PURCHASE AGREEMENT

THIS AGREEMENT ("Agreement") is made and entered into by and between (i) 
AQUILA BIOPHARMACEUTICALS, INC., A DELAWARE CORPORATION ("SELLER") and (ii) 
ALEXANDRIA REAL ESTATE EQUITIES, INC., A MARYLAND CORPORATION ("Purchaser"), 
to provide for the purchase and sale of the property herein described.

IN CONSIDERATION OF TEN DOLLARS ($10.00), and other good and valuable 
consideration, the receipt and sufficiency of which are hereby acknowledged, 
Seller and Purchaser agree as follows:

                             ARTICLE I - SALE OF PROPERTY

    SECTION 1. 1 . Seller shall sell to Purchaser, and Purchaser shall 
purchase from Seller, upon the terms and conditions hereinafter set forth, 
all of Seller's right, title, and interest (if any) in and to the following 
property: (i) those two (2) parcels of land located in Rockville, Montgomery 
County, Maryland, and described in EXHIBIT "A" attached hereto, together with 
all rights, privileges and easements appurtenant thereto or used in 
connection therewith, including, without limitation, all minerals, oil, gas 
and other hydrocarbon substances thereon, all development rights, air rights, 
water, water rights and water stock relating thereto (the "Land"); (ii) the 
building and improvements located on the Land (the "Improvements"), which are 
commonly known as 1500 East Gude Drive, 3 Taft Court and 3-1/2 Taft Court, 
including all fixtures used in connection with the operation or occupancy of 
the Land and the improvements, such as heating, air conditioning, electrical, 
plumbing, security and mechanical systems and facilities used to provide any 
utility services, refrigeration, waste disposal and other services; (iii) all 
appliances, furnishings, furniture, fixtures, machinery, heating, ventilating 
and air conditioning equipment, maintenance equipment, supplies, tools, and 
other personal property attached to, located at or used in connection with 
the management, operation, maintenance and repair of the Land and/or 
Improvements, a complete list of which is attached hereto as EXHIBIT "B"; 
(iv) any land lying in the bed of any street, road, avenue or alley, open or 
closed, in front of or adjoining the Land, to the center line thereof; and 
(v) ( 1 ) all tenant leases, (2) rents and profits from and after the Closing 
Date, (3) all security and/or tenant deposits, and other deposits, as more 
fully described in Section 10.2 hereof, and (4) all intangible property now 
or hereafter owned by Seller and UseD in connection with the Land, the 
Improvements or the personal property, including, without limitation, the 
Service Contracts (as hereinafter defined), building and trademark and trade 
names, business licenses, architectural, site, landscaping and other permits, 
applications, approvals, authorizations and other entitlements, guarantees 
and warranties, all contract rights, books, records, reports, test results, 
environmental assessments, as-built plans, specifications and other similar 
documents and materials relating to the use, operation, maintenance or repair 
of the Property or the construction or fabrication thereof, all utility 
contracts, and all franchises, relating to the




                                          2

operation of the Property which are owned by Seller, to the extent same are 
assignable. (All of the foregoing real and personal property is herein 
collectively referred to as the "Property").

                        ARTICLE II - PURCHASE PRICE; DEPOSIT

    SECTION 2.1. The purchase price for the Property shall be SIX MILLION 
FIVE HUNDRED THOUSAND DOLLARS ($6,500,000.00) (the "Purchase Price"), 
subject, however, to the adjustments and prorations provided for herein.

    SECTION 2.2. The Purchase Price shall be paid to Seller by Purchaser by 
wire transfer of immediately available funds for credit at Closing, and the 
Deposit (as hereinafter defined) shall be applied to the Purchase Price.

    SECTION 2.3. Purchaser shall, not later than three (3) business days 
after the receipt by Purchaser of a fully executed original of this 
Agreement, deliver to Chicago Title Insurance Company (the "Escrow Agent" 
and/or the "Title Company"), with its business offices located at 51 Monroe 
Street, Penthouse III, Rockville, Maryland 20850, as escrow agent, as a good 
faith earnest money deposit hereunder, the amount of Three Hundred 
Twenty-Five Thousand Dollars ($325,000.00) (such deposit and all interest 
thereon is hereinafter referred to as the "Deposit"), by wire transfer of 
immediately available funds. Escrow Agent shall deposit the funds comprising 
the Deposit in a money market account, overnight repurchase agreements, or 
other similar federally-insured investments, as directed by Purchaser and 
reasonably approved by Seller. Within four (4) business days of receipt of 
the Deposit, Escrow Agent shall give written notice to Seller and Purchaser 
of its receipt of the Deposit, and of the name of the institution and the 
account number in which the Deposit shall be held. The Deposit shall be held 
and delivered by the Escrow Agent in accordance with the provisions of this 
Agreement.

            ARTICLE III - RIGHT OF ACCESS TO PROPERTY - FEASIBILITY

    SECTION 3.1  Purchaser, and Purchaser's attorneys, accountants, 
employees, agents, contractors, and representatives shall have the right at 
any time and from time to time after the Execution Date (as defined in the 
last paragraph of this Agreement) to examine and review all data and 
financial information relating to the Property, to make studies, perform 
financial analyses and inspect the Property for defects, to survey and make 
other tests, including, without limitation, physical, structural, mechanical, 
architectural, engineering, soils, geo-technical and environmental/asbestos 
tests, all at Purchaser's sole cost and expenses. Any and all entries by 
Purchaser and/or its representatives, agents, employees or contractors upon 
the Property shall be subject to the rights of tenants in and to the 
Improvements and the Land. All such studies shall be conducted in a 
reasonable manner by Purchaser, and by its representatives, agents, employees 
or contractors, and all entries



                                          3

into the Improvements shall be conducted during normal business hours. In the 
event that Purchaser's studies require access to occupied space of a tenant, 
then Purchaser shall give Seller not less than twenty-four (24) hours 
telephone notice of its desire to inspect the premises; in the event that 
Purchaser's studies do not require access to occupied space of a tenant, then 
Purchaser shall give Seller reasonable advance telephone notice of its 
inspection of the premises. Purchaser shall conduct its studies in a manner 
so as not to unreasonably interfere with the business operations of Seller or 
of any of the tenants of the Property. Neither Purchaser nor Purchaser's 
representatives, agents, employees or contractors shall disclose to tenants 
of the Property the possible sale of the Property by Seller. Seller (or a 
representative of Seller) shall have the right to accompany Purchaser and/or 
its representatives, agents, employees or contractors to any meeting with a 
tenant. Seller agrees to cooperate with Purchaser in such investigations and 
reviews, at no cost to Seller. Purchaser, its representatives, agents, 
employees, and contractors shall maintain public liability insurance policies 
insuring against claims arising as a result of the studies of the Property 
being conducted by Purchaser. Before entering the Property to conduct any 
studies therein, Purchaser shall supply Seller with individual insurance 
certificates naming Seller as an additional insured. Purchaser shall conduct 
no destructive testing or examinations on the Property without first 
acquiring Seller's prior written consent to the scope, nature and locations 
of such tests and examinations, which consent shall not be unreasonably 
withheld, conditioned or delayed (but subject to the rights of tenants of the 
Property at all times). Purchaser shall, and hereby does, indemnify, defend 
and hold Seller harmless from any loss, costs (including reasonable 
attorneys' fees), liability or damages which Seller or the Property may 
suffer or incur resulting from the activities of Purchaser or Purchaser's 
employees, agents, representatives and contractors, including without 
limitation, liability for mechanics' lien claims. Purchaser shall promptly 
repair any and all damage to the Property caused by Purchaser, or by any of 
Purchaser's employees, agents, representatives or contractors in the course 
of their studies, inspections, and other activities on the Property prior to 
the Closing Date. The obligations of Purchaser described in this Section 
shall survive termination or expiration of this Agreement.

    SECTION 3.2  Not later than three (3) Business Days after the Execution 
Date, Seller shall deliver or make available to Purchaser, copies of all 
contracts, documents, leases, reports, books, records and other materials 
relating to the Property which are within its possession or control, 
including, without limitation, as-built plans and tests, soil tests, 
structural and mechanical reports, environmental studies, maps, plans, 
agreements, governmental permits and approvals, surveys, construction 
warranties, an appraisal of the Land and Improvements performed in 1991, and 
land studies; and expressly including a copy of the year-end 1996 Operating 
Statements for the Property and a copy of the year-to-date 1997 Operating 
Statements for the Property as described in Section 6.1.(I) hereof; current 
rent roll for the Property as described in Section 6.1(J) hereof; copies of 
all Leases as identified in Section 6.1 (J) hereof; copies of the most recent 
bills for real estate taxes and



                                          4

insurance premiums received by Seller which pertain to the Property; copies 
of all Service Contracts as identified in Section 6.1 (K) hereof; and a copy 
of Seller's Owner's Title Insurance Policy pertaining to the Property (but 
expressly excluding any internal evaluations or attorney-client privileged 
materials) (collectively, the "Seller's Documents").

    SECTION 3.3  Promptly after the Execution Date, Seller shall submit to 
bioMerieux, Inc. ("BMI") and to BTRL Contracts and Services, Inc. ("BTRL"), 
both of the tenants of the Property under the Leases, an estoppel 
certificate, substantially in the form of attached EXHIBIT "G". Each of said 
estoppel certificates is referred to individually hereinafter as an "Estoppel 
Certificate", or collectively as the "Estoppel Certificates". Within 
twenty-five (25) days after the Execution Date, Seller shall deliver to 
Purchaser an Estoppel Certificate executed by BMI, provided that so long as 
Seller has used reasonable efforts to acquire same from BMI, it shall not be 
deemed to be in default of any of its obligations under this Agreement in the 
event that BMI refuses to deliver the Estoppel Certificate substantially in 
the form of attached EXHIBIT "G", or to deliver any estoppel certificate at 
all. Within the aforesaid twenty-five (25) day period after the Execution 
Date, Seller shall also deliver to Purchaser an Estoppel Certificate from 
BTRL if the same is received by Seller. Within the Study Period, (as such 
term is hereinafter defined), Purchaser shall review, and shall approve or 
disapprove, each of the Estoppel Certificates delivered by Seller to 
Purchaser, in Purchaser's sole discretion. Other than as set forth herein, 
Seller shall have no obligation to acquire estoppel certificates from tenants 
in connection with the sale of the Property to Purchaser.

    SECTION 3.4  Notwithstanding anything herein to the contrarY, if Purchaser 
determines in its sole and absolute discretion that the Property, or any 
information acquired by Purchaser as a result of its studies concerning same 
(including, without limitation, any information contained in any of the 
Estoppel Certificates acquired by Seller and delivered to Purchaser, or any 
information contained in the Title Commitment, the Survey or the UCC Searches 
acquired by Purchaser which Seller does not expressly agree to cure in the 
manner provided in Section 4.1), is unacceptable to Purchaser in any respect, 
then in any such event, Purchaser shall have the right at its sole option to 
terminate this Agreement by written notice sent to and received by Seller on 
or before 5:00 p.m. East Coast time on the thirtieth (30th) calendar day 
following the receipt by Purchaser of a fully executed original of this 
Agreement. The period between such date and 5:00 p.m. East Coast time on the 
thirtieth (30th) calendar day following such date is herein referred to as 
the "Study, Period". Upon termination of this Agreement by Purchaser during 
the Study Period as aforesaid, Purchaser will return to Seller all of the 
Seller's Documents previously delivered to Purchaser; Purchaser shall repair 
any damage to the Property caused by its studies and investigations; the 
Deposit shall be returned to Purchaser; and the parties shall be relieved of 
all furtherr obligations hereunder (except as otherwise expressly set forth 
herein). If Purchaser terminates this Agreement prior to the end of the Study 
Period as permitted hereby,




                                          5

Purchaser shall keep confidential all information and material pertaining to 
the Property which was acquired by it during the Study Period (other than as 
required by applicable law or regulation), which obligation of 
confidentiality shall expire on the second (2nd) anniversary following the 
date of termination of this Agreement by Purchaser.

    If Seller shall not receive Purchaser's notice terminating this Agreement 
prior to 5:00 p.m. East Coast time on the last day of the Study Period, then 
this Agreement shall remain in full force and effect and the parties shall 
proceed to Closing in the manner set forth herein.

