Exhibit 4.2


                                                          SERVICING NO.: 3404536
                                                  MERS MIN: 8000101-0000004616-8
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                  FSP 50 SOUTH TENTH STREET CORP., as mortgagor
                                                             (Borrower)

                                       to

          MORTGAGE ELECTRONIC REGISTRATION SYSTEMS, INC., as mortgagee
                                                             (Mortgagee)

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

                    MORTGAGE, ASSIGNMENT OF LEASES AND RENTS,
                      SECURITY AGREEMENT AND FIXTURE FILING

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

                         DATED:                As of December 21, 2006

                         LOCATION:             50 South Tenth Street

                                               Minneapolis, Minnesota

                         COUNTY:               Hennepin

                         MERS MIN:             8000101-0000004616-8

                         PREPARED BY AND UPON
                         RECORDATION RETURN TO:

                         Alston & Bird LLP
                         90 Park Avenue
                         New York, New York  10016
                         ATTENTION:            BOA - NYC Document Manager
                         FILE NO.:             320799
================================================================================

NOTWITHSTANDING ANYTHING TO THE CONTRARY HEREIN, ENFORCEMENT OF THIS MORTGAGE,
ASSIGNMENT OF LEASES AND RENTS, SECURITY AGREEMENT, AND FIXTURE FILING IS
LIMITED TO A DEBT AMOUNT OF $76,200,000.00 UNDER CHAPTER 287 OF MINNESOTA
STATUTES.

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<PAGE>

      THIS MORTGAGE, ASSIGNMENT OF LEASES AND RENTS, AND SECURITY AGREEMENT
(this "Security Instrument") is made as of this 21 day of December, 2006, by
FSP 50 SOUTH TENTH STREET CORP., a Delaware corporation, having its principal
place of business at 401 Edgewater Place, Suite 200, Wakefield, Massachusetts
01880-6210 as mortgagor ("Borrower") and FSP 50 SOUTH TENTH STREET LLC, a
Delaware limited liability company, having its principal place of business at
401 Edgewater Place, Suite 200, Wakefield, Massachusetts 01880-6210 ("FSP LLC"),
to MORTGAGE ELECTRONIC REGISTRATION SYSTEMS, INC. , a Delaware stock corporation
("Mortgagee"). All capitalized terms not defined herein shall have the
respective meanings set forth in the Loan Agreement (defined below).

                                    RECITALS:

      This Security Instrument is given to Mortgagee, in its capacity as nominee
for Lender (defined below) in accordance with Section 16.2 below, to secure a
loan (the "Loan") in the principal sum of Seventy-Six Million Two Hundred
Thousand and No/100 Dollars ($76,200,000) advanced pursuant to that certain Loan
Agreement, dated as of the date hereof, between Borrower and Bank of America,
N.A. ("Lender"), among others (as the same may be amended, restated, replaced,
supplemented or otherwise modified from time to time, the "Loan Agreement") and
evidenced by that certain Promissory Note, dated as of the date hereof, made by
Borrower in favor of Lender (such Promissory Note, together with all extensions,
renewals, replacements, restatements or modifications thereof, being hereinafter
referred to as the "Note");

      Borrower desires to secure the payment of the Debt (as defined in the Loan
Agreement) and the performance of all of its obligations under the Note, the
Loan Agreement and the other Loan Documents (as defined in the Loan Agreement);
and

      This Security Instrument is given pursuant to the Loan Agreement, and
payment, fulfillment, and performance by Borrower of its obligations thereunder
and under the other Loan Documents are secured hereby.

                         Article 1 - GRANTS OF SECURITY

      Section 1.1 PROPERTY MORTGAGED. Borrower and, with respect to Section
1.1(f) below, FSP LLC, does hereby irrevocably mortgage, grant, bargain, sell,
pledge, assign, warrant, transfer, convey and grant a security interest to
Mortgagee and its successors and assigns the following property, rights,
interests and estates now owned, or hereafter acquired by Borrower or FSP LLC
(collectively, the "Property"):

      (a) Land. The real property described in Exhibit A attached hereto and
made a part hereof (the "Land");

      (b) Additional Land. All additional lands, estates and development rights
hereafter acquired by Borrower for use in connection with the Land and the
development of the Land and all additional lands and estates therein which may,
from time to time, by supplemental mortgage or otherwise be expressly made
subject to the lien of this Security Instrument;


<PAGE>

      (c) Improvements. The buildings, structures, fixtures, pads, additions,
enlargements, extensions, modifications, repairs, replacements and improvements
now or hereafter erected or located on the Land (collectively, the
"Improvements");

      (d) Easements. All easements, rights-of-way or use, rights, strips and
gores of land, streets, ways, alleys, passages, sewer rights, water, water
courses, water rights and powers, air rights and development rights, and all
estates, rights, titles, interests, privileges, liberties, servitudes,
tenements, hereditaments and appurtenances of any nature whatsoever, in any way
now or hereafter belonging, relating or pertaining to the Land and the
Improvements and the reversions and remainders, and all land lying in the bed of
any street, road or avenue, opened or proposed, in front of or adjoining the
Land, to the center line thereof and all the estates, rights, titles, interests,
rights of dower, rights of curtesy, property, possession, claim and demand
whatsoever, both at law and in equity, of Borrower of, in and to the Land and
the Improvements and every part and parcel thereof, with the appurtenances
thereto;

      (e) Fixtures and Personal Property. All machinery, equipment, fixtures
(including, but not limited to, all heating, air conditioning, plumbing,
lighting, communications and elevator fixtures), furniture, software used in or
to operate any of the foregoing and other property of every kind and nature
whatsoever owned by Borrower, or in which Borrower has or shall have an
interest, now or hereafter located upon the Land and the Improvements, or
appurtenant thereto, and usable in connection with the present or future
operation and occupancy of the Land and the Improvements and all building
equipment, materials and supplies of any nature whatsoever owned by Borrower, or
in which Borrower has or shall have an interest, now or hereafter located upon
the Land and the Improvements, or appurtenant thereto, or usable in connection
with the present or future operation and occupancy of the Land and the
Improvements (collectively, the "Personal Property"), and the right, title and
interest of Borrower in and to any of the Personal Property which may be subject
to any security interests, as defined in the Uniform Commercial Code, as adopted
and enacted by the state or states where any of the Property is located (the
"Uniform Commercial Code"), and all proceeds and products of the above;

      (f) Leases and Rents. All leases, master leases, subleases, subsubleases,
lettings, licenses, concessions or other agreements (whether written or oral)
pursuant to which any Person is granted a possessory interest in, or right to
use or occupy all or any portion of, the Land and the Improvements, and every
modification, amendment or other agreement relating to such leases, subleases,
subsubleases, or other agreements entered into in connection with such leases,
subleases, subsubleases, or other agreements and every guarantee of the
performance and observance of the covenants, conditions and agreements to be
performed and observed by the other party thereto, heretofore or hereafter
entered into, whether before or after the filing by or against Borrower of any
petition for relief under any Creditors Rights Laws (collectively, the "Leases")
and all right, title and interest of Borrower, its successors and assigns
therein and thereunder, including, without limitation, cash or securities
deposited thereunder to secure the performance by the lessees of their
obligations thereunder and all rents, additional rents, rent equivalents, moneys
payable as damages or in lieu of rent or rent equivalents, royalties (including,
without limitation, all oil and gas or other mineral royalties and bonuses),
income, receivables, receipts, revenues, deposits (including, without
limitation, security, utility and other deposits), accounts, cash, issues,
profits, charges for services rendered, and other consideration of whatever form


