Document:

<PAGE>

EXHIBIT 4.5

                                IRREVOCABLE PROXY

         KNOW ALL MEN BY THESE PRESENCE THAT, the undersigned being the holders
of the common stock of Main Street IPO.com, Inc. ("Main Street"), in the amounts
appearing after their signatures as set forth below, do hereby constitute and
appoint Joseph Salvani, President of Main Street as proxy to act for each of the
undersigned and to attend all meetings of the shareholders of said Corporation
or any continuations or adjournments thereof, with full powers to vote and act
on behalf of each of the undersigned, to the same extent and with the same
effect the undersigned might, were they personally present there at, giving to
said Joseph Salvani full power of substitution and revocation

         Any proxy or proxies heretofore given by any of the undersigned to any
person or persons whatsoever are hereby revoked.

         This proxy shall remain in full force and effect for the period of two
years from the date hereof.

DATED:  New York, New York
        February 2, 2000              /S/  LAURA GEORGE
                                      -----------------------------------
                                      Laura George (600,000 shares)

                                      /S/  JOANNE BERTOLINI
                                      -----------------------------------
                                      Joanne Bertolini (1,000,000 shares)

                                      /S/  RALPH DELUCA
                                      -----------------------------------
                                      Ralph DeLuca (600,000 shares)<PAGE>

                                                                    EXHIBIT 10.1

                           CONTRIBUTION AGREEMENT dated as of October __, 1999
                           between MainStreetIPO.com, Inc., a Delaware
                           corporation (the "PURCHASER"), and the Individuals
                           listed on Schedule A hereto (the "SELLERS").

                  WHEREAS, Purchaser has entered into an Agreement and Plan of
Merger between Purchaser and Dialysis Corporation of America ("DCA"), a Florida
corporation, pursuant to which MainStreet Acquisition Corp. ("Mainstreet"), a
wholly-owned subsidiary of Purchaser, shall merge with and into DCA and the
surviving entity, shall be DCA, ("the Merger"), which shall change its name to
MainStreet;

                  WHEREAS, CEO Letter, LLC, a Delaware limited liability company
("CEO Letter"), has entered into an exclusive arrangement with FreeRide Media,
L.L.C. ("FreeRide") pursuant to which CEO Letter has the exclusive right to post
certain forms of information on a website connected by hyperlink to FreeRide's
website;

                  WHEREAS, Purchaser desires to acquire all of the outstanding
equity of CEO Letter from the Sellers, on the following terms and conditions;
and

                  WHEREAS, the Sellers desire to transfer all of the outstanding
equity of CEO Letter to Purchaser, on the following terms and conditions.

                  NOW, THEREFORE, in consideration of the premises and the
respective agreements hereinafter set forth, the parties hereto agree as
follows:

                                    ARTICLE I

                                  DEFINED TERMS

                  Section 1.01 DEFINED TERMS. The following terms, not defined
elsewhere in this Agreement, shall have the following meanings:

                  "Assets" shall mean all assets of CEO Letter including cash,
         accounts receivable, inventory, real property, equipment, supplies,
         furniture, fixtures, work-in-progress, unprocessed orders, customer
         lists, insurance policies and intellectual property rights, including,
         but not limited to, all inventions, devices, methods, processes,
         procedures, formulae, computer software, and other technology, whether
         patented, patentable or unpatentable, together with all patents,
         trademark, know-how, trade secrets, copyrights and proprietary
         information owned by or licensed by CEO Letter, including intellectual
         property rights relating to products or services of CEO Letter and CEO
         Letter's shareholders which are not commercially viable as of the
         Closing Date, goodwill, business information and any other assets,
         tangible or intangible, used or useful in the

<PAGE>

         operation of the business of CEO Letter on the Closing Date and used in
         connection with the conduct of such business.

                  "Business Day" shall mean any day other than a Saturday,
         Sunday or other day on which banks are authorized to be closed in New
         York City.

                  "Common Stock" shall mean the common stock, par value $.001,
         of Purchaser.