    Notwithstanding anything to the contrary contained in this Agreement, 
wherever a reference is made herein to a return of the Deposit to Purchaser 
after a termination of this Agreement, if there exists on the date the 
Deposit is to be returned to Purchaser any damage to the Property which 
Purchaser is obligated to repair, a portion of the Deposit in an amount 
reasonably determined by the parties to be sufficient to repair said damage 
shall continue to be held by Escrow Agent in escrow until the damage is 
repaired, after which time it shall be returned promptly to Purchaser. Seller 
shall have the right to use said funds to repair the Property in the event 
that all such damage to the Property has not been repaired by Purchaser 
within thirty (30) days after the date of termination of this Agreement; 
provided, however, the establishment of said escrow shall not limit or in any 
way mitigate Purchaser's obligation to pay for the full cost of repairing all 
damage to the Property caused by its studies, tests and examinations.

                      ARTICLE IV - TITLE AND PROPERTY CONDITION

    SECTION 4.1. Not later than twenty (20) days after the Execution Date, 
Purchaser shall have obtained a Commitment for Title Insurance (the "Title 
Commitment") issued by the Title Company, together with legible copies of all 
documents referenced as exceptions therein describing encumbrances, liens 
and/or defects in title that would affect the value or use of the Property. 
Not later than twenty-five (25) days after the Execution Date, Purchaser also 
shall have obtained (a) a current As-Built American Land Title Association 
survey of the Property (the "Survey"), in form reasonably satisfactory to 
Purchaser, the Title Company and any lenders designated by Purchaser (the 
"New Lenders"), prepared and certified to Purchaser, the Title Company, the 
New Lenders, and such other persons or entities as Purchaser may, in its 
discretion, request, by a surveyor licensed in the State of Maryland, showing 
any and all matters which Purchaser and the New Lenders may reasonably 
require, including, without limitation, all Improvements, all easements, all 
roads, all utilities, the number of parking spaces, access to and from the 
Land, and drainage ditches, set-back lines, protrusions, encroachments, and 
encumbrances affecting the same; and (b) a UCC Search with regard to the 
personal property included in the sale (the "UCC Search").


                                           

                                          6

    Purchaser shall have until the last day of the Study Period to notify 
Seller in writing of any objection which Purchaser may have to any exception 
reported in the Title Commitment or matter shown on the Survey or the UCC 
Search (or any updates thereof, but, as to such updates, only as to matters 
arising during the period of time after the effective date of the Title 
Commitment the Survey, or the UCC Search [as applicable]; provided, however, 
that if any such updates are received by Purchaser, Purchaser shall have an 
additional five (5) Business Days, regardless of the occurrence of the last 
day of the Study Period, following Purchaser's receipt of such update to 
notify Seller of objections to items shown on any such update). Exceptions 
reported in the Title Commitment and matters shown on the Survey or the UCC 
Search (or any updates thereof) not objected to by Purchaser as provided 
above, as well as any other matters or exceptions which existed prior to the 
effective date of the Title Commitment, the Survey or the UCC Search (as 
applicable) which were not reported therein, shall be deemed to be "Permitted 
Exceptions." Seller shall notify Purchaser within three (3) Business Days of 
receipt of written notice of Purchaser's objection to title whether it shall 
take action to remove from title to the Property any exceptions and matters 
so objected to by Purchaser. The failure of Seller to so notify Purchaser 
shall be deemed an election by Seller to take no action. If Seller elects not 
to take such action, then any such matter objected to by Purchaser shall be 
deemed a Permitted Exception unless Purchaser terminates this Agreement by 
the date which is the later to occur of (i) three (3) Business Days after 
receipt of Seller's notice electing whether to take such remedial action (or 
the expiration of the aforesaid 3 Business Day period during which Seller 
failed to respond), or (ii) the last day of the Study Period. As a condition 
to Closing, Seller shall take all action necessary either (y) to remove from 
title to the Property any exceptions and matters so objected to by Purchaser 
which Seller has elected to cure in the manner set forth above, or in the 
alternative, (z) to obtain for Purchaser title insurance insuring over such 
exceptions or matters which Seller has elected to cure, such insurance to be 
in form and substance satisfactory to Purchaser, as determined in its 
reasonable discretion. If, prior to the Closing, Seller is unable to remove 
or satisfactorily insure over any exceptions or matters objected to by 
Purchaser which Seller has elected to cure in the manner set forth above, and 
Purchaser is unwilling to take title subject thereto, then, Purchaser may 
terminate this Agreement (in which case Escrow Agent shall return the Deposit 
to Purchaser, Purchaser shall repair any damage to the Property caused by 
Purchaser or its representatives, employees, agents or contractors, and 
neither party shall thereafter have any rights or obligations to the other 
hereunder); PROVIDED, HOWEVER, that if such objected to exceptions or matters 
as described above are not removed by the Closing Date (after Seller elected 
to do so) Purchaser may elect, upon written notice delivered to Seller on or 
prior to such date, to (a) extend the Closing Date to allow Seller a 
reasonable period of time to remove such objected to exceptions or matters or 
(b) proceed to a timely Closing whereupon such objected to exceptions or 
matters shall be deemed Permitted Exceptions. Seller shall in any event be 
required to discharge and remove any and all liens and encumbrances affecting 
the Property which secure an obligation to pay money (other than installments 
of




                                       7

real estate taxes not delinquent as of the Closing) and, even though 
Purchaser does not expressly disapprove such liens and encumbrances, such 
liens shall not be Permitted Exceptions.

    SECTION 4.2. Seller covenants and agrees not to create or consent to the 
imposition of any lien, encumbrance, easement, reservation, limitation, 
covenant, condition or restriction upon the Property between the Execution 
Date and the Closing Date without obtaining the prior written consent of 
Purchaser.

    SECTION 4.3. CONDITION OF PROPERTY. Other than as expressly set forth in 
this Agreement, at the Closing, Seller shall deliver the Property to 
Purchaser in the same "AS IS, WHERE IS" condition which existed on the date 
hereof, ordinary wear and tear excepted and in the condition permitted by the 
terms of Article XI.

                                 ARTICLE V - CLOSING

    SECTION 5.1. Purchaser hereby authorizes the Title Company to act as the 
settlement agent for purposes of conducting the Closing. Closing of this 
Agreement (the "Closing") shall be held at the office of the Title Company 
which are located at 51 Monroe Street, Penthouse III, Rockville, Maryland 
20850. If all conditions precedent as set forth in this Agreement are fully 
satisfied (except those conditions for the benefit of Purchaser, if any, 
which Purchaser in its sole discretion may waive in writing, and those 
conditions for the benefit of Seller, if any, which Seller in its sole 
discretion may waive in writing), Purchaser and Seller shall make full 
settlement hereunder pursuant to the terms hereof on a date and at a time 
selected by Purchaser, and mutually convenient to both Seller and Purchaser, 
but in no event shall said date be later than fifteen (15) days following the 
expiration date of the Study Period. Purchaser shall give to Seller at least 
five (5) days prior written notice of its proposed date and time of Closing. 
Purchaser acknowledges that Seller's business offices are in Massachusetts, 
and accordingly, Purchaser agrees to use all reasonable efforts to cause the 
Title Company to deliver to Seller for execution the deed of conveyance, the 
settlement statement, and all other documents necessary for the consummation 
of the transactions contemplated by this Agreement, in advance of the 
proposed date of Closing, and, under such circumstances, Closing shall occur 
without the necessity of a formal meeting of both Seller and Purchaser in the 
offices of the Title Company as otherwise described herein. The date of 
Closing is sometimes referred to as the "Closing date" in this Agreement.



                                          8

                        ARTICLE VI - SELLER'S AND PURCHASER'S
                            REPRESENTATIONS AND WARRANTIES

    SECTION 6.1. Seller represents, warrants and covenants to Purchaser that, 
as of the Execution Date:

    (A) Seller is a corporation duly formed, validly existing and in good 
standing under the laws of the state of its incorporation, is in good 
standing and is qualified to do business in the State of Maryland. Seller has 
the authority and power to enter into this Agreement and to consummate the 
transaction provided for herein, and such action will not breach any court 
order, the organizational documents of Seller or other existing agreement or 
agreements to which Seller is a party. No governmental or third party 
approvals or consents are required for Sellers execution and delivery of this 
Agreement, or performance of its obligations hereunder, and Sellers execution 
and performance hereof do not and shall not violate, and are not restricted 
by, any other contractual obligations or any legal requirements to which 
Seller is a party or by which Seller is bound.

    (B) There is no action, suit, proceeding or investigation pending or, to 
Seller's actual knowledge, threatened before any agency, court or other 
governmental authority which relates specifically to Seller, the Property or 
Seller's operation thereof (other than minor property damage and personal 
injury cases in the nature of slip and fall cases which are being handled in 
due course by Seller's insurance carrier, if any). On the Effective Date, 
(but not necessarily on the Closing Date), no such minor property damage or 
personal injury cases exist. If any such minor property damage or personal 
injury cases exist on the Closing Date, Seller shall so advise Purchaser (but 
the existence thereof shall not be a breach of Seller's representations or 
warranties as set forth herein). There are no actions, suits or proceedings 
pending, contemplated or threatened to be initiated by Seller in connection 
with all or any portion of the Property or Seller's ownership, rights, use, 
development or maintenance thereof, including, without limitation, tax 
reduction proceedings; and from and after the Execution Date, Seller shall 
not commence or allow to be commenced on its behalf any action, suit or 
proceeding with respect to all or any portion of the Property without the 
prior written consent of Purchaser, which consent shall not be unreasonably 
withheld, delayed or conditioned. No attachments, execution proceedings, 
assignments for the benefit of creditors, insolvency, bankruptcy, 
reorganization or other proceedings are pending, or, to Seller's actual 
knowledge, threatened, against Seller. In the event any proceeding of the 
character described herein is initiated prior to the Closing, Seller shall 
promptly advise Purchaser in writing.

    (C) There is no condemnation proceeding affecting the Property currently 
pending, Seller has not received notice of any contemplated condemnation 
proceedings nor, to Seller's actual knowledge, is any such proceeding 
threatened.



                                       9

    (D) To Seller's actual knowledge, Seller has obtained all permits, 
licenses and consents necessary to own, operate, develop, use and maintain 
the Property as commercial office buildings. To Seller's actual knowledge, 
all such permits, licenses and consents are, or will be on the Closing Date, 
in full force and effect. The list of documents set forth on EXHIBIT "H" 
attached hereto (collectively, the "Approvals") are the permits, licenses, 
certifications, approvals, consents, and authorizations in the possession of 
Seller which are applicable to its operation of the Property. To Seller's 
actual knowledge, the Approvals are in full force and effect. To Seller's 
actual knowledge, all of the Approvals are transferable to Purchaser without 
the necessity of any approval or consent or additional payment (other than a 
de minimis payment) and no such transfer will affect the validity thereof. 
Seller has not received notice of any failure of the Property to comply with 
any applicable governmental requirements in regard to the use, occupation and 
construction thereof, including, but not limited to, environmental, zoning, 
platting and other land use requirements and Seller has not received notice 
of and has no actual knowledge of any violations or investigations relating 
thereto.

    (E) Seller has not received notice of any default or breach by Seller 
under any covenants, conditions, restrictions, rights-of-way or easements 
which may affect the Property, and, to Seller's actual knowledge, no such 
default or breach now exists.

    (F) To Seller's actual knowledge, there are no presently pending special 
or general assessments against the Property, and no new special or general 
assessments are threatened against the Property.

    (G) To Seller's actual knowledge, all Exhibits hereto are current, 
complete and correct in all material respects.

    (H) Seller has not received notice of any proposed increase in the 
assessed valuation of the Property.

    (I) The actual income and expenses of the Property for (i) the full 
calendar year l996 and (ii) the partial calendar year 1997 are fully, truly 
and accurately set forth in all material respects on EXHIBIT "C" which is 
attached hereto.