                                       -2-
<PAGE>

or nature received by or paid to or for the account of or benefit of Borrower or
its agents or employees from any and all sources arising from or attributable to
the Property, including, all receivables, customer obligations, installment
payment obligations and other obligations now existing or hereafter arising or
created out of the sale, lease, sublease, license, concession or other grant of
the right of the use and occupancy of property or rendering of services by
Borrower or Manager and proceeds, if any, from business interruption or other
loss of income insurance whether paid or accruing before or after the filing by
or against Borrower of any petition for relief under any Creditors Rights Laws
(collectively, the "Rents") and all proceeds from the sale or other disposition
of the Leases and the right to receive and apply the Rents to the payment of the
Debt;

      (g) Insurance Proceeds. All Insurance Proceeds in respect of the Property
under any Policies covering the Property, including, without limitation, the
right to receive and apply the proceeds of any insurance, judgments, or
settlements made in lieu thereof, for damage to the Property;

      (h) Condemnation Awards. All Awards, including interest thereon, which may
heretofore and hereafter be made with respect to the Property by reason of
Condemnation, whether from the exercise of the right of eminent domain
(including, but not limited to, any transfer made in lieu of or in anticipation
of the exercise of the right), or for a change of grade, or for any other injury
to or decrease in the value of the Property;

      (i) Tax Certiorari. All refunds, rebates or credits in connection with
reduction in real estate taxes and assessments charged against the Property as a
result of tax certiorari or any applications or proceedings for reduction;

      (j) Rights. The right, in the name and on behalf of Borrower, to appear in
and defend any material action or material proceeding brought with respect to
the Property to protect the interest of Lender in the Property and to commence
any material action or material proceeding to protect the interest of Lender in
the Property;

      (k) Agreements. All agreements, contracts, certificates, instruments,
franchises, permits, licenses, plans, specifications and other documents, now or
hereafter entered into, and all rights therein and thereto, respecting or
pertaining to the use, occupation, construction, management or operation of the
Land and any part thereof and any Improvements or any business or activity
conducted on the Land and any part thereof and all right, title and interest of
Borrower therein and thereunder, including, without limitation, the right, upon
the happening of any default hereunder, to receive and collect any sums payable
to Borrower thereunder, and ;

      (l) Intangibles. Except with respect to any references to "FSP" or
"Franklin Street", all tradenames, trademarks, servicemarks, logos, copyrights,
goodwill, books and records and all other general intangibles relating to or
used in connection with the operation of the Property;

      (m) Accounts. All reserves, escrows and deposit accounts maintained by
Borrower with respect to the Property, including, without limitation, the
Reserve Accounts, the Lockbox Account, the Cash Management Account and all
accounts established pursuant to Article 10 of the Loan Agreement together with
all deposits or wire transfers made to the Lockbox Account and all cash, checks,
drafts, certificates, securities, investment property, financial assets,
instruments and other property held therein from time to time and all proceeds,
products, distributions or dividends or substitutions thereon and thereof;


                                       -3-
<PAGE>

      (n) Conversion. All proceeds of the conversion, voluntary or involuntary,
of any of the foregoing items set forth in subsections (a) through (m)
including, without limitation, Insurance Proceeds and Awards, into cash or
liquidation claims

      (o) Membership Interests; all of the limited liability company membership
interests of Borrower in FSP LLC, together with all limited liability company
membership certificates, options or rights of any nature whatsoever which may be
issued or granted by FSP LLC to Borrower, together with all securities, moneys
or property representing dividends or interest on any of the membership
interests, or representing a distribution in respect of the membership
interests, or resulting from a split-up, revision, reclassification or other
like change of the membership interests or otherwise received in exchange
therefor, and any subscription warrants, rights or options issued to the holders
of, or otherwise in respect of, the membership interests, and all of Borrower's
claims, rights, powers, privileges, authority, options, security interests,
Liens and remedies, if any, under or arising out of the ownership of such
membership interests; and

      (p) Other Rights. Any and all other rights of Borrower in and to the items
set forth in subsections (a) through (o) above.

      Section 1.2 ASSIGNMENT OF RENTS. Borrower hereby absolutely and
unconditionally assigns to Mortgagee all of Borrower's right, title and interest
in and to all current and future Leases and Rents; it being intended by Borrower
that this assignment constitutes a present, absolute assignment and not an
assignment for additional security only. Nevertheless, subject to the terms of
the Loan Agreement and Section 8.1(h) of this Security Instrument, Mortgagee
grants to Borrower a revocable license to collect, receive, use and enjoy the
Rents and Borrower shall hold the Rents, or a portion thereof sufficient to
discharge all current sums due on the Debt, for use in the payment of such sums.

      Section 1.3 SECURITY AGREEMENT. This Security Instrument is both a real
property mortgage and a "security agreement" within the meaning of the Uniform
Commercial Code. The Property includes both real and personal property and all
other rights and interests, whether tangible or intangible in nature, of
Borrower in the Property. By executing and delivering this Security Instrument,
Borrower hereby grants to Mortgagee, as security for the Obligations
(hereinafter defined), a security interest in the Personal Property to the full
extent that the Personal Property may be subject to the Uniform Commercial Code.

      Section 1.4 FIXTURE FILING. Certain of the Property is or will become
"fixtures" (as that term is defined in the Uniform Commercial Code) on the Land,
and this Security Instrument, upon being filed for record in the real estate
records of the city or county wherein such fixtures are situated, shall operate
also as a financing statement filed as a fixture filing in accordance with the
applicable provisions of said Uniform Commercial Code upon such of the Property
that is or may become fixtures.


                                       -4-
<PAGE>

      Section 1.5 CONDITIONS TO GRANT. TO HAVE AND TO HOLD the above granted and
described Property unto and to the use and benefit of Mortgagee and its
successors and assigns, forever; PROVIDED, HOWEVER, these presents are upon the
express condition that, if Borrower shall well and truly pay to Lender the Debt
at the time and in the manner provided in the Note, the Loan Agreement and this
Security Instrument, shall well and truly perform the Other Obligations as set
forth in this Security Instrument and shall well and truly abide by and comply
with each and every covenant and condition set forth herein and in the Note, the
Loan Agreement and the other Loan Documents, these presents and the estate
hereby granted shall cease, terminate and be void; provided, however, that
Borrower's obligation to indemnify and hold harmless Lender pursuant to the
provisions hereof shall survive any such payment or release.

      Section 1.6 GRANTS TO MORTGAGEE. This Security Instrument and the grants,
assignments and transfers made to Mortgagee in this Article 1 shall inure to
Mortgagee solely in its capacity as Lender's nominee in accordance with Section
16.2 below.

                    Article 2 - DEBT AND OBLIGATIONS SECURED

      Section 2.1 DEBT. This Security Instrument and the grants, assignments and
transfers made in Article 1 are given for the purpose of securing the Debt.