                  "Encumbrances" shall mean, to the extent applicable, all liens
         (including liens for taxes), mortgages, security interests, charges,
         claims, leases, survey exceptions, options, rights of first refusal or
         first offer, easements, restrictions, rights-of-way or other similar
         encumbrances of any nature whatsoever.

                  "Person" shall mean any natural person, corporation,
         association, partnership, joint venture or other entity.

                  "Units" shall mean all issued and outstanding equity interests
         of CEO Letter, LLC.

                  Section 1.02 OTHER RULES OF CONSTRUCTION. References in this
Agreement to sections, schedules and exhibits are to sections of, and schedules
and exhibits to, this Agreement unless otherwise indicated. Words in the
singular include the plural and in the plural include the singular. The word
"or" is not exclusive. The words "including", "includes", "included" and
"include", when used, are deemed to be followed by the words "without
limitation".

                                   ARTICLE II

                              TRANSFER OF INTEREST

                  Section 2.01 TRANSFER. Upon the terms and subject to the
conditions set forth in this Agreement, the Sellers agree to assign, transfer,
convey and deliver the Units to the Purchaser described in Schedule 2.01, and
the Purchaser agrees to accept the Units from the Sellers on the Closing Date.
In exchange Sellers agree to accept as consideration for the transfer of the
Units to Purchaser the Consideration on the terms set forth in Section 2.03
below.

                  Section 2.02 DELIVERY OF INSTRUMENTS OF TRANSFER. On the
Closing Date, the Sellers shall deliver to the Purchaser such specific
assignments, bills of sale, endorsements, leases and other good and sufficient
instruments of conveyance and transfer, in form and substance satisfactory to
the Purchaser, the Sellers and their respective counsel, as shall be reasonably
requested by the Purchaser to effectively vest in the Purchaser title to all the
Units.

                  Section 2.03 TRANSFER PRICE; INCENTIVE PAYMENTS. The
consideration (the "Consideration") to Sellers for the Units shall be 1,000,000
shares of Common Stock, to be paid on the following schedule:

                  (a) 250,000 shares of Common Stock on the Closing Date;

<PAGE>

                  (b) 250,000 shares upon realization of (i) $1,000,000 in sales
                      and (ii) $400,000 in pre-tax earnings during any
                      consecutive 12 month period ended on or prior to the
                      Second Anniversary of the Closing Date (determined in
                      accordance with generally accepted accounting principles
                      ("GAAP")); and

                  (c) 500,000 shares upon realization of (i) $2,000,000 in sales
                      and (ii) $800,000 in pre-tax earnings, during any
                      consecutive 12 month period ended on or prior to the
                      second anniversary of the Closing Date (determined in
                      accordance with GAAP).

                  Until the sales and earnings amounts set forth in clauses (b)
or (c) have been reached, the applicable shares of Common Stock shall be held in
escrow by Lawrence Jaffe (the "Escrowed Shares"). The shares referenced in
clauses (b) or (c) above shall be delivered to Sellers following delivery to Mr.
Jaffe of written notification that the applicable sales and earnings thresholds
have been met, together with an audited financial statement evidencing the
satisfaction of such threshold. No further evidence shall be necessary for the
release of the appropriate shares of Common Stock to Sellers. A certificate
evidencing the shares of Common Stock awarded to Sellers shall be delivered to
Sellers within ten days after receipt by Lawrence Jaffe of such notice and
evidence as set forth in the preceding sentence. In the event that the
conditions of clause (b) or (c) of this Section 2.03 are not satisfied by
Sellers prior to the Second anniversary of the Closing Date, the applicable
Escrowed Shares shall be returned to the Purchaser as treasury shares to be
retired by the Purchaser.

                  Section 2.04 THE CLOSING. The closing shall take place at
10:00 a.m. at the offices of Wollmuth Maher & Deutsch LLP on the date that the
Merger closes, or such date as may be mutually agreed by the parties (the
"CLOSING DATE"). For purposes, of this Agreement, "CLOSING" means the
consummation of the transactions contemplated by this Agreement.