    (J) EXHIBIT "D" attached hereto contains a current, correct and complete 
rent roll including a list of all leases (sometimes, "Leases") with tenants 
of the Property as of the Execution Date. Seller has delivered to Purchaser a 
current, correct and complete copy of each of the Leases, including all 
amendments thereto and guarantees thereof. The information contained in 
EXHIBIT "D;)" (as updated by Seller to Purchaser from time to time) is and 
will continue to be current, correct and complete in all material respects. 
Each of the Leases listed in EXHIBIT "D:)" is in full force and effect. To 
Seller's actual



                                          10

knowledge, Seller is not in default under any of the Leases in any material 
respect. Except as otherwise provided in EXHIBIT "D", as of the Execution 
Date (but not as of the date of Closing), none of the tenants under the 
Leases is in default in the payment of any rent under its Lease, or, to 
Seller's actual knowledge, in the performance or observance of any covenant 
or condition to be kept, observed or performed by the tenant under such 
Lease. Except as otherwise provided in EXHIBIT "D)" or in a Lease, none of 
such tenants is or will be entitled to any rent rebate, concession, deduction 
or offset. No tenant has paid any rent, additional rent or other charge for a 
period of more than thirty (30) days in advance, which shall not be adjusted 
by and between Seller and Purchaser at Closing. Seller has no actual 
knowledge of any claims, defenses or counterclaims that would affect payment 
of rent or other sums or performance of any obligations by the tenants under 
the Leases except as described in EXHIBIT "D". Seller has received no notices 
of any failure of Seller to supply any services which Seller is required to 
furnish pursuant to any Lease. Seller has received no notices of any items of 
work, repair, maintenance or construction to be completed by Seller pursuant 
to any Lease for the benefit of any tenant and Seller has no knowledge of any 
such work to be done. Except as set forth on the Exhibit "D", as of the 
Execution Date (but not as of the date of Closing), Seller has received no 
notice from any tenant (i) to cancel any Lease prior to its natural date of 
expiration, (ii) that such tenant is or may become unable or unwilling to 
perform any or all of its obligations under its Lease, whether for financial 
or other reasons, or that an action or proceeding, voluntary or involuntary, 
is pending or threatened against such tenant under any section or sections of 
any bankruptcy or insolvency law, or (iii) that such tenant disputes the base 
rent or escalation rents or the computation of escalation rents pursuant to 
its Lease. Seller has received no notice of any default by the landlord under 
any Lease and has no actual knowledge of any fact or facts which would now or 
with the giving of notice or the passage of time or both be a default under 
the terms thereof, except as otherwise set forth on EXHIBIT "D".

    As of the Closing Date, there will be no brokerage or other leasing 
commissions payable in connection with any of the existing tenants or the 
Leases, or with any new leases or amendments of existing Leases which were 
acquired without Purchaser's prior written consent [which consent shall be 
granted or withheld in the manner set forth in Section 7.1(D)]. Purchaser 
acknowledges that it shall be obligated to pay any brokerage or other leasing 
commissions payable in connection with any new leases for space in the 
Improvements, or any amendments of existing Leases, executed after the 
Execution Date with Purchaser's prior written consent as aforesaid.

    For all purposes of Seller's representations and warranties contained in 
this Section 6.1(J), any reference to "tenant" shall be deemed a reference 
only to BMI (and any references to Leases shall be deemed a reference only to 
the Lease with BMI), unless



                                       11

BTRL is still a tenant of the Property on the Closing Date, in which event 
all such representations and warranties shall apply to BTRL as well as to BMI.

        (K) EXHIBIT "E" attached hereto contains a current, complete and 
correct list and copy of all contracts or agreements ("Service Contracts") to 
which Seller is a party relating to the management, leasing, operation, 
maintenance or repair of the Property in effect on the Execution Date. Except 
as set forth in EXHIBIT "E", all of such Service Contracts may be terminated 
by Seller or the then owner of the Property without cost or penalty (other 
than a de minimis payment) upon no more than thirty (30) days written notice 
without cause. Seller is not in default under any such Service Contracts to 
its actual knowledge.

        (L) All bills and claims for labor and construction performed and 
materials, equipment or services furnished to or for the benefit of the 
Property for all periods prior to the Closing Date which could result in a 
valid mechanic's lien being filed against the Property will be paid in full 
as of the Closing Date, or, if not paid, will be bonded to the reasonable 
satisfaction of Purchaser and the Title Company. As of the Closing Date, 
there will be no mechanic's liens or materialmen's liens (whether or not 
perfected) on the Property.

        (M) To Seller's actual knowledge, except as set forth in EXHIBIT "F" 
attached hereto, (i) no toxic materials, hazardous waste or hazardous 
substance (as these terms are defined in the Resource Conservation and 
Recovery Act of 1976, as amended (42 U.S.C. Section 6901 ET. SEQ.) or in the 
Comprehensive Environmental Response, Compensation, and Liability Act of 
1980, as amended (42 U.S.C. Section 9601 ET. SEQ.)) including, without 
limitation, any asbestos or asbestos-related products or materials and any 
oils, lead, lead based products or materials, petroleum-derived compounds or 
pesticides (hereinafter referred to as the "Hazardous Materials") are located 
on or about the Property, other than commercially reasonable amounts of such 
materials which are used by tenants of the Property in the ordinary conduct 
of their businesses as permitted by their Leases, and oil and gas stored in 
vehicles located on the Property; (ii) the Property has not been used for the 
storage, manufacture or disposal of Hazardous Materials or as a dump site for 
Hazardous Materials; and (iii) Seller has complied with all federal, state 
and local environmental laws and regulations affecting the Property. Further, 
no complaint, order, citation or notice with regard to air emissions, water 
discharges, noise emissions, Hazardous Materials or any other environmental, 
health or safety matters affecting the Property or any portion thereof from 
any person, government or entity has been received by Seller, and to Seller's 
actual knowledge, no such complaint, order, citation, or notice has been 
issued (but not received) by Seller. To Seller's actual knowledge, any 
Hazardous Materials used by tenants of the Property as set forth in 
subsection (i) above, are stored and used on the Property in accordance with 
applicable law pertaining to the hazardous nature of such materials. To


                                         12

Seller's actual knowledge, except as set forth in EXHIBIT "F", the Property 
does not contain any underground tanks for the storage or disposal of 
Hazardous Materials.

        (N) All fixtures, equipment and personal property listed in EXHIBIT 
"B" and included in this sale are, and at Closing will be, owned by Seller 
(except to the extent that such items are consumed or are discarded after 
becoming broken, damaged or obsolete in the ordinary course of Seller's 
operation of the Property), and at Closing all of the foregoing will be free 
and clear of any chattel mortgages, conditional bills of sale, security 
agreements or financing statements and other liens and encumbrances of any 
kind.

        (O) Seller is the legal and equitable owner of the Property, with 
full right to convey the same. Seller has not granted any options or rights 
of first refusal or rights of first offer to third parties to purchase or 
otherwise acquire an interest in the Property (other than extension rights or 
options to renew leasehold interests as may be set forth in the Leases).

        (P) Seller has received no notice of any filing or petition, under 
the United States Bankruptcy Law or any insolvency laws, or any laws for 
composition of indebtedness or for the reorganization of debtors, which 
pertains to Seller, and Seller has filed no such notice or petition.

        (Q) Seller is not a foreign person within the meaning of 42 USCS 
Section 1445(f)(3).

        (R) There are currently in effect such insurance policies as are 
listed on EXHIBIT "I" attached hereto. All premiums due on such insurance 
policies have been paid by Seller and Seller will maintain such insurance 
policies from the Execution Date through the Closing Date or earlier 
termination of this Agreement. Seller has not received and has no actual 
knowledge of any notice or request from any insurance company requesting the 
performance of any repair work or alteration with respect to the Property 
which has not been complied with. Seller has received no notice from any 
insurance company concerning, nor does Seller have actual knowledge of, any 
defects or inadequacies in the Property which, if not corrected, would result 
in the termination of the insurance coverage identified on EXHIBIT "I", or 
increase its cost.

        (S) There are no employees who are employed by Seller in the 
operation, management or maintenance of the Property for whom Purchaser shall 
have any obligation after the Closing Date.

        (T) Seller has not received written notice that any party to any of 
the Property Documents considers a breach or default by Seller to have 
occurred.


                                          13

As used in this Agreement, the term "Seller's actual knowledge" means the 
actual (and not the constructive) current knowledge of Stephen J. DiPalma, 
Chief Financial Officer of Seller, and does not imply any inspection, 
examination or other inquiry undertaken by Seller or said individual to 
determine the accuracy of any representation, warranty or other statement 
made "to Seller's actual knowledge" in this Agreement, or in any of the 
documents to be executed by Seller and delivered to Purchaser at Closing.

    SECTION 6.2. Purchaser represents, warrants and covenants to Seller that, 
as of the Execution Date:

        (A) Purchaser is a corporation duly formed, validly existing and in 
good standing under the laws of the state of its incorporation, and is in 
good standing and qualified to do business in the State of Maryland. 
Purchaser has the authority and power to enter into this Agreement and to 
consummate the transactions provided for herein, and such action will not 
breach any court order, the organizational documents of Purchaser or other 
existing agreement or agreements to which Purchaser is a party.

        (B) This Agreement constitutes the valid and binding obligation of 
Purchaser.

        (C) No governmental or third party approvals or consents are required 
for Purchaser's execution and delivery of this Agreement, or performance of 
its obligations hereunder, and Purchaser's execution and performance hereof 
do not and shall not violate, and are not restricted by, any other 
contractual obligations or any legal requirements to which Purchaser is a 
party or by which Purchaser is bound.

    SECTION 6.3. All of the representations, warranties and covenants of 
Seller contained in this Article VI or elsewhere herein are material 
inducements to Purchaser's execution of this Agreement and to its agreement 
to purchase the Property, and all of the representations, warranties and 
covenants of Purchaser contained in this Article VI or elsewhere herein are 
material inducements to Seller's execution of this Agreement and to its 
agreement to sell the Property. At Closing, Seller and Purchaser each shall 
reconfirm to the other party in writing, by certification in the form which 
is attached hereto as EXHIBIT "L", its representations and warranties made 
herein as of the Closing Date, including any non-material modifications 
thereto which are necessitated by a change of circumstances, and shall 
deliver said written certification to the other party. All representations 
and warranties of both parties hereunder shall be deemed to be continuing 
representations and warranties, and shall continue in force through Closing 
and shall survive the Closing of the sale and purchase of the Property under 
this Agreement for a period of one (1) year from the Closing Date, at which 
time they shall expire and be of no further force or effect. If any 
representations or warranties of Seller are not correct as of the Closing 
Date, then Purchaser at its sole option and discretion may elect to (i) 
terminate this Agreement whereupon the


                                          l4

Deposit shall be promptly returned to Purchaser, and both Seller and 
Purchaser shall perform the obligations required of each of them upon 
a termination of this Agreement as otherwise described herein, after 
which this Agreement shall be null and void, or (ii) waive in writing 
such inaccuracies or nonperformance and proceed hereunder without 
regard thereto, or (iii) institute actions against Seller for specific 
performance or other relief in equity [provided, if said failure of 
such representations and/or warranties to be true is not the result of 
the willful action or inaction of Seller in disregard of its obligations 
to Purchaser as set forth in this Agreement, and if Seller can cause said 
representation or warranty to become true, then Seller shall not be obligated
to perform any work to the Property or to expend any monies other than as 
expressly set forth herein, and Seller shall be obligated only to deliver the 
Property to Purchaser on the Closing Date in the same "AS IS, WHERE IS"
condition which existed on the Execution Date, excepting therefrom changes
in the condition of the Property caused by ordinary wear and tear or as set 
forth in Article XI.] Similarly, if any representations or warranties of 
Purchaser are not correct as of the Closing Date, then Seller at its sole 
option and discretion may elect to proceed in the same manner as Purchaser 
as set forth in subsections (i)-(iii) above.

    SECTION 6.4. Other than as expressly set forth in this Article VI or 
elsewhere in this Agreement, Purchaser shall have no claim for any damage or 
remedy by reason of the existence or nonexistence of (i) any fact not 
represented herein, or (ii) any condition of the Property, the nature of any 
tenancy or the terms of any Leases, or any other circumstance surrounding the 
Property or its sale by Seller to Purchaser, which is not specifically 
addressed by this Agreement.

                 ARTICLE VII - SELLER'S OBLIGATIONS PENDING CLOSING

    SECTION 7.1. During the continuance of this Agreement, until the Closing 
Date, Seller covenants to perform the following obligations:

        (A) Seller shall continue to operate the Property as commercial 
office buildings in the same manner as presently operated. In this respect, 
Seller shall (1) continue to repair and maintain the Property (including the 
repair, maintenance and, if necessary, the replacement of equipment, 
furniture, furnishings, fixtures and appliances) in the same manner as 
presently repaired and maintained, in all material respects (but subject to 
the provisions of Section 4.3); (2) not knowingly violate any lawful order or 
directive of a governmental agency with respect to the Property; (3) manage 
the Property by collecting rents and otherwise enforcing the Leases and 
rental agreements of the various tenants; (4) perform all obligations 
required of it pursuant to the Service Contracts; and (5) maintain, keep in 
effect, and pay the premiums for the insurance on the Property which is in 
effect on the Execution Date.



