securities Act or
otherwise) insofar as such losses, claims, damages or liabilities (or actions or
proceedings in respect thereof) arise out of, or are based upon, any untrue
statement, or arise out of any failure by the Company to fulfill any undertaking
included herein or in the Registration Statement, and the Company promptly will
reimburse such Selling Shareholder for any legal or other expenses reasonably
incurred in investigating, defending or preparing to defend any such action,
proceeding or claim; provided, however, that the Company shall not be liable in
any such case to the extent that such loss, claim, damage or liability arises
out of, or is based upon, an untrue statement made in reliance upon and in
conformity with written information furnished to the Company by or on behalf of
such Selling Shareholder specifically for use in preparation of the Registration
Statement, or the failure of such Selling Shareholder to comply with the
covenants and agreements contained herein; provided further, that the
indemnification contained in this Section 9.3 with respect to any prospectus
after it has been amended or supplemented, shall not inure to the benefit of any
Selling Shareholder (or any person controlling such Selling Shareholder) from
whom the person asserting such loss, claim, damage, or liability shall have
purchased Shares, that are the subject thereof if, after copies thereof have
been delivered by the Company to such Selling Shareholder, such Selling
Shareholder shall have failed to send or give a copy of the prospectus as then
amended or supplemented, as the case may be, to such person at or prior to the
confirmation of such sale of such Shares, to such person, and, if such loss,
claim, damage or liability would not have arisen but for the failure of such
Selling Shareholder to deliver the same.

       The Purchaser agrees to indemnify and hold harmless the Company (and each
other person, if any, who controls the Company within the meaning of Section 15
of the Securities Act, each officer of the Company who signs the Registration
Statement and each director of the Company) from and against any losses, claims,
damages or liabilities to which the Company (or any such officer, director or
controlling person) may become subject (under the Securities Act or otherwise),
insofar as such losses, claims, damages or liabilities (or actions or
proceedings in respect thereof) arise out of, or are based upon, any failure of
the Purchaser to comply with its covenants and agreements contained herein, or
any untrue statement if such untrue statement was made in reliance upon and in
conformity with written information furnished by or on behalf of the Purchaser
specifically for use in preparation of the Registration Statement, and the
Purchaser promptly will reimburse the Company (or such officer, director or
controlling person), as the case may be, for any legal or other expenses
reasonably incurred in investigating, defending or preparing to defend any such
action, proceeding or claim.

       Promptly after receipt by any indemnified person of a notice of a claim
or the beginning of any action in respect of which indemnity is to be sought
against an indemnifying person pursuant to this Section 9.3, such indemnified
person shall notify the indemnifying person in writing of such claim or of the
commencement of such action, and, subject to the provisions hereinafter stated,
in case any such action shall be brought against an indemnified person and

                                      -9-
<PAGE>
 
such indemnifying person shall have been notified thereof, such indemnifying
person shall be entitled to participate therein, and, to the extent it shall
wish, to assume the defense thereof, with counsel reasonably satisfactory to
such indemnified person. After notice from the indemnifying person to such
indemnified person of its election to assume the defense thereof, such
indemnifying person shall not be liable to such indemnified person for any legal
expenses subsequently incurred by such indemnified person in connection with the
defense thereof. In the event that the indemnifying party shall have assumed the
defense of such action, such indemnifying party shall not enter into any
compromise or settlement without the indemnified party's prior written consent,
which consent shall not be unreasonably withheld, delayed or denied.

   SECTION 9.4. Termination of Conditions and Obligations.  The restrictions
                -----------------------------------------                   
imposed by Section 6 or Section 9.2 upon the transferability of the Shares shall
cease and terminate as to any particular Shares when such Shares shall have been
effectively registered under the Securities Act and sold or otherwise disposed
of in accordance with the intended method of disposition set forth in the
Registration Statement or at such time as an opinion of counsel satisfactory to
the Company shall have been rendered to the effect that such restrictions are
not necessary in order to comply with the Securities Act.

   SECTION 9.5. Information Available.  So long as the Registration Statement is
                ---------------------                                           
effective covering the resale of Shares owned by the Purchaser, the Company will
furnish to the Purchaser upon request:

       (a)  any document filed by the Company with the SEC;

       (b)  upon the reasonable request of the Purchaser, any other information
            concerning the Company that is generally available to the public;
            and

       (c)  an adequate number of copies of the prospectuses relating to the
            resale of the Shares to supply to any party requiring such
            prospectuses.

   
   SECTION 10.  Notices.  All notices, requests, consents and other
                -------  
communications hereunder shall be in writing, shall be mailed by first-class
registered or certified mail, postage prepaid, and shall be deemed given when so
mailed:

            (a) if to the Company to:

                    PerSeptive Biosystems, Inc.
                    500 Old Connecticut Path
                    Framingham, MA 01701
                    Attention: Chief Executive Officer

          (b) if to the Purchaser, at its address as set forth at the end of
this Agreement, or at such other address or addresses as may have been furnished
to the Company in writing.