      Section 2.2 OTHER OBLIGATIONS. This Security Instrument and the grants,
assignments and transfers made in Article 1 are also given for the purpose of
securing the performance of the following (the "Other Obligations"): (a) all
other obligations of Borrower contained herein; (b) each obligation of Borrower
contained in the Loan Agreement and any other Loan Document; and (c) each
obligation of Borrower contained in any renewal, extension, amendment,
modification, consolidation, change of, or substitution or replacement for, all
or any part of the Note, the Loan Agreement or any other Loan Document.

      Section 2.3 DEBT AND OTHER OBLIGATIONS. Borrower's obligations for the
payment of the Debt and the performance of the Other Obligations shall be
referred to collectively herein as the "Obligations."

      Section 2.4 PAYMENT OF DEBT. Borrower will pay the Debt at the time and in
the manner provided in the Loan Agreement, the Note and this Security
Instrument.

      Section 2.5 INCORPORATION BY REFERENCE. All the covenants, conditions and
agreements contained in (a) the Loan Agreement, (b) the Note and (c) all and any
of the other Loan Documents, are hereby made a part of this Security Instrument
to the same extent and with the same force as if fully set forth herein.

                         Article 3 - PROPERTY COVENANTS

      Borrower covenants and agrees that:

      Section 3.1 INSURANCE. Borrower shall obtain and maintain, or cause to be
maintained, in full force and effect at all times insurance with respect to
Borrower and the Property as required pursuant to the Loan Agreement.


                                       -5-
<PAGE>

Section 3.2 TAXES. Borrower shall pay all Taxes and Other Charges assessed or
imposed against the Property or any part thereof in accordance with the Loan
Agreement.

      Section 3.3 LEASES. Borrower shall not enter into any Leases for all or
any portion of the Property unless in accordance with the provisions of the Loan
Agreement.

      Section 3.4 WARRANTY OF TITLE. Borrower has good, indefeasible, marketable
and insurable fee simple title to the real property comprising part of the
Property and good indefeasible and marketable title to the balance of the
Property, free and clear of all Liens whatsoever except the Permitted
Encumbrances, such other Liens as are permitted pursuant to the Loan Documents
and the Liens created by the Loan Documents. This Security Instrument, when
properly recorded in the appropriate records, together with any Uniform
Commercial Code financing statements required to be filed in connection
therewith, will create (a) a valid, perfected first priority lien on the
Property, subject only to Permitted Encumbrances and the Liens created by the
Loan Documents and (b) perfected security interests in and to, and perfected
collateral assignments of, all personalty (including the Leases), all in
accordance with the terms thereof, in each case subject only to any applicable
Permitted Encumbrances, such other Liens as are permitted pursuant to the Loan
Documents and the Liens created by the Loan Documents. Borrower shall forever
warrant, defend and preserve the title and the validity and priority of the Lien
of this Security Instrument and shall forever warrant and defend the same to
Lender against the claims of all Persons whomsoever.

      Section 3.5 PAYMENT FOR LABOR AND MATERIALS. Borrower will promptly pay
when due all bills and costs for labor, materials, and specifically fabricated
materials incurred in connection with the Property and never permit to exist
beyond the due date thereof in respect of the Property or any part thereof any
Lien or security interest, even though inferior to the Liens and the security
interests hereof, and in any event never permit to be created or exist in
respect of the Property or any part thereof any other or additional Lien or
security interest other than the Liens or security interests hereof except for
the Permitted Encumbrances. Borrower represents that it has no knowledge of any
claims for payment for work, labor or materials affecting the Property which are
or may become a lien prior to, or of equal priority with, the Liens created by
the Loan Documents.

                         Article 4 - FURTHER ASSURANCES

      Section 4.1 COMPLIANCE WITH LOAN AGREEMENT. Borrower shall comply with the
covenants set forth in Article 17 of the Loan Agreement in order to protect and
perfect the Lien or security interest hereof upon, and in the interest of Lender
in, the Property.

      Section 4.2 AUTHORIZATION TO FILE FINANCING STATEMENTS; POWER OF ATTORNEY.
Borrower hereby authorizes Lender at any time and from time to time to file any
initial financing statements, amendments thereto and continuation statements as
authorized by applicable law, as applicable to all or part of the Personal
Property. For purposes of such filings, Borrower agrees to furnish any
information requested by Lender promptly upon request by Lender. Borrower also
ratifies its authorization for Lender to have filed any like initial financing
statements, amendments thereto or continuation statements, if filed prior to the
date of this Security Instrument. Borrower hereby irrevocably constitutes and
appoints Lender and any officer or agent of Lender, with full power of


                                       -6-
<PAGE>

substitution, as its true and lawful attorneys-in-fact with full irrevocable
power and authority in the place and stead of Borrower or in Borrower's own name
to execute in Borrower's name any such documents and otherwise to carry out the
purposes of this Section 4.2, to the extent that Borrower's authorization above
is not sufficient. To the extent permitted by law, Borrower hereby ratifies all
acts said attorneys-in-fact have lawfully done in the past or shall lawfully do
or cause to be done in the future by virtue of this Section 4.2. This power of
attorney is a power coupled with an interest and shall be irrevocable.

                       Article 5 - DUE ON SALE/ENCUMBRANCE

      Section 5.1 NO SALE/ENCUMBRANCE. Borrower shall not cause or permit a
sale, conveyance, mortgage, grant, bargain, encumbrance, pledge, assignment,
grant of any options with respect to, or any other transfer or disposition
(directly or indirectly, voluntarily or involuntarily, by operation of law or
otherwise, and whether or not for consideration or of record) of a legal or
beneficial interest in the Property or any part thereof, Borrower or any
Restricted Party, other than in accordance with the provisions of Article 7 of
the Loan Agreement, without the prior written consent of Lender.

                   Article 6 - PREPAYMENT; RELEASE OF PROPERTY

      Section 6.1 PREPAYMENT. The Debt may not be prepaid in whole or in part
except in strict accordance with the express terms and conditions of the Note
and the Loan Agreement.

      Section 6.2 PREPAYMENT ON CASUALTY/CONDEMNATION AND CHANGE IN TAX AND
DEBIT CREDIT LAWS. Provided no Event of Default exists under any of the Loan
Documents, in the event of any prepayment of the Debt pursuant to the terms of
Article 8 or Section 17.4 of the Loan Agreement, no prepayment premium shall be
due in connection therewith, but Borrower shall be responsible for all other
amounts due under any of the Loan Documents.

      Section 6.3 INVOLUNTARY PREPAYMENT. If there is an involuntary prepayment
during the Lockout Period (as defined in the Loan Agreement) or a Default
Prepayment after the expiration of the Lockout Period, then Borrower shall, in
addition to any portion of the Loan prepaid (together with all interest accrued
and unpaid thereon), pay to Lender the applicable prepayment premium in an
amount calculated in accordance with Article 2 of the Loan Agreement.

      Section 6.4 RELEASE OF PROPERTY. Borrower shall not be entitled to a
release of any portion of the Property from the lien of this Security Instrument
except in accordance with terms and conditions of the Loan Agreement.