                                       15

        (B) Seller will not directly or indirectly sell, assign, convey or 
create any right, title, or interest in the Property to any third party, or 
enter into any agreement to do any of the foregoing, without first acquiring 
the prior written consent of Purchaser thereto, as Purchaser shall determine 
in its sole discretion (except as otherwise expressly provided herein). 
Except for the Permitted Exceptions, Seller will not create or permit to 
exist any lien, encumbrance, or charge on the Property, without discharging 
the same at or prior to Closing (except as otherwise expressly provided 
herein).

        (C) Seller will not enter into any new contracts, or amend or 
terminate any existing Service Contracts which may not be canceled on thirty 
(30) days' notice, or permit any major management or operational changes 
relating to the management, leasing, operation, maintenance or repair of the 
Property, without Purchaser's prior written approval which approval shall not 
be unreasonably withheld, conditioned or delayed.

        (D) Seller will not enter into any new leases, or amend or terminate 
any existing Leases between the Execution Date and the expiration date of the 
Study Period without Purchaser's prior written consent, which consent shall 
not be unreasonably withheld, conditioned or delayed; Seller will not enter 
into any new leases, or amend or terminate any existing Leases between the 
expiration date of the Study Period and the Closing Date without Purchaser's 
prior written consent, which consent may be granted, conditioned or withheld 
as Purchaser shall determine in its sole discretion. Purchaser shall be 
deemed to have acted unreasonably in not approving a new lease or an 
amendment of an existing Lease between the Execution Date and the expiration 
date of the Study Period if the proposed use of the premises is for lab 
and/or related office purposes, and the rent to be paid by the proposed 
tenant is consistent with the fair market rental value of said premises.

        (E) Seller shall promptly notify Purchaser of any change in any 
condition with respect to the Property or any portion thereof or of any event 
or circumstance of which Seller acquires actual knowledge subsequent to the 
Execution Date which (a) materially, adversely affects the Property or any 
portion thereof or the use or operation of the Property or any portion 
thereof, (b) makes any representation or warranty of Seller to Purchaser 
under this Agreement untrue or misleading, or (c) makes any covenant or 
agreement of Seller under this Agreement incapable or unlikely of being 
performed, it being expressly understood that Seller's obligation to provide 
information to Purchaser under this Section 7.1 shall in no way relieve 
Seller of any liability for a breach by Seller of any of its representations, 
warranties, covenants or agreements under this Agreement.

        (F) Seller shall have the right to maintain the Property on the 
market, and to commence and/or continue any and all negotiations with any 
other



                                          16

prospective optionees or purchasers of the Property, until such time as the 
Study Period has expired and the parties are proceeding to Closing in 
accordance with the terms of this Agreement. At all times after the Execution 
Date, Seller shall advise Purchaser of the status of any negotiations with 
potential tenants at the Property.

                     ARTICLE VIII - CLOSING REQUIREMENTS

   SECTION 8.1. At Closing, Seller shall do the following:

        (A) Deliver to Purchaser all Seller's Documents including the 
original Leases (to the extent said original instruments are in the 
possession or control of Seller, otherwise copies shall be delivered to 
Purchaser), to the extent not previously delivered pursuant to Article III 
above;

        (B) Execute and deliver to Purchaser an assignment of all Service 
Contracts;

        (C) Execute and deliver to the Title Company an affidavit in form and 
substance satisfactory to the Title Company and consistent with customary 
practices in Montgomery County, Maryland, permitting the Title Company to 
delete from Purchaser's title policy exceptions for mechanics' liens and 
parties in possession (other than tenants under recorded leases, if any, and 
specifically identified tenants then occupying space in the Property under 
unrecorded leases);

        (D) Execute and deliver to Purchaser and the Title Company a sworn 
statement that Seller is not a "foreign person" and containing such other 
information as may be required by Section 1445(b)(2) of the Internal Revenue 
Code, and regulations thereunder;

        (E) Execute and deliver to Purchaser an assignment of all Leases, and 
assign and deliver any deposits related thereto in the form attached hereto 
as EXHIBIT "M" [with security and/or tenant deposits being equal to the 
deposits made by current tenants, accrued interest, if any, earned by tenants 
in accordance with their respective Leases and local law, and deposit refunds 
plus interest due, but not yet paid, less any monies expended by Seller (or 
its predecessors-in-interest, as landlord) from said security and/or tenant 
deposits to cure defaults by tenants of the Property];

        (F) Execute and deliver to Purchaser an assignment of (i) the Project 
Plans, and (ii) all licenses, franchises, permits and contract rights 
relating to the operation of the Property, to the extent the same are 
assignable;




                                       17

        (G) Execute and deliver to Purchaser (i) a good and sufficient bill 
of sale in the form attached hereto as EXHIBIT "N" conveying to Purchaser 
good title to all personal property described on EXHIBIT "B";

        (H) Execute and deliver to Purchaser a certification that all 
representations and warranties set forth in Section 6.1 are true and correct 
on the Closing Date (as same may be modified in a non-material manner 
resulting from a change in circumstances);

        (I) Such proof of Seller's authority and authorization to enter into 
this Agreement and the transactions contemplated hereby, and such proof of 
the power and authority of the individual(s) executing any instruments, 
documents or certificates on behalf of Seller as may be reasonably required 
by Title Company, Purchaser or the New Lenders;

        (J) Such other documents and instruments, signed and properly 
acknowledged by Seller, if appropriate, as may be reasonably required by 
Purchaser, Escrow Agent, the New Lenders or otherwise in order to effectuate 
the provisions of this Agreement and the Closing of the transactions 
contemplated herein (but only to the extent that any such document does not 
enlarge or extend the obligations of Seller as provided in this Agreement); 
and

        (K) Seller shall deliver possession of the Property to Purchaser upon 
the Closing, subject to the rights of tenants under the Leases. Further, 
Seller hereby covenants and agrees to deliver to Purchaser, on or prior to 
the Closing, the following items:

            (a)  Originals of the Approvals (to the extent same are in
                 Seller's possession or under its control);

            (b)  The Intangible Property, including, without limitation,
                 the original Seller's Documents (to the extent same are
                 in Seller's possession or under its control and have not
                 been previously delivered); and

            (c)  The Personal Property, including, without limitation, all
                 keys, pass cards, remote controls, security codes,
                 computer software and other devices relating to access
                 to the Improvements.



                                       18

        (L) Execute and/or deliver such other documents as Seller and 
Purchaser may have agreed for Seller to deliver at Closing.

        (M) Execute and deliver to Purchaser a Special Warranty Deed to the 
Land and Improvements in the form attached hereto as EXHIBIT "J".

    SECTION 8.2. At Closing, Purchaser shall deliver the Purchase Price to 
Seller, and shall do the following:

        (A) Execute and deliver to Seller an assumption of all Seller's 
obligations from and after the Closing Date set forth in the Service 
Contracts which are assigned by Seller to Purchaser pursuant to 
Section 8.1(B) hereof;

        (B) Execute and deliver to Seller an assumption of all Seller's 
obligations from and after the Closing Date set forth in Leases which are 
assigned by Seller to Purchaser pursuant to Section 8.1(E) hereof 
(including, without limitation, all obligations relating to deposits held by 
landlord under said Leases and delivered by Seller to Purchaser);

        (C) Deliver to Seller and the Title Company evidence reasonably 
satisfactory to Seller and the Title Company that (i) Purchaser is duly 
formed and validly existing in the state of its formation and is in good 
standing and qualified to do business under the laws of the State of 
Maryland, and (ii) Purchaser has the authority and power to enter into this 
Agreement and to consummate the transaction provided for herein, (iii) the 
consummation of the transaction provided for herein will not breach the 
organizational documents of Purchaser, and (iv) the individuals executing all 
documents in connection herewith on behalf of Purchaser have the authority 
and power so to do;

        (D) Execute and deliver to Seller a certification that all 
representations and warranties set forth in Section 6.2 are true and correct 
on the Closing Date;

        (E) Execute and/or deliver such other documents as Seller and 
Purchaser may have agreed for Purchaser to deliver at Closing;

        (F) Such proof of Purchaser's authority and authorization to enter 
into this Agreement and the transactions contemplated hereby, and such proof 
of the power and authority of the individual(s) executing any instruments, 
documents or certificates on behalf of Purchaser as may be reasonably 
required by Title Company or Seller; and



                                       19

        (G) Such other documents and instruments, signed and properly 
acknowledged by Purchaser, if appropriate, as may be reasonably required by 
Seller, Escrow Agent, or otherwise in order to effectuate the provisions of 
this Agreement and the Closing of the transactions contemplated herein (but 
only to the extent that any such document does not enlarge or extend the 
obligations of Purchaser as provided in this Agreement).

    The delivery to the Title Company of the Purchase Price, the executed 
deed of conveyance, bill of sale, assignment of the Leases and security 
deposits, assignment of the Service Contracts, and all other documents and 
instruments required to be delivered by either party to the other by the 
terms of this Agreement shall be deemed to be a good and sufficient tender of 
performance of the terms hereof.

          ARTICLE IX - CONDITIONS TO OBLIGATIONS OF PURCHASER
                          AND SELLER TO CLOSE

    SECTION 9.1. The obligations of Purchaser to close hereunder shall be 
conditioned upon the fulfillment of the following conditions at or prior to 
Closing:

        (A) Seller shall have performed all agreements, undertakings and 
obligations and complied with all conditions required by this Agreement to be 
performed and/or complied with by Seller in all material respects.

        (B) All representations and warranties made by Seller set forth in 
Article VI shall be true and correct on the Closing Date, in all material 
respects, as if made on and as of the Closing Date.

        (C) No action or proceeding shall have been commenced by or against 
Seller under the federal bankruptcy code or any state law for the relief of 
debtors or for the enforcement of the rights of creditors and no attachment, 
execution, lien or levy shall have attached to or been issued with respect to 
the Property or any portion thereof.

        (D) BTRL is no longer in possession of any portion of the Property, 
or alternatively, Seller shall have performed its obligations to Purchaser to 
acquire an Estoppel Certificate from BTRL prior to the expiration of the 
Study Period in conformance with the requirements of Section 3.3 (the 
contents of which Purchaser shall have approved or disapproved in connection 
with its determination whether to proceed to Closing or to terminate the 
Agreement prior to the expiration of the Study Period).

        (E) No damage, destruction or loss to the Property in excess of 
$100,000.00, whether or not covered by insurance, shall have occurred and not 
be repaired prior to the Closing Date.



                                          20

    In the event that any of the conditions set forth above in this Section 
9.1 have not been fulfilled in all material respects on the Closing Date, 
Purchaser shall have the right, at its option, to terminate this Agreement by 
giving written notice to Seller, in which event Purchaser shall return the 
Seller's Documents to Seller and repair any damage to the Property caused by 
its studies and investigations, the Deposit shall be returned to Purchaser 
and the parties hereto shall be relieved of all obligations hereunder, except 
that the foregoing shall not relieve Seller of any liability to Purchaser for 
the breach of any representation or warranty set forth in this Agreement in 
the manner set forth in Section 6.3, or for a default in the performance of 
its obligations set forth in this Agreement in the manner set forth in 
Article XII.

    SECTION 9.2. The obligations of Seller to close hereunder shall be 
conditioned upon the fulfillment of the following conditions at or 
prior to Closing:

         (A) Purchaser shall have performed all agreements, undertakings 
     and obligations and complied with all conditions required by this 
     Agreement to be performed and/or complied with by Purchaser in all 
     material respects.

         (B) All representations and warranties made by Purchaser set forth in 
     Article VI shall be true and correct on the Closing Date, in all material 
     respects, as if made on and as of the Closing Date.

    In the event that any of the conditions set forth above in this Section 
9.2 have not been fulfilled in all material respects on the Closing Date, 
Seller shall have the right, at its option, to terminate this Agreement by 
giving written notice to Purchaser, in which event the Deposit shall be 
returned to Purchaser and the parties hereto shall be relieved of all 
obligations hereunder, except that the foregoing shall not relieve Purchaser 
of any liability to Seller for the breach of any representation or warranty 
set forth in this Agreement in the manner set forth in Section 6.3 hereof, or 
for a default in the performance of its obligations set forth in this 
Agreement in the manner set forth in Article XII.

    SECTION 9.3. Either party shall have the right at its option to waive in 
writing any conditions of this Agreement which are included for its benefit, 
and to proceed hereunder without regard to any nonperformance or 
non-satisfaction thereof.