                  Section 2.05 FURTHER ASSURANCES. From and after the Closing,
upon written request from the Purchaser, the Sellers shall execute, acknowledge
and deliver all such further acts, assurances, deeds, assignments, transfers,
conveyances and other instruments and papers as may be reasonably required to
sell, assign, transfer, convey and deliver the Assets to the Purchaser.

                                  ARTICLE IIII

                  REPRESENTATIONS AND WARRANTIES OF THE SELLERS

                  The Sellers represent and warrant to the Purchaser as follows:

                  Section 3.01 ORGANIZATION AND GOOD STANDING. CEO Letter is a
limited liability company duly organized, validly existing and in good standing
under the laws of the State of Delaware and has the requisite power and
authority to carry on its business as currently conducted by it and to own the
properties or Assets it now owns.

<PAGE>

                  Section 3.02 CAPITAL STRUCTURE; SUBSIDIARIES. (a) The
authorized, issued and outstanding Units of CEO Letter and a list of all holders
of issued and outstanding shares of Units (including holders of warrants,
options and similar instruments with rights to acquire shares of Units) is set
forth on Schedule 3.02. Sellers are the only holders of the issued and
outstanding Units of CEO Letter. Sellers own on the date hereof, and on the
Closing Date, the number of shares of Units set forth on Schedule 3.02, free and
clear of all Encumbrances.

                           (b) SUBSIDIARIES. There are no corporations,
partnerships or other entities in which CEO Letter owns, of record, beneficially
or otherwise, any direct or indirect equity or other interest or any right
(contingent or otherwise) to acquire the same. CEO Letter does not have any
obligation to invest in any other Person.

                  Section 3.03 AUTHORITY. The Sellers have full power and
authority to execute and deliver this Agreement and the other agreements and
instruments to be executed and delivered by the Sellers pursuant hereto and to
consummate the transactions contemplated hereby and thereby. This Agreement has
been duly executed and delivered by the Sellers and constitutes, and such other
agreements and instruments when duly executed and delivered by the Sellers will
constitute, legal, valid and binding obligations of the Sellers enforceable
against each of them in accordance with their respective terms. Except as set
forth in Schedule 3.03, the execution and delivery by the Sellers of this
Agreement and such other agreements and instruments, and the consummation by the
Sellers of the transactions contemplated hereby and thereby, will not violate
any law, or conflict with, result in any breach of, constitute a default (or an
event which with notice or lapse of time or both would become a default) under,
accelerate the performance required under, or result in the creation of a lien
or Encumbrance on the Units or the Assets pursuant to, the corporate charter or
by-laws of CEO Letter or under any indenture, mortgage, lease, agreement or
other instrument to which the Sellers or CEO Letter is a party or by which the
Sellers or CEO Letter or their respective properties or Assets are bound. No
approval, authorization, consent or other order or action of or filing with any
court, administrative agency or other governmental body in the United States of
America is required for the execution and delivery by the Sellers of this
Agreement or such other agreements and instruments, or the consummation by the
Sellers of the transactions contemplated hereby or thereby, except as set forth
in Schedule 3.03. No consent of any third party is required to consummate any of
the transactions contemplated hereby, except as set forth in Schedule 3.03.

                                   ARTICLE IV

                 REPRESENTATIONS AND WARRANTIES OF THE PURCHASER

                  The Purchaser represents and warrants to the Sellers as
follows:

                  Section 4.01 ORGANIZATION AND GOOD STANDING. The Purchaser is
a corporation duly organized, validly existing and in good standing under the
laws of the State of Delaware.