                               Article 7 - DEFAULT

      Section 7.1 EVENT OF DEFAULT. The term "Event of Default" as used in this
Security Instrument shall have the meaning assigned to such term in the Loan
Agreement.


                                       -7-
<PAGE>

                  Article 8 - RIGHTS AND REMEDIES UPON DEFAULT

      Section 8.1 REMEDIES. Upon the occurrence and during the continuance of
any Event of Default, Borrower agrees that Lender may take such action, without
notice or demand, as it deems advisable to protect and enforce its rights
against Borrower and in and to the Property, including, but not limited to, the
following actions, each of which may be pursued concurrently or otherwise, at
such time and in such order as Lender may determine, in its sole discretion,
without impairing or otherwise affecting the other rights and remedies of
Lender:

      (a) declare the entire unpaid Debt to be immediately due and payable;

      (b) institute proceedings, judicial or otherwise, for the complete
foreclosure of this Security Instrument under any applicable provision of law,
in which case the Property or any interest therein may be sold for cash or upon
credit in one or more parcels or in several interests or portions and in any
order or manner;

      (c) with or without entry, to the extent permitted and pursuant to the
procedures provided by applicable law, institute proceedings for the partial
foreclosure of this Security Instrument for the portion of the Debt then due and
payable, subject to the continuing lien and security interest of this Security
Instrument for the balance of the Debt not then due, unimpaired and without loss
of priority;

      (d) sell for cash or upon credit the Property or any part thereof and all
estate, claim, demand, right, title and interest of Borrower therein and rights
of redemption thereof, pursuant to power of sale or otherwise, at one or more
sales, as an entirety or in parcels, at such time and place, upon such terms and
after such notice thereof as may be required or permitted by law;

      (e) institute an action, suit or proceeding in equity for the specific
performance of any covenant, condition or agreement contained herein, in the
Note, the Loan Agreement or in the other Loan Documents;

      (f) recover judgment on the Note either before, during or after any
proceedings for the enforcement of this Security Instrument or the other Loan
Documents;

      (g) apply for the appointment of a receiver, trustee, liquidator or
conservator of the Property, without notice and without regard for the adequacy
of the security for the Debt and without regard for the solvency of Borrower,
Borrower Principal or any other Person liable for the payment of the Debt;

      (h) revoke the license granted to Borrower under Section 1.2 hereof and
Lender may enter into or upon the Property, either personally or by its agents,
nominees or attorneys and dispossess Borrower and its agents and servants
therefrom, without liability for trespass, damages or otherwise and exclude
Borrower and its agents or servants wholly therefrom, and take possession of all
books, records and accounts relating thereto and Borrower agrees to surrender
possession of the Property and of such books, records and accounts to Lender
upon demand, and thereupon Lender may (i) use, operate, manage, control, insure,
maintain, repair, restore and otherwise deal with all and every part of the
Property and conduct the business thereat; (ii) complete any construction on the
Property in such manner and form as Lender deems advisable; (iii) make


                                       -8-
<PAGE>

alterations, additions, renewals, replacements and improvements to or on the
Property; (iv) exercise all rights and powers of Borrower with respect to the
Property, whether in the name of Borrower or otherwise, including, without
limitation, the right to make, cancel, enforce or modify Leases, obtain and
evict tenants, and demand, sue for, collect and receive all Rents of the
Property and every part thereof; (v) require Borrower to pay monthly in advance
to Lender, or any receiver appointed to collect the Rents, the fair and
reasonable rental value for the use and occupation of such part of the Property
as may be occupied by Borrower; (vi) require Borrower to vacate and surrender
possession of the Property to Lender or to such receiver and, in default
thereof, Borrower may be evicted by summary proceedings or otherwise; and (vii)
apply the receipts from the Property to the payment of the Debt, in such order,
priority and proportions as Lender shall deem appropriate in its sole discretion
after deducting therefrom all expenses (including reasonable attorneys' fees)
incurred in connection with the aforesaid operations and all amounts necessary
to pay the Taxes, Other Charges, insurance and other expenses in connection with
the Property, as well as just and reasonable compensation for the services of
Lender, its counsel, agents and employees;

      (i) exercise any and all rights and remedies granted to a secured party
upon default under the Uniform Commercial Code, including, without limiting the
generality of the foregoing: (i) the right to take possession of the Personal
Property or any part thereof, and to take such other measures as Lender may deem
necessary for the care, protection and preservation of the Personal Property,
and (ii) request Borrower at its expense to assemble the Personal Property and
make it available to Lender at a convenient place acceptable to Lender. Any
notice of sale, disposition or other intended action by Lender with respect to
the Personal Property sent to Borrower in accordance with the provisions hereof
at least five (5) days prior to such action shall constitute commercially
reasonable notice to Borrower;

      (j) apply any sums then deposited or held in escrow or otherwise by or on
behalf of Lender in accordance with the terms of the Loan Agreement, this
Security Instrument or any other Loan Document to the payment of the following
items in any order in its uncontrolled discretion: (i) Taxes and Other Charges;
(ii) Insurance Premiums; (iii) interest on the unpaid principal balance of the
Note; (iv) amortization of the unpaid principal balance of the Note; (v) all
other sums payable pursuant to the Note, the Loan Agreement, this Security
Instrument and the other Loan Documents, including, without limitation, advances
made by Lender pursuant to the terms of this Security Instrument;

      (k) surrender the Policies maintained pursuant to the Loan Agreement,
collect the unearned insurance premiums for the Policies and apply such sums as
a credit on the Debt in such priority and proportion as Lender in its discretion
shall deem proper, and in connection therewith, Borrower hereby appoints Lender
as agent and attorney-in-fact (which is coupled with an interest and is
therefore irrevocable) for Borrower to collect such insurance premiums;

      (l) apply the undisbursed balance of any Net Proceeds Deficiency deposit,
together with interest thereon, to the payment of the Debt in such order,
priority and proportions as Lender shall deem to be appropriate in its
discretion; or

      (m) pursue such other remedies as Lender may have under applicable law.


                                       -9-
<PAGE>

In the event of a sale, by foreclosure, power of sale or otherwise, of less than
all of Property, this Security Instrument shall continue as a lien and security
interest on the remaining portion of the Property unimpaired and without loss of
priority. Notwithstanding the provisions of this Section to the contrary, if any
Event of Default as described in Section 11.1(f) of the Loan Agreement shall
occur, the entire unpaid Debt shall be automatically due and payable, without
any further notice, demand or other action by Lender or Mortgagee.

      Section 8.2 APPLICATION OF PROCEEDS. The purchase money, proceeds and
avails of any disposition of the Property, and or any part thereof, or any other
sums collected by Lender pursuant to the Note, this Security Instrument or the
other Loan Documents, may be applied by Lender to the payment of the Debt in
such priority and proportions as Lender in its discretion shall deem proper.