                ARTICLE X - PRORATION AND ADJUSTMENTS; CLOSING COSTS

    SECTION 10.1. All items of income and expense including, but not limited to
water and sewer connection charges, rents and other payments under the Leases,
water and sewer charges, charges for electricity, gas, fuel oil, telephone, and
other utilities and license fees (of transferable licenses), and charges under
all Service Contracts in effect on the Closing Date shall be adjusted and
apportioned between the parties hereto as of 11:59 P.M.




                                          21

on the day immediately preceding the Closing, and the net amount thereof 
shall be added to or deducted from, as the case may be, the amount of the 
Purchase Price to be paid at the time of Closing. Taxes, general and special, 
are to be adjusted as aforesaid (and assumed by Purchaser as of the Closing 
Date) according to the certificate of taxes issued by the appropriate 
governmental taxing authorities having jurisdiction of the Property, 
including, without limitation, assessments for any improvements which are 
levied or assessed prior to the Closing Date. In making the adjustments 
required by this Section, Seller shall receive credit for all prepaid 
expenses and similar items that are due on or after the Closing Date, and 
Seller shall be charged with any unpaid charges for the period prior to the 
Closing Date. In adjusting for uncollected rents, no adjustment shall be made 
in Seller's favor for rents which are accrued or are unpaid as of the time of 
Closing, but Purchaser shall make reasonable efforts (without being obligated 
to incur any costs or expenses which are not reimbursable by Seller) to 
collect any arrearages of rent existing on the Closing Date, and shall pay 
Seller such accrued and unpaid rents as and when collected by Purchaser after 
Closing (less reasonable expenses of collection thereof), it being understood 
that Purchaser shall not be deemed to have collected any such arrearages 
attributable to the period prior to the Closing Date until such time as the 
tenant(s) from whom the late rent is collected shall become current in the 
payment of all rents accruing after the Closing Date. Notwithstanding the 
foregoing, Seller shall have the right after the Closing Date to commence an 
action against any tenant to collect amounts due Seller from any such tenant 
with respect to periods of time prior to the Closing Date, provided that 
Seller shall not be entitled to dispossess any such tenant as a result of 
such action.

    On the Closing Date, Purchaser shall be fully credited for (i) 
reimbursement expenses and other sums owed by Seller to tenants for work 
which occurred prior to the Closing Date which Seller is obligated to 
reimburse tenants, or for work to be performed or allowances to be granted to 
any tenants upon or after the Closing Date pursuant to any Leases in 
existence as of the Execution Date (provided that Purchaser agrees to pay for 
any such work to be performed or allowances to be granted to any tenants 
under leases approved by Purchaser between the Execution Date and the Closing 
Date), (ii) any commissions or brokerage fees payable upon or after the 
Closing Date in connection with any Leases in existence as of the Execution 
Date (provided that Purchaser agrees to pay for any such commissions or 
brokerage fees under leases approved by Purchaser between the Execution Date 
and the Closing Date), and (iii) rentals already received by Seller 
attributable to periods after the Closing Date. If real estate tax bills have 
not yet been received by Seller by the Closing Date or if supplemental taxes 
are assessed (or taxes are reduced) after the Closing for the period prior to 
the Closing, the parties shall make any necessary adjustment after the 
Closing by cash payment to the party entitled thereto so that Seller shall 
have borne all taxes, including all supplemental taxes, allocable to the 
period prior to the Closing and Purchaser shall bear all taxes, including all 
supplemental taxes, allocable to the period after the Closing. If any 
expenses attributable to the Property and allocable to the period prior to 
the Closing are discovered or billed after the



                                          22

Closing, then, if and only to the extent that Seller is obligated for the 
payment of said expenses pursuant to the terms of this Agreement, the parties 
shall make any necessary adjustment after the Closing by cash payment to the 
party entitled thereto so that Seller shall have borne all expenses allocable 
to the period prior to the Closing, and Purchaser shall have borne all 
expenses allocable to the period on and after the date of Closing. The 
provisions of this Section 9.2 shall survive the Closing for a period of one 
(1) year.

    Not later than three (3) Business Days prior to the Closing, Escrow Agent 
shall deliver to each of the parties for their review and approval a 
preliminary closing statement (the "Preliminary Closing Statement") based on 
an income expense statement prepared by Seller, approved by Purchaser, and 
delivered to Escrow Agent prior to said date, setting forth (i) the proration 
amounts allocable to each of the parties pursuant to this Section 10.1 and 
(ii) the Closing Costs allocable to each of the parties pursuant to Section 
10.4 hereof. Based on each of the party's comments, if any, regarding the 
Preliminary Closing Statement, Escrow Agent shall revise the Preliminary 
Closing Statement and deliver a final, signed version of a closing statement 
to each of the parties at the Closing (the "Closing Statement").

    SECTION 10.2 Seller represents that EXHIBIT "D" sets forth a complete 
list of all security deposits and other deposits (and the interest thereon, 
if any) held by Seller under the Leases as of the Execution Date, to the 
extent not theretofore lawfully applied to cure a default by any tenants in 
accordance with the Leases (hereinafter collectively referred to as the 
"Security Deposits"). At the Closing, (i) the Purchase Price shall be 
adjusted to the credit of Purchaser in an amount equal to the total of the 
Security Deposits as of the Closing Date, and (ii) Seller shall assign in 
writing to Purchaser all of Seller's right, title and interest in and to the 
Security Deposits, and Purchaser shall assume in writing Seller's obligation 
for the refund or other proper application thereof as set forth in Sections 
8.1 and 8.2 respectively.

    SECTION 10.3. At Closing, the net adjustment, if in favor of Seller, 
shall be paid to Seller in the same manner as the Purchase Price or, if in 
favor of Purchaser, shall be paid by setoff against the Purchase Price.

    SECTION 10.4. All costs associated with (i) the issuance of an owner's 
title insurance policy (without issuance of any endorsements to standard 
coverage), (ii) the preparation of the Survey, and (iii) State, county and 
municipal recordation tax and transfer tax with respect to the deed of 
conveyance of the Property to Purchaser shall be borne and paid one-half 
(1/2) by Seller and one-half (1/2) by Purchaser. Seller and Purchaser shall 
pay, respectively, the fees and expenses of its own attorneys in connection 
with negotiation and settlement of this Agreement. Purchaser shall pay any 
and all other fees and expenses associated with Closing unless Seller is 
otherwise expressly obligated by the terms of this Agreement to pay same, 
including, without limitation the costs of issuance of a mortgagee's



                                          23

title insurance policy and any endorsements to standard title insurance 
coverage provided to either Purchaser or its mortgagee, and the cost of the 
UCC Searches. If, on the Closing Date, title to the Property is not in the 
form required by this Agreement and the cause thereof is within the 
reasonable control of Seller, and such matters are not timely addressed by 
and at the sole expense of Seller in the manner required hereby, then, if 
Purchaser terminates this Agreement by reason of any such title matters, 
Seller will promptly pay all costs incurred for the title examination and 
survey of the Property in an amount not to exceed Eight Thousand Eight 
Hundred Dollars ($8,800.00).

                      ARTICLE XI - CASUALTY LOSS; CONDEMNATION

    SECTION 11.1. If, prior to Closing, all or any portion of the Property is 
taken by condemnation or eminent domain, (or is the subject of a pending 
taking which has not been consummated but only to the extent such a taking 
would materially interfere with the use and operation of the Property by 
Purchaser), Seller shall so notify Purchaser within three (3) days after the 
occurrence of such event. In such event, Purchaser shall have the option to 
terminate this Agreement upon written notice to Seller given not later than 
fifteen (15) days after receipt of such notice from Seller. If Purchaser 
elects to terminate this Agreement under Article IX or Article XI, then the 
Seller's Documents will be returned to Seller, any damage to the Property 
caused by Purchaser studies thereon shall be repaired by Purchaser, and the 
Deposit shall be returned to Purchaser and neither party shall have any 
further liability to the other (except as expressly provided herein). If 
Purchaser does not elect to terminate this Agreement as aforesaid, it shall 
accept title to the Property without any abatement of the Purchase Price 
whatsoever, in which event, at the Closing, all of the condemnation award, or 
right to such condemnation award, which have not been applied on account of 
any reasonably necessary repairs or restorations, shall be assigned by Seller 
to Purchaser and any moneys theretofore received by Seller in connection with 
such condemnation shall be paid over to Purchaser, except for rent loss 
coverage for periods prior to the Closing Date and proceeds used for 
reasonably necessary restorations or repairs.

    SECTION 11.2. Prior to the Closing and notwithstanding the pendency of 
this Agreement, the entire risk of loss or damage by earthquake, flood, 
landslide, fire, hurricane, tornado or other casualty shall be borne and 
assumed by Seller in the manner set forth herein. If prior to Closing any 
part of the Property is damaged or destroyed by earthquake, flood, landslide, 
fire, hurricane, tornado or other casualty, Seller shall promptly notify 
Purchaser of such fact. In such event, and only in the event that the cost of 
restorations or repairs of said damage exceeds $100,000.00, Purchaser shall 
have the option to terminate this Agreement upon written notice to Seller 
given not later than fifteen (15) days after receipt of any such notice from 
Seller. If Purchaser does not elect to terminate this Agreement, Seller shall 
assign and turn over, and Purchaser shall be entitled to receive and keep, 
all insurance proceeds payable with respect to such destruction (which shall 
then be repaired or not at Purchaser's option and cost), plus Seller shall 
pay over to Purchaser at Closing an



                                          24

amount equal to the deductible amount with respect to the casualty insurance 
(except for rent loss coverage for periods prior to the Closing Date, and 
insurance proceeds and the deductible amount applied by Seller for reasonably 
necessary restorations or repairs) and the parties shall proceed to Closing 
pursuant to the terms hereof without modification of the terms of this 
Agreement and without any reduction in the Purchase Price. If Purchaser does 
not elect to terminate this Agreement by reason of any casualty, Purchaser 
shall have the right to participate in any adjustment of the insurance claim. 
Purchaser shall accept title to the Property without any abatement of the 
Purchase Price whatsoever, in which event, at the Closing, the insurance 
proceeds or right to such proceeds shall be assigned by Seller to Purchaser 
and any moneys theretofore received by Seller in connection with such fire or 
other casualty shall be paid over to Purchaser, except for rent loss coverage 
for periods prior to the Closing Date and proceeds used by Seller for 
reasonably necessary restorations or repairs incurred prior to the Closing 
Date. At Closing, Purchaser shall be entitled to a credit of Two Thousand 
Five Hundred Dollars ($2,500.00) for Seller's deductible under its casualty 
insurance policy, less any amount of expenses incurred by Seller prior to the 
Closing Date for reasonably necessary restorations or repairs of the 
Property. Seller represents to Purchaser that the deductible under its 
casualty insurance policy covering the Improvements is Two Thousand Five 
Hundred Dollars ($2,500.00).

                   ARTICLE XII - SELLER'S AND PURCHASER'S REMEDIES

    SECTION 12.1. IN THE EVENT THAT THIS TRANSACTION FAILS TO CLOSE AS A 
RESULT OF THE DEFAULT OF PURCHASER IN THE PERFORMANCE OF ITS OBLIGATIONS 
UNDER THIS AGREEMENT, PURCHASER AND SELLER AGREE THAT SELLER'S ACTUAL DAMAGES 
WOULD BE IMPRACTICABLE OR EXTREMELY DIFFICULT TO FIX. THE PARTIES THEREFORE 
AGREE THAT IN THE EVENT THAT THIS TRANSACTION FAILS TO CLOSE AS A RESULT OF 
THE DEFAULT OF PURCHASER IN THE PERFORMANCE OF ITS OBLIGATIONS HEREUNDER AND 
SELLER IS READY, WILLING AND ABLE TO PERFORM ITS OBLIGATIONS HEREUNDER, 
SELLER, AS SELLER'S SOLE AND EXCLUSIVE REMEDY, IS ENTITLED TO LIQUIDATED 
DAMAGES IN THE AMOUNT OF THE DEPOSIT (INCLUSIVE OF INTEREST EARNED THEREON) 
THEN HELD BY ESCROW AGENT. IN THE EVENT THIS TRANSACTION FAILS TO CLOSE AS A 
RESULT OF PURCHASER'S DEFAULT AND SELLER IS READY, WILLING AND ABLE TO 
PERFORM ITS OBLIGATIONS HEREUNDER, THEN (1) ESCROW AGENT SHALL, AND IS HEREBY 
AUTHORIZED AND INSTRUCTED TO, RETURN PROMPTLY TO PURCHASER AND SELLER ALL 
DOCUMENTS AND INSTRUMENTS TO THE PARTIES WHO DEPOSITED THE SAME, (2) ESCROW 
AGENT SHALL DELIVER THE DEPOSIT (INCLUSIVE OF INTEREST EARNED THEREON) THEN 
HELD BY ESCROW AGENT TO SELLER PURSUANT TO SELLER'S INSTRUCTIONS, AND THE 
SAME SHALL BE THE FULL, AGREED AND LIQUIDATED DAMAGES, AND (3) THIS AGREEMENT 
AND THE RIGHTS AND



                                          25

OBLIGATIONS OF PURCHASER AND SELLER HEREUNDER AND THE ESCROW CREATED HEREBY 
SHALL TERMINATE UPON THE COMPLETION OF THE OBLIGATIONS SET FORTH IN CLAUSES 
(1) AND (2) ABOVE. SELLER AND PURCHASER ACKNOWLEDGE THAT THEY HAVE READ AND 
UNDERSTAND THE PROVISIONS OF THIS SECTION 12.1, AND BY THEIR INITIALS 
IMMEDIATELY BELOW AGREE TO BE BOUND BY ITS TERMS.