<PAGE>

                  Section 4.02 AUTHORITY. The Purchaser has the full corporate
power and authority to execute and deliver this Agreement and the other
agreements and instruments to be executed and delivered by the Purchaser,
pursuant hereto and to consummate the transactions contemplated hereby and
thereby. All Common Stock, including the Common Stock to be transferred pursuant
to this Agreement to the Sellers, has been duly authorized. All corporate acts
and other proceedings required to be taken by or on the part of the Purchaser to
authorize such execution, delivery and consummation have been duly and properly
taken, and on or before the Closing Date all corporate acts and other
proceedings required to be taken by or on the part of the Purchaser to authorize
such execution, delivery and consummation will have been properly taken. This
Agreement has been duly executed and delivered by the Purchaser and constitutes,
and such other agreements and instruments when duly executed and delivered by
the Purchaser will constitute, legal, valid and binding obligations of the
Purchaser enforceable against it in accordance with their respective terms. The
execution and delivery by the Purchaser of this Agreement and the execution and
delivery by the Purchaser of such other agreements and instruments and the
consummation by the Purchaser of the transactions contemplated hereby and
thereby will not violate any law, or conflict with, result in any breach of,
constitute a default (or an event which with notice or lapse of time or both
would become a default) under, accelerate the performance required under, or
result in the creation of a lien or Encumbrance on any of the properties or
assets of the Purchaser pursuant to, corporate charter or by-laws of the
Purchaser or any indenture, mortgage, lease, agreement or other instrument to
which the Purchaser is a party or by which the Purchaser or its properties or
assets, is bound. No approval, authorization, consent or other order or action
of or filing with any court, administrative agency or other governmental body in
the United States of America is required for the execution and delivery by the
Purchaser of this Agreement and the execution and delivery by the Purchaser of
such other agreements and instruments or the consummation by the Purchaser of
the transactions contemplated hereby or thereby, except as set forth in Schedule
4.02. No consent of any third party is required to consummate any of the
transactions contemplated hereby, except as set forth in Schedule 4.02.

                  Section 4.03 NO LEGAL PROCEEDINGS. There is no action, suit,
order, judgment or proceeding pending or, to the knowledge of the Purchaser,
threatened against or affecting the Purchaser that, individually or when
aggregated with one or more other actions, suits, orders, judgments or
proceedings, has or might reasonably be expected to have a material adverse
effect on the Purchaser's ability to perform any of its obligations hereunder or
under any of the other agreements and instruments to be executed and delivered
by the Purchaser in connection herewith.

                                    ARTICLE V

                        FURTHER COVENANTS AND AGREEMENTS

                  Section 5.01 CONDUCT OF BUSINESS OF CEO LETTER. Prior to the
Closing Date, and except as otherwise contemplated by this Agreement or with the
specific prior written consent of the Purchaser, the Sellers covenant and agree
with respect to the business of CEO Letter as follows:

<PAGE>

                  (a) Sellers shall continue to conduct the business of CEO
Letter in the ordinary course, consistent with past practices; and shall make no
dividend payments or other distributions;

                  (b) Sellers will continue to use its reasonable efforts,
consistent with past practices, to preserve the business of CEO Letter intact
and the goodwill of customers and others having business relations with CEO
Letter;

                  (c) Sellers will continue to maintain the real and personal
properties of CEO Letter in good faith in accordance with past practices;

                  (d) Sellers will not terminate or modify any leases,
contracts, governmental licenses, permits, or other authorizations or agreements
affecting the real and/or personal properties of CEO Letter's business or the
operation thereof or any additional lease or contract of any nature affecting
such properties or the operation thereof, except in the ordinary course of
business consistent with past practice;

                  (e) No debts of or claims against others held by CEO Letter
and owing in respect of the business of CEO Letter shall be canceled or released
and no such rights shall be waived or abandoned, except in the ordinary course
of business consistent with past practice; and

                  (f) Sellers will not make any change in any method of
accounting principles or practices with respect to the business of CEO Letter.

                  Sellers will promptly notify the Purchaser of any material
adverse change, after the date hereof and prior to the Closing Date, in the
business, Assets, financial condition or results of operations of the business
of CEO Letter. For purposes of this Agreement a "material adverse change" means
any change likely to cost CEO Letter greater than $20,000 in cash or revenue, or
the loss of any key employee, customer, supplier, or any loss of any
governmental approval. From the date hereof to the Closing, the Sellers will not
take any action or engage in any transaction which would render any
representation and warranty of the Sellers inaccurate in any material respect as
of the Closing Date.