      Section 8.3 RIGHT TO CURE DEFAULTS. Upon the occurrence and during the
continuance of any Event of Default, Lender may, but without any obligation to
do so and without notice to or demand on Borrower and without releasing Borrower
from any obligation hereunder, make any payment or do any act required of
Borrower hereunder in such manner and to such extent as Lender may deem
necessary to protect the security hereof. Lender is authorized to enter upon the
Property for such purposes, or appear in, defend, or bring any action or
proceeding to protect its interest in the Property or to foreclose this Security
Instrument or collect the Debt, and the cost and expense thereof (including
reasonable attorneys' fees to the extent permitted by law), with interest as
provided in this Section 8.3, shall constitute a portion of the Debt and shall
be due and payable to Lender upon demand. All such costs and expenses incurred
by Lender in remedying such Event of Default or such failed payment or act or in
appearing in, defending, or bringing any such action or proceeding shall bear
interest at the Default Rate, for the period after notice from Lender that such
cost or expense was incurred to the date of payment to Lender. All such costs
and expenses incurred by Lender together with interest thereon calculated at the
Default Rate shall be deemed to constitute a portion of the Debt and be secured
by this Security Instrument and the other Loan Documents and shall be
immediately due and payable upon demand by Lender therefor.

      Section 8.4 ACTIONS AND PROCEEDINGS. Lender has the right to appear in and
defend any material action or material proceeding brought with respect to the
Property to protect its interest in the Property and to bring any material
action or material proceeding, in the name and on behalf of Borrower, which
Lender, in its reasonable discretion, decides should be brought to protect its
interest in the Property.

      Section 8.5 RECOVERY OF SUMS REQUIRED TO BE PAID. Subject to Article 15 of
the Loan Agreement, Lender shall have the right from time to time to take action
to recover any sum or sums which constitute a part of the Debt as the same
become due, without regard to whether or not the balance of the Debt shall be
due, and without prejudice to the right of Lender thereafter to bring an action
of foreclosure, or any other action, for a default or defaults by Borrower
existing at the time such earlier action was commenced.

      Section 8.6 OTHER RIGHTS, ETC. (a) The failure of Lender or Mortgagee to
insist upon strict performance of any term hereof shall not be deemed to be a
waiver of any term of this Security Instrument. Borrower shall not be relieved
of Borrower's obligations hereunder by reason of (i) the failure of Lender or


                                      -10-
<PAGE>

Mortgagee to comply with any request of Borrower or any guarantor or indemnitor
with respect to the Loan to take any action to foreclose this Security
Instrument or otherwise enforce any of the provisions hereof or of the Note or
the other Loan Documents, (ii) the release, regardless of consideration, of the
whole or any part of the Property, or of any person liable for the Debt or any
portion thereof, or (iii) any agreement or stipulation by Lender extending the
time of payment or otherwise modifying or supplementing the terms of the Note,
this Security Instrument or the other Loan Documents.(a) It is agreed that the
risk of loss or damage to the Property is on Borrower, and Lender shall have no
liability whatsoever for decline in the value of the Property, for failure to
maintain the Policies, or for failure to determine whether insurance in force is
adequate as to the amount of risks insured. Possession by Lender shall not be
deemed an election of judicial relief if any such possession is requested or
obtained with respect to any Property or collateral not in Lender's possession.

      (b) Lender may resort for the payment of the Debt to any other security
held by Lender in such order and manner as Lender, in its discretion, may elect.
Lender may take action to recover the Debt, or any portion thereof, or to
enforce any covenant hereof without prejudice to the right of Lender thereafter
to foreclose this Security Instrument. The rights of Lender under this Security
Instrument shall be separate, distinct and cumulative and none shall be given
effect to the exclusion of the others. No act of Lender or Mortgagee shall be
construed as an election to proceed under any one provision herein to the
exclusion of any other provision. Neither Lender nor Mortgagee shall be limited
exclusively to the rights and remedies herein stated but shall be entitled to
every right and remedy now or hereafter afforded at law or in equity.

      Section 8.7 RIGHT TO RELEASE ANY PORTION OF THE PROPERTY. Lender may
release any portion of the Property for such consideration as Lender may
reasonably require without, as to the remainder of the Property, in any way
impairing or affecting the lien or priority of this Security Instrument, or
improving the position of any subordinate lienholder with respect thereto,
except to the extent that the obligations hereunder shall have been reduced by
the actual monetary consideration, if any, received by Lender for such release,
and may accept by assignment, pledge or otherwise any other property in place
thereof as Lender may reasonably require without being accountable for so doing
to any other lienholder. This Security Instrument shall continue as a lien and
security interest in the remaining portion of the Property.

      Section 8.8 RIGHT OF ENTRY. Upon reasonable notice to Borrower, Lender and
its agents shall have the right to enter and inspect the Property at all
reasonable times.

      Section 8.9 BANKRUPTCY. (a) Upon or at any time after the occurrence of an
Event of Default, Lender shall have the right to proceed in its own name or in
the name of Borrower in respect of any claim, suit, action or proceeding
relating to the rejection of any Lease, including, without limitation, the right
to file and prosecute, to the exclusion of Borrower, any proofs of claim,
complaints, motions, applications, notices and other documents, in any case in
respect of the lessee under such Lease under the Bankruptcy Code.(a) If there
shall be filed by or against Borrower a petition under 11 U.S.C. ss.101 et seq.,
as the same may be amended from time to time (the "Bankruptcy Code"), and
Borrower, as lessor under any Lease, shall determine to reject such Lease
pursuant to Section 365(a) of the Bankruptcy Code, then Borrower shall give
Lender not less than ten (10) days' prior notice of the date on which Borrower
shall apply to the bankruptcy court for authority to reject the Lease. Lender
shall have the right, but not the obligation, to serve upon Borrower within such


                                      -11-
<PAGE>

ten-day period a notice stating that (i) Lender demands that Borrower assume and
assign the Lease to Lender pursuant to Section 365 of the Bankruptcy Code and
(ii) Lender covenants to cure or provide adequate assurance of future
performance under the Lease. If Lender serves upon Borrower the notice described
in the preceding sentence, Borrower shall not seek to reject the Lease and shall
comply with the demand provided for in clause (i) of the preceding sentence
within thirty (30) days after the notice shall have been given, subject to the
performance by Lender of the covenant provided for in clause (ii) of the
preceding sentence.

      Section 8.10 SUBROGATION. If any or all of the proceeds of the Note have
been used to extinguish, extend or renew any indebtedness heretofore existing
against the Property, then, to the extent of the funds so used, Lender shall be
subrogated to all of the rights, claims, liens, titles, and interests existing
against the Property heretofore held by, or in favor of, the holder of such
indebtedness and such former rights, claims, liens, titles, and interests, if
any, are not waived but rather are continued in full force and effect in favor
of Lender and are merged with the lien and security interest created herein as
cumulative security for the repayment of the Debt, the performance and discharge
of Borrower's obligations hereunder, under the Loan Agreement, the Note and the
other Loan Documents and the performance and discharge of the Other Obligations.

                        Article 9 - ENVIRONMENTAL HAZARDS

      Section 9.1 ENVIRONMENTAL COVENANTS. Borrower has provided representations
and warranties regarding environmental matters set forth in Section 12.1 of the
Loan Agreement and shall comply with the covenants regarding environmental
matters set forth in Section 12.2 of the Loan Agreement.