/s/                            /s/ 
_____________________          _____________________________
Seller's Initials              Purchaser's initials


    SECTION 12.2. If Seller defaults hereunder prior to Closing, and provided 
Purchaser is not in default hereunder, then Purchaser shall have the right 
either (i) to terminate this Agreement by giving written notice to Seller, 
whereupon Escrow Agent shall return the Deposit to Purchaser, this Agreement 
shall be null and void and the parties shall have no further liability to one 
another; or (ii) in lieu of terminating this Agreement, to pursue any remedy 
available to Purchaser hereunder, at law or in equity, including specific 
performance of this Agreement, without any reduction in the Purchase Price; 
provided, however, unless said failure by Seller is the result of the willful 
action or inaction of Seller in disregard of its obligations to Purchaser as 
set forth in this Agreement, Seller shall not be obligated to perform any 
work to the Property or to expend any monies other than as expressly set 
forth herein, and Seller shall be obligated only to deliver the Property to 
Purchaser on the Closing Date in the same "AS IS, WHERE IS" condition which 
existed on the Execution Date, and subject further to any changes in the 
condition of the Property caused by ordinary wear and tear or as set forth in 
Article XI.

                            ARTICLE XIII - INDEMNIFICATION

    SECTION 13.1 Except for and subject to any limitation expressly set forth 
herein, Seller hereby agrees to indemnify, defend and hold harmless Purchaser 
from and against any and all claims, demands, liabilities, costs, expenses, 
penalties, damages and losses, including, without limitation, reasonable 
attorneys' fees and court costs, resulting from or in any way relating to 
Seller's ownership, maintenance, operation or leasing of the Property prior 
to the Closing Date, or from business done, transactions entered into or 
other events occurring prior to the Closing Date with respect to the 
ownership, management, operation, maintenance and repair of the Property, 
other than the debts, liabilities, claims and obligations which are being 
adjusted between Seller and Purchaser as of the Closing Date pursuant to this 
Agreement. Seller shall do, execute and deliver, or shall cause to be done, 
executed and delivered, all such further acts and instruments which Purchaser 
may reasonably request in order to more fully effectuate the indemnification 
provided for in this Agreement. The provisions of this Section 13.1 shall 
survive the Closing for a period of one (1) year from the Closing Date.



                                          26

    SECTION 13.2 Except for and subject to any limitation expressly set forth 
herein, Purchaser hereby agrees to indemnify, defend and hold harmless Seller 
from and against any and all claims, demands, liabilities, costs, expenses, 
penalties, damages and losses, including, without limitation, reasonable 
attorneys' fees and court costs, resulting from or in any way relating to 
Purchaser's ownership, maintenance, operation or leasing of the Property on 
or after the Closing Date, or from business done, transactions entered into 
or other events occurring on or after the Closing Date with respect to the 
ownership, management, operation, maintenance and repair of the Property, 
other than the debts, liabilities, claims and obligations which are being 
adjusted between Seller and Purchaser as of the Closing Date. Purchaser shall 
do, execute and deliver, or shall cause to be done, executed and delivered, 
all such further acts and instruments which Seller may reasonably request in 
order to more fully effectuate the indemnification provided for in this 
Agreement. The provisions of this Section 13.2 shall survive the Closing for 
a period of one (1) year from the Closing Date.                               

                             ARTICLE XIV - AGENCY

    SECTION 14.1 Seller and Purchaser each represents and warrants to the 
other that it has not dealt with any real estate broker, agent, or finder, 
other than Scheer Partners, Inc. and CB Commercial Real Estate Group, Inc. 
(together, the "Brokers") in connection with this Agreement or the 
transactions contemplated by this Agreement. Seller represents and warrants 
to Purchaser that it shall pay all commissions, fees, and other payments due 
to the Brokers, as a result of the transactions contemplated by this 
Agreement, pursuant to a separate written agreement executed by and between 
said parties. Seller and Purchaser shall mutually indemnify and defend the 
other against any costs, claims or expenses, including reasonable attorney's 
fees, arising out of the breach on their respective part of any of their 
above representations in this paragraph. The obligations of Seller and 
Purchaser set forth above shall survive the Closing and the execution and 
delivery of the deed and shall not be merged therein for a period of one (1) 
year from the Closing Date.

                             ARTICLE XV - CONFIDENTIALITY

    SECTION 15.1 Purchaser agrees that until the Closing, except as otherwise 
provided herein or required by law and except for the exercise by Purchaser 
of any remedy hereunder, Purchaser shall (a) keep confidential the pendency 
of this transaction, the documents and information supplied by Seller to 
Purchaser and all studies and reports obtained by Purchaser as part of its 
due diligence investigations of Seller and the Property, (b) disclose such 
information only to Purchaser's agents, employees, contractors, consultants 
or attorneys, as well as lenders (if any), investment bankers, venture 
capital groups, investors and title company personnel, with a need to know in 
connection with Purchaser's review and consideration of the Property, 
provided that Purchaser shall inform all persons receiving such information 
from Purchaser of the confidentiality requirement and (to the extent within


                                         27

Purchaser's control) cause such confidence to be maintained, and (c) upon the 
termination of this Agreement prior to the Closing, return promptly to Seller 
all Seller's Documents and all other documents and materials supplied by 
Seller. Disclosure of information by Purchaser shall not be prohibited if 
that disclosure is of information that is or becomes a matter of public 
record or public knowledge as a result of the Closing of this transaction or 
from sources other than Purchaser or its agents, employees, contractors, 
consultants or attorneys.

    SECTION 15.2. Seller agrees that both prior to and after the Closing, 
except as otherwise provided herein or required by law, and except for the 
exercise by Seller of any remedy hereunder, Seller shall (a) keep 
confidential the pendency of this transaction with Purchaser and the identity 
of Purchaser and the relationship between Purchaser and the entity to which 
Purchaser may assign this Agreement or which Purchaser designates as the 
party to whom Seller shall convey the property at the Closing, and (b) 
disclose such information only to Seller's agents, employees, contractors, 
consultants or attorneys, as well as title company personnel, with a need to 
know such information in connection with effecting this transaction, provided 
that Seller shall inform all such persons receiving such confidential 
information from Seller of the confidentiality requirement and (to the extent 
within Seller's control) cause such confidence to be maintained. Disclosure 
of the pendency of this transaction by Seller shall not be prohibited if that 
disclosure is of information that is or becomes a matter of public record or 
public knowledge as a result of the Closing of this transaction or from 
sources other than Seller or its agents, employees, contractors, consultants 
or attorneys.

                             ARTICLE XVI - MISCELLANEOUS

       SECTION 16.1. APPLICABLE LAW.

    This Agreement shall be construed in accordance with and governed by the
laws of the State of Maryland.

       SECTION 16.2. INTEGRATION; SURVIVAL.

    This Agreement constitutes the entire agreement between Seller and 
Purchaser pertaining to the subject matter hereof and supersedes all prior 
agreements and understandings pertaining thereto. No covenant, representation 
or condition not expressed in this Agreement shall affect or be deemed to 
interpret, change or restrict the express provisions hereof. Except as 
otherwise expressly set forth herein, the rights, powers, privileges, duties, 
obligations, commitments, representations and warranties set forth herein 
shall survive the Closing and the execution and delivery of the deed and 
shall not be merged therein for a period of one (1) year from the Closing 
Date.



                                          28
       SECTION 16.3. AMENDMENT.

    This Agreement may be modified or amended only with the written approval 
of Seller and Purchaser.

       SECTION 16.4. WAIVER.

    No failure by Seller or Purchaser to insist upon the strict performance 
of any covenant, duty, agreement, or condition of this Agreement or to 
exercise any right or remedy consequent upon a breach thereof shall 
constitute a waiver of any such breach or of such or any other covenant, 
agreement, term or condition. No waiver shall affect or alter the remainder 
of this Agreement, but each and every covenant, agreement, term and condition 
hereof shall continue in full force and effect with respect to any other then 
existing or subsequent breach.

       SECTION 16.5. COUNTERPARTS.

    This Agreement may be executed in counterparts, all of which taken 
together shall constitute one agreement binding on all the parties 
notwithstanding that all the parties are not signatories to the original or 
the same counterpart. Each party shall become bound by this Agreement 
immediately upon affixing its signature hereto, independently of the 
signature of any other party. The parties agree that this Agreement (and any 
subsequent agreement of modification or amendment thereto) may be transmitted 
between them by facsimile machine. The parties intend that faxed signatures 
constitute original signatures and that a faxed copy of the Agreement 
containing the signatures (original or faxed) of all the parties is binding 
on the parties.

       SECTION 16.6. NOTICES.

    All notices hereunder shall be in writing and shall be delivered by hand 
or overnight delivery service or, if mailed, sent by United States registered 
or certified mail, postage prepaid, return receipt requested, addressed to 
the appropriate party at its address set forth below, or at such other 
address as such parties shall have last designated by written notice to the 
other. Notices, demands, consents, approvals, and other communications shall 
be deemed given on the second (2nd) business day after being postmarked, if 
sent by mail, or on the date when received by the party to whom it is 
addressed (or the date on which delivery is refused, if attempted), if 
delivered by hand or by overnight delivery service. Seller or Purchaser each 
shall have the right to send any and all notices by electronic facsimile 
transmission ("Fax") to a party at the receiving number set forth below each 
party's name in this Section 16.6, as well as by sending such notices by 
another means of delivery as set forth herein. Any such notices transmitted 
by Fax shall be deemed given on the date of completion of the Fax (as 
evidenced by the telecopier confirmation sheet of the




                                          29

sender) provided that such Fax is confirmed within two (2) business days by a 
duplicate notice sent in a manner otherwise provided herein.

    To Seller:          AQUILA BIOPHARMACEUTICALS, INC.
                        365 Plantation Street
                        Worcester, Massachusetts 01605
                        Attention: Stephen DiPalma
                        Telephone: (508) 797-5777, ext. 513
                        Facsimile: (508) 797-4014

    With a copy to:     Shulman, Rogers, Gandal, Pordy &
                        Ecker, P.A.,
                        11921 Rockville Pike, Third Floor,
                        Rockville, Maryland 20852,
                        Attention: Edward M. Hanson, Esquire
                        Telephone: (301) 230-5210
                        Facsimile: (301) 230-2891

    To Purchaser:       Alexandria Real Estate Equities, Inc.
                        251 South Lake Drive, Suite 700
                        Pasadena, California 91101
                        Attention:   Joel S. Marcus
                                     Peter Nelson
                        Telephone:   (818) 578-0777
                        Facsimile:   (818) 578-0770

    With a copy to:     Skadden, Arps, Slate, Meagher & Flom LLP
                        300 South Grand Avenue
                        Los Angeles, CA 90071 -3144
                        Attention:   Rand April
                        Telephone:   (213) 687-5060
                        Facsimile:   (213) 687-5600

    With a copy to:     Alexandria Real Estate Equities, Inc.
                        11440 West Bernardo Court, Suite 170
                        San Diego, California 92127
                        Attention:   Alan D. Gold
                        Telephone:   (619) 592-6801
                        Facsimile:   (619) 592-6814


                                          30

    SECTION l6.7. SUCCESSORS BOUND.

    The provisions of this Agreement shall extend to, bind and inure to the
benefit of the parties hereto and their respective personal representatives,
heirs, successors, and permitted assigns.

    SECTION 16.8. ASSIGNMENT OF RIGHTS.