                                     -10-
<PAGE>
 
   SECTION 11.  Termination.
                ----------- 

          (a) By the Purchaser.  The Purchaser may terminate this Agreement
              ----------------                                             
immediately, if at any time prior to the Closing, the Company shall cease
conducting business in the normal course; become insolvent or become unable to
meet its obligations as they become due; make a general assignment for the
benefit of creditors; petition, apply for, suffer or permit with or without its
consent the appointment of custodian, receiver, trustee in bankruptcy or similar
officer for all or any substantial part of its business or assets; avail itself
or become subject to any proceeding under the Federal Bankruptcy Code or any
similar state, federal or foreign statute relating to bankruptcy, insolvency,
reorganization, receivership, arrangement, adjustment of debts, dissolutions or
liquidation.

            (b) By the Company.  The Company may terminate this Agreement at any
                --------------                                                  
time prior to the Closing.

   SECTION 12.  Changes.  Any term of the Agreements may be amended or
                -------                                               
compliance therewith waived with the written consent of the Company and the
holders of a majority of the Shares purchased pursuant to the Agreements.

   SECTION 13.  Headings.  The headings of the various sections of this
                --------                                               
Agreement have been inserted for convenience of reference only and shall not be
deemed to be part of this Agreement.

   SECTION 14.  Severability.  In case any provision 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.

   SECTION 15.  Governing Law.  This Agreement shall be governed by and
                -------------                                          
construed in accordance with the internal laws of the Commonwealth of
Massachusetts and United States federal law.

   SECTION 16.  Counterparts.  This Agreement may be executed in two or
                ------------                                           
more counterparts, each of which shall constitute an original, but all of which,
when taken together, shall constitute but one instrument, and shall become
effective when one or more counterparts have been signed by each party hereto
and delivered to the other parties.

   IN WITNESS WHEREOF, the parties hereto have caused this Stock Purchase
Agreement to be executed by their duly authorized representatives as of the
following date.

                                     -11-
<PAGE>
 
Dated: August 16, 1996 

                            PERSEPTIVE BIOSYSTEMS, INC.

                        By:
                           --------------------------------  
                           Title:

          [Purchaser Signature Page Continues on the Following Page]

                                     -12-
<PAGE>
 
                  PURCHASER SIGNATURE PAGE AND QUESTIONNAIRE
                  ------------------------------------------

   The undersigned Purchaser hereby executes the Securities Purchase Agreement
with PerSeptive Biosystems, Inc. (the "Company") and hereby authorizes this
signature page to be attached to a counterpart of such document executed by a
duly authorized officer of the Company.

No. of Shares to be                   ______________________________
Purchased:_______________             Name of Purchaser   [PLEASE
                                      PRINT OR TYPE]

Aggregate Purchase                    By:___________________________
Price  $_________________                      [SIGN HERE]
                                      Title:________________________

Purchaser is an "accredited investor" as defined in Regulation D under the
Securities Act of 1933.

Name in which Shares are to be
registered:                           ______________________________

Address of registered holder:         ______________________________

                                      ______________________________

Social Security or Tax ID Number:     ______________________________

Contact name and telephone number
regarding settlement and              ______________________________
registration:                             Name
                                      ______________________________
                                          Telephone Number

Number of shares of common stock of the Company beneficially owned (meaning
shares owned or controlled or which the Purchaser has the right to acquire or
vote) by the Purchaser, other than the Shares being purchased pursuant
hereto:____________________

Have you or your organization had any position, office or other material
relationship with the Company within the past three years?       _____ Yes
_____ No

Do you or your organization have any direct or indirect affiliation or
association with any NASD member?                _____ Yes    _____ No

If "Yes" to either of the last two questions, please indicate the nature of any
such relationships below:

                                     -13-                                      

<PAGE>
 
                                                                     Exhibit 5.1
                                                                                
                        TESTA, HURWITZ & THIBEAULT, LLP

                               ATTORNEYS AT LAW

                      HIGH STREET TOWER, 125 HIGH STREET

     OFFICE (617) 248-7000    Boston, Massachusetts  02110    FAX (617) 248-7100





                                             August 30, 1996

PerSeptive Biosystems, Inc.
500 Old Connecticut Path
Framingham, MA  01701

     RE:  Form S-3 Registration Statement
          -------------------------------

Ladies and Gentlemen:

     We are counsel to PerSeptive Biosystems, Inc., a Delaware corporation (the
"Company"), and have represented the Company in connection with the preparation
and filing of the Company's Form S-3 Registration Statement (the "Registration
Statement"), covering the sale to the public of up to 2,579,286 shares of the
Company's Common Stock, $.01 par value per share, being sold by certain
stockholders of the Company (the "Shares").  Terms not otherwise defined herein
shall have the meaning assigned to them in the Registration Statement.

     We have reviewed the corporate proceedings taken by the Board of Directors
of the Company with respect to the authorization and issuance of the Shares. We
have also examined and relied upon originals or copies, certified or otherwise
authenticated to our satisfaction, of all corporate records, documents,
agreements or other instruments of the Company and have made all investigations
of law and have discussed with the Company's officers all questions of fact that
we have deemed necessary or appropriate.