      Section 9.2 LENDER'S RIGHTS. Lender and any other person or entity
designated by Lender, including but not limited to any representative of a
Governmental Authority, and any environmental consultant, and any receiver
appointed by any court of competent jurisdiction, shall have the right, but not
the obligation, to enter upon the Property at all reasonable times to assess any
and all aspects of the environmental condition of the Property and its use,
including but not limited to conducting any environmental assessment or audit
(the scope of which shall be determined in Lender's sole discretion) and taking
samples of soil, groundwater or other water, air, or building materials, and
conducting other invasive testing. Borrower shall cooperate with and provide
access to Lender and any such person or entity designated by Lender.

                              Article 10 - WAIVERS

      Section 10.1 MARSHALLING AND OTHER MATTERS. Borrower hereby waives, to the
extent permitted by law, the benefit of all Legal Requirements now or hereafter
in force regarding appraisement, valuation, stay, extension, reinstatement and
redemption and all rights of marshalling in the event of any sale hereunder of
the Property or any part thereof or any interest therein. Further, Borrower
hereby expressly waives any and all rights of redemption from sale under any
order or decree of foreclosure of this Security Instrument on behalf of
Borrower, and on behalf of each and every person acquiring any interest in or
title to the Property subsequent to the date of this Security Instrument and on
behalf of all persons to the extent permitted by Legal Requirements.


                                      -12-
<PAGE>

      Section 10.2 WAIVER OF NOTICE. Borrower shall not be entitled to any
notices of any nature whatsoever from Lender or Mortgagee except with respect to
matters for which this Security Instrument or the Loan Agreement specifically
and expressly provides for the giving of notice by Lender or Mortgagee to
Borrower and except with respect to matters for which Borrower is not permitted
by Legal Requirements to waive its right to receive notice, and Borrower hereby
expressly waives the right to receive any notice from Lender or Mortgagee with
respect to any matter for which this Security Instrument does not specifically
and expressly provide for the giving of notice by Lender or Mortgagee to
Borrower.

      Section 10.3 WAIVER OF STATUTE OF LIMITATIONS. Borrower hereby expressly
waives and releases to the fullest extent permitted by law, the pleading of any
statute of limitations as a defense to payment of the Debt or performance of its
Other Obligations.

      Section 10.4 SOLE DISCRETION OF LENDER. Whenever pursuant to this Security
Instrument, Lender exercises any right given to it to approve or disapprove, or
any arrangement or term is to be satisfactory to Lender, the decision of Lender
to approve or disapprove or to decide whether arrangements or terms are
satisfactory or not satisfactory shall (except as is otherwise specifically
herein provided) be in the sole discretion of Lender and shall be final and
conclusive.

      Section 10.5 WAIVER OF TRIAL BY JURY. BORROWER AND LENDER EACH HEREBY
AGREES NOT TO ELECT A TRIAL BY JURY OF ANY ISSUE TRIABLE OF RIGHT BY JURY, AND
WAIVES ANY RIGHT TO TRIAL BY JURY FULLY TO THE EXTENT THAT ANY SUCH RIGHT SHALL
NOW OR HEREAFTER EXIST WITH REGARD TO THE LOAN DOCUMENTS, OR ANY CLAIM,
COUNTERCLAIM OR OTHER ACTION ARISING IN CONNECTION THEREWITH. THIS WAIVER OF
RIGHT TO TRIAL BY JURY IS GIVEN KNOWINGLY AND VOLUNTARILY BY BORROWER AND
LENDER, AND IS INTENDED TO ENCOMPASS INDIVIDUALLY EACH INSTANCE AND EACH ISSUE
AS TO WHICH THE RIGHT TO A TRIAL BY JURY WOULD OTHERWISE ACCRUE. EACH OF LENDER
AND BORROWER IS HEREBY AUTHORIZED TO FILE A COPY OF THIS PARAGRAPH IN ANY
PROCEEDING AS CONCLUSIVE EVIDENCE OF THIS WAIVER BY BORROWER AND LENDER.

      Section 10.6 WAIVER OF FORECLOSURE DEFENSE. Borrower hereby waives any
defense Borrower might assert or have by reason of Lender's failure to make any
tenant or lessee of the Property a party defendant in any foreclosure proceeding
or action instituted by Lender.

      SECTION 10.7 FAILURE TO ACT. Notwithstanding anything to the contrary
contained herein or in any other Loan Document, the failure of Mortgagee to take
any action hereunder or under any other Loan Document shall not (i) be deemed to
be a waiver of any term or condition of this Security Instrument or any of the
other Loan Documents, (ii) adversely effect any rights of Lender hereunder or
under any other Loan Document and (iii) relieve Borrower of any of Borrower's
obligations hereunder or under any other Loan Document.


                                      -13-
<PAGE>

                            Article 11 - EXCULPATION

      Section 11.1 EXCULPATION. The provisions of Article 15 of the Loan
Agreement are hereby incorporated by reference into this Security Instrument to
the same extent and with the same force as if fully set forth herein.

                              Article 12 - NOTICES

      Section 12.1 NOTICES. All notices or other written communications
hereunder shall be delivered in accordance with Article 16 of the Loan
Agreement.

      Section 12.2 ADDRESSES. Notices to Mortgagee hereunder and under each
other Loan Document shall include a copy thereof to Lender (to be addressed and
delivered in accordance with the Loan Agreement) and shall to be sent as
follows:

                  MERS Commercial
                  P.O. Box 2300
                  Flint, Michigan 48501-2300
                  Attention: Corporate Secretary
                  Facsimile No.: (703) 748-0183

                           Article 13 - APPLICABLE LAW

      Section 13.1 GOVERNING LAW. This Security Instrument shall be governed,
construed, applied and enforced in accordance with the laws of the state in
which the Property is located and applicable laws of the United States of
America.

      Section 13.2 PROVISIONS SUBJECT TO APPLICABLE LAW. All rights, powers and
remedies provided in this Security Instrument may be exercised only to the
extent that the exercise thereof does not violate any applicable provisions of
law and are intended to be limited to the extent necessary so that they will not
render this Security Instrument invalid, unenforceable or not entitled to be
recorded, registered or filed under the provisions of any applicable law. If any
term of this Security Instrument or any application thereof shall be invalid or
unenforceable, the remainder of this Security Instrument and any other
application of the term shall not be affected thereby.

                            Article 14 - DEFINITIONS

      Section 14.1 DEFINED TERMS. Unless the context clearly indicates a
contrary intent or unless otherwise specifically provided herein, words used in
this Security Instrument may be used interchangeably in singular or plural form
and the word "Borrower" shall mean "each Borrower and any subsequent owner or
owners of the Property or any part thereof or any interest therein," the word
"Lender" shall mean "Lender and any subsequent holder of the Note," the word
"Note" shall mean "the Note and any other evidence of indebtedness secured by
this Security Instrument," the word "Property" shall include any portion of the
Property and any interest therein, and the phrases "attorneys' fees", "legal
fees" and "counsel fees" shall include any and all reasonable attorneys',
paralegal and law clerk fees and disbursements, including, but not limited to,
fees and disbursements at the pre-trial, trial and appellate levels incurred or
paid by Lender in protecting its interest in the Property, the Leases and the
Rents and enforcing its rights hereunder.