    This Agreement may be assigned by Purchaser to any third party without
Seller's prior written consent, provided that, prior to the effective date of
any such assignment (i) Purchaser shall deliver an executed copy of the
instrument of assignment to Seller and (ii) the assignee shall execute,
acknowledge and deliver to Seller (in a form reasonably satisfactory to Seller)
an agreement whereby the assignee agrees to be bound by and to perform all of
the obligations of purchaser as set forth in this Agreement. Such an assignment
shall in no way relieve Purchaser of its duty to perform fully all of its
obligations under this Agreement, and Purchaser and its assigns shall thereafter
be jointly and severally liable for the obligations of the purchaser as
described herein. Any assignment made in violation of this Section shall be
without force or effect.

    SECTION 16.9. TIME.

    Time is of the essence in the performance of the obligations of each party
as set forth in this Agreement. In the computation of any period of time
provided for in this Agreement or by law, the day of the act or event from which
said period of time runs shall be excluded, and the last day of such period
shall be included, unless it is not a business day, in which case the period
shall be deemed to run until the end of the next day which is a business day.
For all purposes of this Agreement, a "business day" means any day other than a
Saturday, Sunday, or other day on which commercial banks are authorized or
required to close under the laws of the State of Maryland.

    SECTION 16. 10. EXHIBITS.

    All Exhibits to this Agreement are incorporated herein by reference.

    SECTION 16.11. CAPTIONS.

    The captions of the various sections and paragraphs of this Agreement have
been inserted only for the purpose of convenience; such captions are not a part
of this Agreement and shall not be deemed in any manner to modify, explain,
enlarge or restrict any of the provisions of this Agreement.



                                          31
    SECTION 16.12. INVALIDITY.

    If any term, covenant, or condition of this Agreement or the application
thereof to any person or circumstances shall be invalid or unenforceable (other
than a provision imposing limited liability upon a party), the remainder of this
Agreement, or the application of such term, covenant or condition to persons or
circumstances other than those to which it is held invalid or unenforceable,
shall not be affected thereby, and each term, covenant and condition shall be
valid and enforceable to the fullest extent permitted by law.

    SECTION 16. 13. ESCROW AGENT.

    Escrow Agent's signature hereto constitutes acknowledgment of receipt of
the Deposit only. Seller and Purchaser agree that Escrow Agent assumes no
responsibility for, and shall not be liable for, the performance of the
obligations of either Seller or Purchaser as contained in this Agreement. Escrow
Agent is only obligated to hold the Deposit in escrow and to deliver it in the
manner described herein. Escrow Agent may act upon any instrument or other
writing (and upon signatures of the parties hereto) believed by it in good faith
to be genuine, without any further duty of independent verification. In the
event of any dispute with respect to the transactions described in this
Agreement, Escrow Agent shall be entitled to deliver the Deposit to a court 
with appropriate jurisdiction without first acquiring the approval or either
Seller or Purchaser, thereby relieving itself from all further duties or
responsibilities with respect thereto.

    SECTION 16.14. POST CLOSING ACCESS TO RECORDS. Upon receipt by Seller of
Purchaser's reasonably written request at any time and from time to time within
a period of one (1) year after the Closing, Seller shall, at Seller's principal
place of business, during Seller's normal business hours, make available to
Purchaser for inspection and copying (at Purchaser's sole cost and expense) all
of Seller's books and records for the period for which Purchaser is required to
have audited financial statements prepared with respect to the Property as may
be required by the Securities and Exchange Commission and/or Purchaser's
auditors to the extent that such books and records and related information are
in Seller's possession or control. Seller agrees to provide to Purchaser's
auditor a representation letter, in substantially the form of EXHIBIT "K"
attached hereto, regarding such books and records. The provisions of this
Section 16.14 shall survive the Closing for a period of one (1) year.


                              [SIGNATURES ON NEXT PAGE]




                                      32

    IN WITNESS WHEREOF, this Agreement has been duly executed by the parties on
the day and year noted below for each, and the "Execution Date" of this
Agreement shall be the latest date on which Seller and Purchaser shall have
executed this Agreement.


                                            SELLER:
                                            AQUILA BIOPHARMACEUTICALS, INC.
WITNESS:

/s/ Stephen Di Palma                        By: /s/ ALISON TAUNTON-RIGBY
- -----------------------                        ------------------------------
                                            Name:   ALISON TAUNTON-RIGBY
                                                 ----------------------------
                                            Title: PRESIDENT & CEO
                                                  ---------------------------
DATED: 9/29/97
      -----------------
                                            PURCHASER: 
                                            ALEXANDRIA REAL ESTATE
                                            EQUITIES, INC.
WITNESS:
 
/s/ Gary A. Kreitzer                        By: /s/ ALAN D. GOLD
- -----------------------                        ------------------------------
                                            Name: ALAN D. GOLD
                                                 ----------------------------
                                            Title: PRESIDENT
                                                  ---------------------------
DATED: SEPT 29, 1997
      -----------------



                            ACKNOWLEDGMENT BY ESCROW AGENT

    The undersigned joins in the execution of this Agreement solely to serve as
the "Escrow Agent" pursuant to this Agreement and agrees to hold the Deposit in
escrow and to disburse same in accordance with the provisions of this Agreement.

                                          Chicago Title Insurance Company

                                          By: /s/ Charles S. Carroccio Jr.
                                             ----------------------------
                                          Name: Charles S. Carroccio Jr.
                                               --------------------------
                                          Title: Office Counsel
                                                -------------------------
                                          Date: October 1, 1997
                                                ----------------




                             LIST OF EXHIBITS

    Exhibit "A"    -    Legal Description of the Land

    Exhibit "B"    -    List of Personal Property being Conveyed to Purchaser

    Exhibit "C"    -    Operating Statements for the Property (full 1996;
                        partial 1997)

    Exhibit "D"    -    Rent Roll and Description of Leases

    Exhibit "E"    -    List of Service Contracts (with copies thereof)

    Exhibit "F"    -    Qualifications to Seller's Representation re: Hazardous 
                        Materials

    Exhibit "G"    -    Form of Tenant Estoppel Certificate

    Exhibit "H"    -    List of Approvals

    Exhibit "I"    -    List of Insurance Policies Maintained by Seller in 
                        connection with its Ownership of the Property

    Exhibit "J"    -    Form of Special Warranty Deed

    Exhibit "K"    -    Form of Representation Letter

    Exhibit "L"    -    Form of Certificate of Seller and Purchaser

    Exhibit "M"    -    Form of Assignment of Leases

    Exhibit "N"    -    Form of Bill of Sale




                                     EXHIBIT "A"

                                 DESCRIPTION OF LAND

Those two (2) certain properties located in Montgomery County, Maryland more 
particularly described as follows:

Lot numbered Five (5) in Block lettered "A" in the subdivision known as "RED 
GATE INDUSTRIAL PARK" as shown on a plat thereof recorded in Plat Book 102, 
Plat 11503 among the Land Records of Montgomery County, Maryland, more 
commonly known as 3 Taft Court, Rockville, Maryland 20850.

Lot numbered Nine (9) in Block lettered "B" in the subdivision known as "RED 
GATE INDUSTRIAL PARK" as shown on a plat thereof recorded in Plat Book 114 
at Plat 13548 among the Land Records of Montgomery County, Maryland, together 
with Access Easement for Lot Nine (9) across Lot Ten (10) as shown on the 
plat recorded at Plat Book 114 at Plat 13548 among the Land Records of 
Montgomery County, Maryland, more commonly known as 1500 East Gude Drive, 
Rockville, Maryland 20850.



                                     EXHIBIT "B"

             LIST OF PERSONAL PROPERTY BEING CONVEYED TO PURCHASER


                                          NONE






                                       EXHIBIT C

                                          TOTAL     1997 thru
                                           1996       8/31/97
                                       ----------   -----------
RENTAL INCOME:

    BBI @ 3 Taft Court                   268,840      193,013
    CBC @ 1500 EGD &  3 1/2 Taft          92,671      317,730
    Expense reimbursement                 42,089       73,405
                                       ----------   -----------
    Totals                               403,600      584,148

RENTAL EXPENSES:

    Mortgage payments                    112,731      366,224
    Depreciation                         136,976      103,188
    Real estate taxes                    101,437       69,772
    Insurance                             16,165       10,777
    Building maintenance                   7,195        6,827
    Building cleaning                      2,430            0
    Building security                     23,542            0
                                       ----------   -----------
    Totals                               400,476      556,788
                                       ----------   -----------
Net rental income/(loss)                   3,124       27,360
                                       ----------   -----------
                                       ----------   -----------



                                 EXHIBIT "D"

                      RENT ROLL AND DESCRIPTION OF LEASES



                                     EXHIBIT "E"

                List of Service Contracts (with copies thereof)


                                         NONE


                                    EXHIBIT F

    There is one underground tank used to store diesel fuel for emergency
generators located behind 3 Taft Court.



                                     EXHIBIT "G"

                         Form of Tenant Estoppel Certificate

                                 ESTOPPEL CERTIFICATE

            THIS TENANT ESTOPPEL CERTIFICATE ("CERTIFICATE"), dated as of 
_______________, 1997, is executed by ______ ("TENANT") in favor of 
Alexandria Real Estate Equities, Inc., a Maryland corporation, together with 
its nominees, assignees and assigns (collectively, "BUYER") and in the favor 
of _______________-_______________________, a _______________ corporation, 
together with its nominees, designees and assigns (collectively, "LENDER").

                                   RECITALS

     A. Buyer and Aquila BioPharmaceuticals, Inc., a Delaware corporation 
("LANDLORD"), have entered into that certain Purchase Agreement, dated as of 
_____________, 1997 (the "PURCHASE AGREEMENT"), whereby Buyer has agreed to 
purchase, among other things, the improved real property located in the City 
of Rockville, County of Montgomery, State of Maryland, more particularly 
described on Exhibit "A" attached to the Purchase Agreement (the "PROPERTY").

     B. Tenant and Landlord (or its predecessor-in-interest) have entered 
into that certain Lease Agreement, dated as of ________________ (together 
with all amendments, modifications, supplements, guarantees and restatements 
thereof, the "Lease"), for a portion of the Property.

    C. Pursuant to the Lease, Tenant has agreed that upon the request of
Landlord, Tenant would execute and deliver an estoppel certificate certifying
the status of the Lease.

    D. In connection with the Purchase Agreement, Landlord has requested that
Tenant execute this Certificate with an understanding that Lender will rely on
the representations and agreements below in granting to Buyer a loan.

    NOW, THEREFORE, Tenant certifies, warrants, and represents to Buyer and
Lender as follows:



                                    AGREEMENT
          SECTION 1. LEASE.

     Attached hereto as Exhibit "1" is a true, correct and complete copy of
the Lease, including the following amendments, modifications, supplements,
guarantees and restatements thereof, which together represent all of the
amendments, modifications, supplements, guarantees and restatements thereof:
____________________________________________________________________________
______________________________________________________________________.
(If none, please state "None.")

          SECTION 2. LEASED PREMISES.

     Pursuant to the Lease, Tenant leases those certain premises (the "LEASED 
PREMISES:") consisting of approximately _________________ (___________) 
rentable square feet within the Property, as more particularly described in 
the Lease. In addition, pursuant to the terms of the Lease, Tenant has the 
[non-exclusive] right to use [____________ parking spaces/the parking area] 
located on the Property during the term of the Lease. [Cross-out the preceding
sentence or portions thereof if inapplicable.]

          SECTION 3. FULL FORCE OF LEASE.

     The Lease has been duly authorized, executed and delivered by Tenant, is 
in full force and effect has not been terminated and constitutes a legally 
valid instrument, binding and enforceable against Tenant in accordance with 
its terms, subject only to applicable limitations imposed by laws relating to 
bankruptcy and creditor's rights.

          SECTION 4. COMPLETE AGREEMENT.

     The Lease constitutes the complete agreement between Landlord and Tenant 
for the Leased Premises and the Property, except as modified by the Lease 
amendments noted above (if any), has not been modified, altered or amended.

          SECTION 5. ACCEPTANCE OF LEASED PREMISES.

     Tenant has accepted possession and is currently occupying the Leased
Premises.



          SECTION 6. LEASE TERM.

     The term of the Lease commenced on _________________ and ends on 
_______________, subject to the following options to extend: ________________
__________________________________________________________________.
(If none, please state "None.")

          SECTION 7. PURCHASE RIGHTS.

     Tenant has no option, right of first refusal, right of first offer, or
other right to acquire or purchase all or any portion of the Leased Premises or
all or any portion of, or interest in, the Property, except as follows:_________
_______________________________________________________________________________.
(If none, please state "None.")

          SECTION 8. RIGHTS OF TENANT.