     Based upon and subject to the foregoing, we are of the opinion that the
Shares, when issued to the Selling Shareholders as described in the Registration
Statement, will be validly issued, fully paid and non-assesable.

     We hereby consent to the filing of this opinion as Exhibit 5.1 to the
Registration Statement and to the reference to our firm in the Prospectus
contained in the Registration Statement under the caption "Legal Matters."

                                         Very truly yours,


                                         /s/ Testa, Hurwitz & Thibeault, LLP


                                         TESTA, HURWITZ & THIBEAULT, LLP

<PAGE>
 
                                                                    Exhibit 23.1


                      CONSENT OF INDEPENDENT ACCOUNTANTS


     We consent to the incorporation by reference in this Registration Statement
on Form S-3 relating to the registration of Common Stock of PerSeptive 
Biosystems, Inc. held by certain selling shareholders, which shares were issued
by the Company in a Regulation D private placement on August 16, 1996, of our
reports dated November 15, 1995, on our audit of the consolidated financial
statements and financial statement schedule of PerSeptive Biosystems, Inc. We
also consent to the reference to our firm under the caption "Experts."


                                   /s/ Coopers & Lybrand L.L.P.

                                   COOPERS & LYBRAND L.L.P.


Boston, Massachusetts
August 29, 1996

<PAGE>
 
                                                                    Exhibit 23.2


                      CONSENT OF INDEPENDENT ACCOUNTANTS


     We hereby consent to the incorporation by reference in the Prospectus
constituting part of this Registration Statement on Form S-3 of our report dated
December 28, 1994, except for Note 13, as to which the date is August 11, 1995,
appearing on page F-3 of Amendment No. 1 to PerSeptive Biosystems, Inc.'s Annual
Report on Form 10-K for the year ended September 30, 1995 filed on Form 10-K/A.
We also consent to the incorporation by reference of our report on the Financial
Statement Schedule listed in Item 14(a)(2) of such Form 10-K/A. We also consent
to the reference to us under the heading "Experts" in such Prospectus.


/s/ Price Waterhouse LLP

PRICE WATERHOUSE LLP

Boston, Massachusetts
August 29, 1996

<PAGE>
 
                                                                    Exhibit 23.4


                      CONSENT OF INDEPENDENT ACCOUNTANTS


     We consent to the incorporation by reference in this Registration Statement
on Form S-3 of PerSeptive Biosystems, Inc. (the "Company")relating to the
registration of common stock of PerSeptive Biosystems, Inc. held by certain
selling shareholders, which shares were issued in a Regulation D private
placement on August 16, 1996, of our report dated October 28, 1993, which
includes an emphasis of a matter concerning certain costs and expenses presented
in the financial statements which represent allocations and management's
estimates of the costs of services provided to the In Vitro Business by Advanced
Magnetics, Inc., on our audits of the financial statements of the In Vitro
Business of Advanced Magnetics, Inc. as of September 30, 1993 and 1992 and for
the years ended September 30, 1993, 1992 and 1991 appearing in the Form 8-K/A
Amendment No. 1 to the Form 8-K, dated October 15, 1993, of PerSeptive
Biosystems, Inc. We also consent to the reference to our firm under the caption
"Experts".



                              /s/ Coopers & Lybrand L.L.P.

                              COOPERS & LYBRAND L.L.P.


Boston, Massachusetts
August 29, 1996

<PAGE>
 
                                                                    Exhibit 23.5


                      CONSENT OF INDEPENDENT ACCOUNTANTS


     We consent to the incorporation by reference in this Registration Statement
on Form S-3 of PerSeptive Biosystems, Inc. (the "Company") relating to the
registration of common stock of PerSeptive Biosystems, Inc. held by certain
selling shareholders which shares were issued by the Company in a Regulation D
private placement on August 16, 1996, of our report, which includes an
emphasis of a matter concerning certain costs and expenses presented in the
financial statements which represent allocations and management's estimates of
the costs of services provided by Millipore Corporation, dated July 22, 1994, on
our audits of the financial statements of the Biosearch Division of Millipore
Corporation as of December 31, 1992 and 1993 and the statements of operations
and cash flow for each of the three years in the period ended December 31,
1993, appearing in the Form 8-K/A Amendment No. 1 to the Form 8-K dated, August
22, 1994 of PerSeptive Biosystems, Inc. We also consent to the reference to our
firm under the caption "Experts."



                                        /s/ Coopers & Lybrand L.L.P.

                                        COOPERS & LYBRAND L.L.P.


Boston, Massachusetts
August 29, 1996

<PAGE>
 
                                                                    Exhibit 23.6


                      CONSENT OF INDEPENDENT ACCOUNTANTS


     We hereby consent to the incorporation by reference in the Prospectus
constituting part of this Registration Statement on Form S-3 of our report dated
February 12, 1993, except as to Note 11, which is as of October 8, 1993,
relating to the financial statements of Vestec Corporation appearing on page 11
of PerSeptive Biosystems, Inc.'s Amendment No. 1 to Form 8-K dated October 8,
1993 on Form 8-K/A.



/s/ Mir-Fox & Rodriguez

MIR-FOX & RODRIGUEZ

Houston, Texas
August 30, 1996


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