                                      -14-
<PAGE>

                      Article 15 - MISCELLANEOUS PROVISIONS

      Section 15.1 NO ORAL CHANGE. This Security Instrument, and any provisions
hereof, may not be modified, amended, waived, extended, changed, discharged or
terminated orally or by any act or failure to act on the part of Borrower or
Lender, but only by an agreement in writing signed by the party against whom
enforcement of any modification, amendment, waiver, extension, change, discharge
or termination is sought.

      Section 15.2 SUCCESSORS AND ASSIGNS. This Security Instrument shall be
binding upon and inure to the benefit of (a) Mortgagee and Lender and their
respective successors and assigns forever and (b) Borrower and its permitted
successors and assigns forever.

      Section 15.3 INAPPLICABLE PROVISIONS. If any term, covenant or condition
of the Loan Agreement, the Note or this Security Instrument is held to be
invalid, illegal or unenforceable in any respect, the Loan Agreement, the Note
and this Security Instrument shall be construed without such provision.

      Section 15.4 HEADINGS, ETC. The headings and captions of various Sections
of this Security Instrument are for convenience of reference only and are not to
be construed as defining or limiting, in any way, the scope or intent of the
provisions hereof.

      Section 15.5 NUMBER AND GENDER. Whenever the context may require, any
pronouns used herein shall include the corresponding masculine, feminine or
neuter forms, and the singular form of nouns and pronouns shall include the
plural and vice versa.

      Section 15.6 ENTIRE AGREEMENT. This Security Instrument and the other Loan
Documents contain the entire agreement of the parties hereto and thereto in
respect of the transactions contemplated hereby and thereby, and all prior
agreements among or between such parties, whether oral or written between
Borrower and Lender are superseded by the terms of this Security Instrument and
the other Loan Documents.

      Section 15.7 LIMITATION ON LENDER'S RESPONSIBILITY. No provision of this
Security Instrument shall operate to place any obligation or liability for the
control, care, management or repair of the Property upon Lender or Mortgagee,
nor shall it operate to make Lender or Mortgagee responsible or liable for any
waste committed on the Property by the tenants or any other Person, or for any
dangerous or defective condition of the Property, or for any negligence in the
management, upkeep, repair or control of the Property resulting in loss or
injury or death to any tenant, licensee, employee or stranger. Nothing herein
contained shall be construed as constituting Lender or Mortgagee a "mortgagee in
possession."

                         Article 16 - STATUS OF PARTIES

      Section 16.1 STATUS OF BORROWER. Borrower's exact legal name is correctly
set forth in the first paragraph of this Security Instrument and the signature
block at the end of this Security Instrument. Borrower is an organization of the
type specified in the first paragraph of this Security Instrument. Borrower is


                                      -15-
<PAGE>

incorporated in or organized under the laws of the state specified in the first
paragraph of this Security Instrument. Borrower's principal place of business
and chief executive office, and the place where Borrower keeps its books and
records, including recorded data of any kind or nature, regardless of the medium
or recording, including software, writings, plans, specifications and
schematics, has been for the preceding four months (or, if less, the entire
period of the existence of Borrower) the address of Borrower set forth on the
first page of this Security Instrument. Except as permitted by the Loan
Agreement, Borrower will not change or permit to be changed (a) Borrower's name,
(b) Borrower's identity (including its trade name or names), (c) Borrower's
principal place of business set forth on the first page of this Security
Instrument, (d) the corporate, partnership or other organizational structure of
Borrower, (e) Borrower's state of organization, or (f) Borrower's organizational
number, without notifying Lender of such change in writing at least thirty (30)
days prior to the effective date of such change and, in the case of a change in
Borrower's structure, without first obtaining the prior written consent of
Lender. If Borrower does not now have an organizational identification number
and later obtains one, Borrower promptly shall notify the Lender of such
organizational identification number.

      Section 16.2 MORTGAGEE AS NOMINEE. (a) Mortgagee is acting as nominee
under certain agreements by and between Lender and Mortgagee as the same may
have been or may be amended, restated, replaced, supplemented or otherwise
modified from time to time. (b) Notwithstanding anything to the contrary
contained herein or in any other Loan Document, all references herein and in any
other Loan Document to "Lender" shall be deemed to collectively or individually
(as the context requires) refer to Lender or to Mortgagee acting on behalf of
and at the sole direction of Lender in its capacity as Lender's nominee. (c)
Unless Lender, in its sole discretion, shall determine otherwise, only Lender
(and not Mortgagee) shall be deemed to be "Lender" with respect to (i) any
consent, determination or similar approval right granted to Lender under the
Loan Documents (including, without limitation, any consent or similar approval
right that is deemed granted if not approved or denied within a specified time
period), (ii) any items, documents or other information required to be delivered
to Lender under the Loan Documents (other than notices) or (iii) any future
funding or other obligations of Lender to Borrower or any affiliate of Borrower
under the Loan Documents, if any.

                   Article 17 - MINNESOTA SPECIFIC PROVISIONS

      Section 17.1 Inconsistencies. In the event of any inconsistencies between
the terms and conditions of this Article 17 and the other provisions of this
Security Instrument, or to the extent, and only to the extent, any of the
provisions in this Article 17 conflict with, or are ambiguous when read together
with, any of the provisions of this Security Instrument, the provisions of this
Article 17 shall govern. The provisions of this Article 17 are intended to
supplement and not replace the remedies and other terms and provisions contained
in the Security Instrument.

      Section 17.2 Security Instrument Registry Tax. Borrower agrees to pay, or
to promptly reimburse Lender for the payment of, the amount of the mortgage
registry tax payable with respect to and upon the recording of this Security
Instrument in accordance with Minnesota Statutes Section 287.05.


                                      -16-
<PAGE>

      Section 17.3 Fixture Financing Statement. This Security Instrument shall
be deemed to be a fixture financing statement within the meaning of the Uniform
Commercial Code and for such purpose, the following information is given:


      Name and address of Debtor:            FSP 50 South Tenth Street Corp.
                                             401 Edgewater Place, Suite 200
                                             Wakefield, Massachusetts 01880-6210
                                             Attention: ____________________

      Type of organization:                  corporation

      Jurisdiction of organization:          Delaware

      Organization ID No.:                   ________________________

      Federal Taxpayer ID No.:               _____________________

      Name and address of Secured Party:     _____________________
                                             _____________________
                                             _____________________
                                             Attention: ____________________

      Description of the types               The Property and collateral
      (or items) of property                 described in Article I which is
      covered by this Financing              subject to the Uniform Commercial
      Statement:                             Code

      Description of real estate to          Those certain tracts of land,
      which the collateral is attached       described on Exhibit A
      or upon which it is or will be
      located:

      Record owner of real estate to which   Borrower
      the collateral is attached or upon
      which it is or will be located:

Some of the above-described collateral is or is to become fixtures upon the
above described real estate and this Security Instrument is to be filed for
record in the public real estate records of the county or counties in which the
fixtures are, or are to be, located.