                  Section 5.02 CONSENTS AND CONDITIONS TO CLOSING. From the date
hereof to and including the Closing Date, each of the parties hereto agrees (i)
to take all reasonable actions necessary to obtain (and to cooperate with each
other in obtaining) all consents, authorizations, orders, exemptions and
approvals of any third parties, including governmental bodies, required to be
obtained by it in connection with any of the transactions contemplated hereby,
(ii) to take all reasonable actions necessary to comply promptly with all legal
requirements which may be imposed on or applicable to it with respect to the
Closing and (iii) to promptly cooperate with and furnish information to each
other in connection with any such legal requirements.

                  Section 5.03 NOTIFICATION OF CERTAIN MATTERS. The Sellers
shall give prompt written notice to the Purchaser, and the Purchaser shall give
prompt written notice to the Sellers,

<PAGE>

as the case may be, of (i) the occurrence, or failure to occur, of any event
that would be likely to cause any representation or warranty by such notifying
party contained in this Agreement to be untrue or inaccurate in any material
respect at any time between or including the date of this Agreement and the
Closing Date, (ii) any knowledge of or discovery by the notifying party of the
inaccuracy of any representation or warranty by the non-notifying party
contained in this Agreement and (iii) any failure of the non-notifying party to
comply with or satisfy, in any material respect, any covenant condition or
agreement to be complied with or satisfied by it under this Agreement.

                                   ARTICLE VI

              CONDITIONS PRECEDENT TO OBLIGATIONS OF THE PURCHASER

                  All obligations of the Purchaser to effect the Closing
hereunder are, at the option of the Purchaser, subject to the conditions
precedent that, at the Closing:

                  Section 6.01 PERFORMANCE BY THE SELLERS. All the terms,
covenants, agreements and conditions of this Agreement to be complied with and
performed by the Sellers on or before the Closing shall have been complied with
and performed in all material respects.

                  Section 6.02 REPRESENTATIONS AND WARRANTIES. The
representations and warranties made by the Sellers in this Agreement shall have
been true and correct in all material respects at the date hereof and as of the
Closing with the same force and effect as though all such representations and
warranties had been made as of the Closing.

                                   ARTICLE VII

               CONDITIONS PRECEDENT TO OBLIGATIONS OF THE SELLERS

                  All obligations of the Sellers to effect the Closing hereunder
are, at the option of the Sellers, subject to the conditions precedent that, at
the Closing:

                  Section 7.01 PERFORMANCE BY THE PURCHASER. All the terms,
covenants, agreements and conditions of this Agreement to be complied with and
performed by the Purchaser on or before the Closing shall have been complied
with and performed in all material respects.

                  Section 7.02 REPRESENTATIONS AND WARRANTIES. The
representations and warranties made by the Purchaser in this Agreement shall
have been true and correct in all material respects at the date hereof and as of
the Closing with the same force and effect as though all such representations
and warranties had been made as of the Closing.

                                  ARTICLE VIII

                                  MISCELLANEOUS

<PAGE>

                  Section 8.01 NOTICES. Any notice, request or other document to
be given hereunder to a party hereto shall be effective when received and shall
be given in writing and delivered in person or sent by overnight courier,
registered or certified mail, postage prepaid, or by telecopy (receipt
confirmed) as follows:

                  IF TO THE PURCHASER:
                  MainStreetIPO.com, Inc.
                  c/o Salvani Investments, Inc.
                  Commerce Center
                  US Highway One, Suite 251
                  North Brunswick, New Jersey  08902
                  Tel:     (718) 227-6789
                  Fax:     (718) 227-6780

                  WITH A COPY TO:

                  Wollmuth Maher & Deutsch LLP
                  500 Fifth Avenue, Suite 1200
                  New York, New York 10110
                  Tel:     (212) 382-3300
                  Fax:     (212) 382-0050
                  Attention:   David H. Wollmuth, Esq.
                               Rory Deutsch, Esq.
                               Conrad Rubin, Esq.