      Section 17.4 Remedies of Lender; Security Instrument Foreclosure. Borrower
does hereby grant and confer upon Lender the fullest rights and remedies
available for foreclosure of this Security Instrument by action or by
advertisement pursuant to Minnesota Statutes Chapters 580, 581 and 582, as said
statutes may be amended from time to time, and pursuant to other applicable
Minnesota laws and statutes, as amended, governing and authorizing mortgage
foreclosures by action and by advertisement including, but not limited to, a
grant to Lender of the power of sale; and the power of sale granted Lender in
this Security Instrument shall include, without limitation, the power of sale
required to permit, at Lender's option, lawful foreclosure of this Security


                                      -17-
<PAGE>

Instrument by advertisement in accordance with the statutes then made and
provided. Upon the occurrence of an Event of Default and at any time thereafter
until such Event of Default is cured, Lender may, at its option, exercise any or
all of the following rights and remedies:

      (a) Foreclose this Security Instrument by judicial action or
advertisement, and Borrower hereby authorizes Lender to do so, power being
herein expressly granted to sell any or all of the Property at public auction
and to convey the same to the purchaser, in fee simple, pursuant to the statutes
of Minnesota, or

      (b) proceed under the Uniform Commercial Code (or the Uniform Commercial
Code as adopted by the state of the Borrower's organization) and exercising such
rights and remedies as may be provided to a secured party by the Uniform
Commercial Code with respect to all or any portion of the Property which are
fixtures or personal property.

      Section 17.5 Assignment of Rents and Leases; Receiver.

      (a) The Mortgage constitutes an assignment of leases and rents within the
meaning of Minnesota Statutes Sections 559.17 and 576.01, and is intended to
comply fully with the provisions thereof, and to afford Lender, the rights and
remedies of a secured lender under those statutes.

      (b) The exercise by Lender of the statutory remedies referenced in this
paragraph shall not constitute Lender a "mortgagee-in-possession" under
Minnesota law.

      (c) All Rents collected by Lender, its agent or a receiver under this
Security Instrument, if any, shall be held and applied in the following order:

            (i) To payment of all reasonable fees of the receiver, if one shall
      be appointed, approved by the court;

            (ii) To the repayment when due of all tenant security deposits, with
      interest thereon, pursuant to the provisions of Minnesota Statutes Section
      504B.178;

            (iii) To payment when due of all delinquent or current real estate
      taxes and special assessments payable with respect to the Property, or the
      periodic escrow for the payment of said taxes or special assessments;

            (iv) To payment when due of all premiums for the insurance required
      by the provisions of this Security Instrument, or the periodic escrow for
      the payment of said premiums;

            (v) To payment of expenses incurred for normal maintenance of the
      Property;

            (vi) If received prior to any foreclosure sale of the Property
      pursuant to this Security Instrument, to Lender for payment of the
      indebtedness secured hereby, but no such payment made after acceleration
      of the indebtedness secured hereby shall affect such acceleration;

            (vii) If received during or with respect to the period of redemption
      after a foreclosure sale of the Property pursuant to this Security
      Instrument:


                                      -18-
<PAGE>

                  (1) If the purchaser at the foreclosure sale is not Lender,
            first to Lender to the extent of any deficiency of the sale proceeds
            to repay the indebtedness secured hereby, second to the purchaser as
            a credit to the redemption price, but if the Property is not
            redeemed, then to the purchaser of the Property;

                  (2) If the purchaser at the foreclosure sale is Lender, to
            Lender to the extent of any deficiency of the sale proceeds to repay
            the indebtedness secured hereby and the balance to be retained by
            Lender as a credit to the redemption price, but if the Property is
            not redeemed, then to Lender, whether or not any such deficiency
            exists.

The rights and powers of Lender and receivers under this Security Instrument and
the application of Rents under this paragraph shall continue until expiration of
the redemption period from any foreclosure sale, whether or not any deficiency
remains after a foreclosure sale.

      (d) If Lender makes any advances to a receiver, or otherwise for the
benefit of the Property, such advances shall become indebtedness secured by this
Security Instrument.

      Section 17.6 Maturity. The latest maturity date for any of the
indebtedness evidenced by the Note secured by this Security Instrument is
January 1, 2012.

                         [NO FURTHER TEXT ON THIS PAGE]


                                      -19-
<PAGE>


      IN WITNESS WHEREOF, THIS Security Instrument has been executed by the
undersigned as the day and year first above written.

                                  BORROWER:

                                  FSP 50 SOUTH TENTH STREET CORP., a
                                  Delaware corporation

                                  By: /s/ George J. Carter
                                      ----------------------------------------
                                      Name: George J. Carter, President
                                      Title:

                   [Signatures Continue on the Following Page]

<PAGE>

                                  LENDER:


                                  BANK OF AMERICA, N.A., a national
                                  banking association


                                  By: /s/ Dean Ravosa
                                      --------------------------------
                                      Name: Dean Ravosa
                                      Title: Principal

<PAGE>

                                  MASTER LESSEE:

                                  FSP 50 SOUTH TENTH STREET LLC,
                                  a Delaware limited liability company

                                  By: /s/ George J. Carter
                                      -------------------------------------
                                      Name: George J. Carter, President
                                      Title:

                   [Signatures Continue on the Following Page]


<PAGE>

COMMONWEALTH OF MASSACHUSETTS :
                                    : ss
COUNTY OF MIDDLESEX                 :

      On this 18th day of December, 2006, before me, the undersigned notary
public, personally appeared George J. Carter, President of FSP 50 South Tenth
Street Corp., a Delaware corporation, proved to me through satisfactory evidence
of identification, which was personal knowledge of identity, to be the person
whose name is signed on the preceding or attached document, and acknowledged to
me that he signed it voluntarily, as the act and deed of said entity for its
stated purpose.


                        /s/ Barbara J. Fournier
                        --------------------------------------------
                        Official Signature and Seal of Notary Public

[NOTARY SEAL]

<PAGE>

COMMONWEALTH OF MASSACHUSETTS :
                                    : ss
COUNTY OF MIDDLESEX                 :

      On this 18th day of December, 2006, before me, the undersigned notary
public, personally appeared George J. Carter, President of FSP 50 South Tenth
Street LLC, a Delaware limited liability company, proved to me through
satisfactory evidence of identification, which was personal knowledge of
identity, to be the person whose name is signed on the preceding or attached
document, and acknowledged to me that he signed it voluntarily, as the act and
deed of said entity for its stated purpose.

                        /s/ Barbara J. Fournier
                        --------------------------------------------
                        Official Signature and Seal of Notary Public

[NOTARY SEAL]

<PAGE>

STATE OF NEW YORK

COUNTY OF ROCKLAND

            I, Patricia Hennessy Cuevas, a Notary Public of the County and State
aforesaid, certify that Dean C. Ravosa, personally came before me this day and
acknowledged that he is a Principal of Bank of America, N.A., a national banking
association, that executed the foregoing instrument, and acknowledged to me that
the same was the act of the said association, and that he executed the same as
the act of such association for the purposes and consideration therein expressed
and in the capacity therein stated.

       WITNESS my hand and official stamp or seal, this 21st day of
December, 2006

                                                /s/ Patricia Hennessy Cuevas
                                                ------------------------------
                                                Notary Public Signature

My Commission Expires:

    [NOTARY STAMP]
----------------------
    (Notary Seal)