                  AND

                  IF TO THE SELLERS PRIOR TO THE CLOSING:
                  c/o Salvani Investments, Inc.
                  Commerce Center
                  US Highway One, Suite 251
                  North Brunswick, New Jersey  08902
                  Tel:     (718) 227-6789
                  Fax:     (718) 227-6780

                  WITH A COPY TO:

                  Wollmuth Maher & Deutsch LLP
                  500 Fifth Avenue, Suite 1200
                  New York, New York 10110
                  Tel:     (212) 382-3300
                  Fax:     (212) 382-0050
                  Attention:   David H. Wollmuth, Esq.
                               Rory Deutsch, Esq.
                               Conrad Rubin, Esq.

<PAGE>

Any party hereto may change its address for receiving notices, requests and
other documents by giving written notice of such change to the other parties
hereto.

                  Section 8.02 GOVERNING LAW; CHOICE OF FORUM. This Agreement
shall be governed by and construed in accordance with the laws of the State of
New York (without regard to conflict of laws doctrines). The parties agree that
the exclusive place of jurisdiction for any action, suit or proceeding relating
to this Agreement shall be in the courts of the United States of America sitting
in the Borough of Manhattan in the City of New York or, if such courts shall not
have jurisdiction over the subject matter thereof, in the courts of the State of
New York sitting therein, and each such party hereby irrevocably and
unconditionally agrees to submit to the jurisdiction of such courts for purposes
of any such action, suit or proceeding. If such state court also does not have
jurisdiction over the subject matter thereof, then such an action, suit or
proceeding may be brought in the federal or state courts located in the states
of the principal place of business of any party hereto. Each party irrevocably
waives any objection it may have to the venue of any action, suit or proceeding
brought in such courts or to the convenience of the forum. Final judgment in any
such action, suit or proceeding shall be conclusive and may be enforced in other
jurisdictions by suit on the judgment, a certified or true copy of which shall
be conclusive evidence of the fact and the amount of any indebtedness or
liability of any party therein described.

                  Section 8.03 PARTIAL INVALIDITY. In the event that any
provision of this Agreement shall be held invalid or unenforceable by any court
of competent jurisdiction, such holding shall not invalidate or render
unenforceable any other provision hereof.

                  Section 8.04 SECTION HEADINGS. The section headings and table
of contents contained in this Agreement are for reference purposes only and
shall not affect in any way the meaning or interpretation of this Agreement.

                  Section 8.05 COUNTERPARTS. This Agreement may be executed in
two or more counterparts, each of which shall be deemed to be an original, but
both of which together shall constitute one and the same instrument.

                  Section 8.06 ENTIRE AGREEMENT. This Agreement, together with
the schedules and exhibits and the agreements, certificates and instruments
delivered pursuant hereto, contain the entire agreement among the parties
hereto, and supersede all prior agreements and undertakings (written and oral)
between the parties hereto, relating to the subject matter hereof.

<PAGE>

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

                               MAINSTREETIPO.COM, INC.,
                               AS THE PURCHASER

                               By:
                                   ---------------------------------
                               Name: Joseph Salvani
                               Title:  President

                               Sellers

                               ---------------------------------
                                         Joseph Salvani

                               ---------------------------------

                               ---------------------------------

                               ---------------------------------

                               ---------------------------------

<PAGE>

                            DISCLOSURE SCHEDULES TO
                            CONTRIBUTION AGREEMENT
                        BETWEEN MAINSTREETIPO.COM, INC.
                   AND THE SELLERS DATED AS OF OCTOBER __, 1999

<TABLE>
<CAPTION>

Disclosure Schedule:

<S>               <C>
Schedule 2.01     1,000,000 of Common Equity Units of CEO Letter, LLC

Schedule 3.02     See Schedule A.

Schedule 3.03     None.

Schedule 4.02     None.
</TABLE>

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