     Except as expressly stated in this Certificate, Tenant:

     (a) has no right to renew or extend the term of the Lease;

     (b) has no option or other right to purchase all or any part of the Leased
Premises or all or any part of the Property;

     (c) has no right, title, or interest in the Leased Premises, other than as
Tenant under the Lease.

          SECTION 9. RENT.

          (a) The obligation to pay rent under the Lease commenced on 
____________. The rent under the Lease is current, and Tenant is not in 
default in the performance of any of its obligations under the Lease.

          (b) Tenant is currently paying base rent under the Lease in the 
amount of _______________ Dollars ($_________) per month. Tenant has not 
received and is not, presently, entitled to any abatement, refunds, rebates, 
concessions or forgiveness of rent or other charges, free rent, partial rent, 
or credits, offsets or reductions in rent, except as follows:________________
_____________________________________________________.
(If none, please state "None.")



          (c) Tenant's estimated share of operating expenses, common area 
charges, insurance, real estate taxes and administrative and overhead 
expenses is ______ percent (____%) and is currently being paid at the rate 
of ___________________ Dollars ($______) per month, payable to 
_________________.

          (d) There are no existing defenses or offsets against rent due or 
to become due under the terms of the Lease, and there presently is no default 
or other wrongful act or omission by Landlord under the Lease or otherwise in 
connection with Tenant's occupancy of the Leased Premises, nor is there a 
state of facts which with the passage of time or the giving of notice or both 
could ripen into a default on the part of Tenant, or to the best knowledge of 
Tenant, could ripen into a default on the part of Landlord under the Lease, 
except as follows: _________________________________________________________
____________________________________________________________________________
(If none, please state "None.")

          SECTION 10. SECURITY DEPOSIT.

     The amount of Tenant's security deposit held by Landlord under the Lease is
______________________ Dollars ($______).

          SECTION 11. PREPAID RENT.

     The amount of prepaid rent, separate from the security deposit, is
_____________________ Dollars ($______ ), covering the period from 
_________________ to _________________________.

          SECTION 12. INSURANCE.

     All insurance, if any, required to be maintained by Tenant under the Lease
is presently in effect.

          SECTION 13. PENDING ACTIONS.

     There is not pending or, to the knowledge of Tenant, threatened against 
or contemplated by the Tenant, any petition in bankruptcy, whether voluntary 
or otherwise, any assignment for the benefit of creditors, or any petition 
seeking reorganization or arrangement under the federal bankruptcy laws or 
those of any state.



          SECTION 14. TENANT IMPROVEMENTS.

     As of the date of this Certificate, to the best of Tenant's knowledge, 
Landlord has performed all obligations required of Landlord pursuant to the 
Lease; no offsets, counterclaims, or defenses of Tenant under the Lease exist 
against Landlord; and no events have occurred that, with the passage of time 
or the giving of notice, would constitute a basis for offsets, counterclaims, 
or defenses against Landlord, except as follows:_______________________________
____________________________________________________________________________.
(If none, please state "None.")

          SECTION 15. ASSIGNMENTS BY LANDLORD.

     Tenant has received no notice of any assignment, hypothecation or pledge 
of the Lease or rentals under the Lease by Landlord. Tenant hereby consents 
to an assignment of the lease and rents to be executed by Landlord to Buyer 
or Lender in connection with the Loan and acknowledges that said assignment 
does not violate the provisions of the Lease. Tenant acknowledges that the 
interest of the Landlord under the Lease is to be assigned to Buyer or Lender 
solely is security for the purposes specified in said assignment and Buyer or 
Lender shall have no duty, liability or obligation whatsoever under the Lease 
or any extension or renewal thereof, either by virtue of said assignment or 
by any subsequent receipt or collection of rents thereunder, unless Buyer or 
Lender shall specifically undertake such liability in writing. Tenant agrees 
that upon receipt of a written notice from Buyer or Lender of a default by 
Landlord under the Loan, Tenant will thereafter pay rent to Buyer or Lender 
in accordance with the terms of the Lease.

          SECTION 16. ASSIGNMENTS BY TENANT.

     Tenant has not sublet or assigned the Leased Premises or the Lease or 
any portion thereof to any sublessee or assignee. No one except Tenant and 
its employees will occupy the Leased Premises. The address for notices to be 
sent to Tenant is as set forth in the Lease.

          SECTION 17. ENVIRONMENTAL MATTERS.

     The operation and use of the Leased Premises does not involve the 
generation, treatment, storage, disposal or release into the environment of 
any hazardous materials, regulated materials and/or solid waste, except those 
used in the ordinary course of operating Tenant's business and in all events 
are generated, used stored and disposed of in accordance with all applicable 
laws.



          SECTION 18. SUCCESSION OF INTEREST.

     Tenant agrees that, in the event Buyer or Lender succeeds to interest of
Landlord under the Lease:

          (a) Buyer or Lender shall not be liable for any act or omission of 
any prior landlord (including Landlord);

          (b) Buyer or Lender shall not be liable for the return of any 
security deposit;

          (c) Buyer or Lender shall not be bound by any rent or additional 
rent which Tenant might have prepaid under the Lease for more than the 
current month;

          (d) Buyer or Lender shall not be bound by any amendments or 
modifications of the Lease made without prior consent of Buyer or Lender;

          (e) Buyer or Lender shall not be subject to any offsets or defenses 
which Tenant might have against any prior landlord (including Landlord); or

          (f) Buyer or Lender shall not be liable under the Lease to Tenant 
for the performance of Landlord's obligations under the Lease beyond Buyer or 
Lender's interest in the Property.

         SECTION 19. NOTICE OF DEFAULT.

     Tenant agrees to give Buyer and Lender a copy of any notice of default 
under the Lease served upon Landlord at the same time as such notice is given 
to the Landlord. Tenant further agrees that if Landlord shall fail to cure 
such default within the applicable grace period, if any, provided in the 
Lease, then Buyer or Lender shall have an additional sixty (60) days within 
which to cure such default, or if such default cannot be cured within such 
sixty (60) day period, such sixty (60) day period shall be extended so long 
as Buyer or Lender has commenced and is diligently pursuing the remedies 
necessary to cure such default (including, but not limited to, commencement 
of foreclosure proceedings, if necessary to effect (such cure), in which 
event the Lease shall not be terminated while such remedies are being pursued.

          SECTION 20. NOTIFICATION BY TENANT.

     From the date of this Certificate and continuing until ___________, 
Tenant agrees to immediately notify Buyer and Lender, in writing by 
registered or certified mail, return receipt requested, at the following 
addresses, on the occurrence of any event or the



discovery of any fact that would make any representation contained in this 
Certificate inaccurate:

If To Buyer:     Alexandria Real Estate Equities, Inc.
                 251 South Lake Avenue, Suite 535
                 Pasadena, California 91101
                 Attention: Joel S. Marcus

With A Copy To:  Skadden, Arps, Slate, Meagher & Flom LLP
                 300 South Grand Avenue, Suite 3400
                 Los Angeles, California 90071
                 Attention: Rand S. April

If To Lender:    
                 -----------------------------------------

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

                 -----------------------------------------
                 Attention:
                            ------------------------------

     Tenant makes this Certificate with the knowledge that it will be relied 
upon by Buyer and Lender in agreeing to purchase the Property.

     Tenant has executed this Certificate as of the date first written above 
by the person named below, who is duly authorized to do so.

                                     TENANT

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

                                     By:
                                        ----------------------------------
                                     Name:
                                     Its:



                                       EXHIBIT H

None


                                      EXHIBIT I

Package Policy, including:

    Property & Casualty
    General Liability
    Rent Loss

Boiler & Machinery

Umbrella Liability

Excess Umbrella Liability


                                      EXHIBIT J"

                            FORM OF SPECIAL WARRANTY DEED

                                SPECIAL WARRANTY DEED

                                                     -------------------------
                                                     Tax Account No./Parcel ID

     Made this __ day of ________________ , 1997, by and between
AQUILA BIOPHARMACEUTICALS, INC., a Delaware corporation, party of the
first part, and ALEXANDRIA REAL ESTATE EQUITIES, INC., a Maryland corporation,
party of the second part:

     Witnesseth, that in consideration of SIX MILLION FIVE HUNDRED THOUSAND 
DOLLARS ($6,500,000.00), the receipt of which is hereby acknowledged, and 
which the party of the first part certifies under the penalty of perjury as 
the actual consideration paid, the said party of the first part does hereby 
grant, convey, bargain and sell unto the party of the second part, its 
successors and assigns in fee simple absolute all that improved property 
situate, lying and being in Montgomery County, State of Maryland and more 
particularly described on EXHIBIT "A", attached hereto and made a part hereof 
for all purposes (the "PROPERTY");

     SUBJECT to covenants, easements, rights of way and restrictions of record.

     TO HAVE AND TO HOLD the Property hereby intended to be conveyed, 
together with the buildings and improvements thereupon erected, made or 
being, and all and every title, rights, privileges, appurtenances and 
advantages "thereunto belonging, or in any wise appertaining, unto and for the 
proper use only, benefit and behoof forever of said party of the second part, 
its successors and assigns, in fee simple absolute.

    AND the said party of the first part covenants that it will warrant 
specially the property hereby conveyed, and that it will execute such further 
assurances of the Property as may be requisite or necessary.



    IN TESTIMONY WHEREOF, the said party of the first part has set its hand and
seal the year and day first above written.

                                  AQUILA BIOPHARMACEUTICALS, INC.,
                                  a Delaware corporation

                                                                     (SEAL)
- ----------------------------       ----------------------------------
                                   By:

                                                                     (SEAL)
- ----------------------------       ----------------------------------
                                   By:

STATE OF _______________ )
COUNTY OF _______________) SS.

         I HEREBY CERTIFY that on this ___ day of _____________, 1997, before 
me, the undersigned officer, a Notary Public in and for the State and County 
aforesaid, personally appeared __________________, who acknowledged himself 
to be the ______________________ of AQUILA BIOPHARMACEUTICALS, INC., and that 
he, as such officer, being duly authorized so to do, executed the foregoing 
instrument for the purposes therein contained by signing the name of said 
corporation by himself as such officer.

                                   WITNESS MY HAND AND NOTARIAL SEAL.

                                   ---------------------------------- 
                                                             , Notary


                                     EXHIBIT "K"

                            FORM OF REPRESENTATION LETTER


                                      EXHIBIT K
Date

Ernst & Young LLP
2049 Century Park East
Suite 1700
Los Angeles, CA 90067

Re: The statement of revenue and certain expense of "NAME OF PROPERTY"

In connection with your audits of the statement of revenue and certain expenses
of "NAME OF PROPERTY" for the period, we recognize that obtaining
representations from us concerning the information contained in this letter is a
significant procedure in enabling you to form an opinion whether the statement
of revenue and certain expenses presently fairly, in all material respects, the
results of operations of "NAME OF PROPERTY" in conformity with generally
accepted accounting principles and accordingly, we make the following
representations, which are true to the best of our knowledge and belief.

GENERAL

We recognize that, as members of management of "NAME OF PROPERTY" we are
responsible for the fair presentation of its statement of revenue and certain
expenses. We believe the statement of revenue and certain expenses is fairly
presented in conformity with generally accepted accounting principles applied on
a consistent basis.

We have provided to your representatives all financial records and related data.

We had no plans or intentions that would have materially affect all carrying
value or classification of the property's assets and liabilities.

INTERNAL CONTROL

There are no material transactions that have not been properly recorded in the
accounting records underlying the statement of revenue and certain expenses.
There are no material weaknesses in internal control, including any for which we
believe the cost of corrective actions exceeds the benefits. There have been no
significant changes in internal controls since the date of acquisition.



                                                                          Page 2
Ernst & Young LLP                                         ________________, 1997

RISKS AND UNCERTAINTIES

To the best of our knowledge there are no risks and uncertainties related to 
certain significant estimates and current vulnerabilities due to certain 
concentrations that have not been disclosed.

RECEIVABLES

Adequate provision has been made for material losses, costs and expenses that 
may be incurred subsequent to the date of acquisition for uncollectible 
accounts and discounts, etc., that may be incurred in the collection of 
receivables at that date.

CONTINGENT LIABILITIES

There are no unasserted claims or assessments, including those our lawyers 
have advised us of, that are probable of assertion and must be disclosed.

There have been no violations or possible violations of laws or regulations 
in any jurisdiction whose effects should be considered for disclosure in the 
statement of revenue and certain expenses or as a basis for recording a loss 
contingency.

There are no other material liabilities or gain or loss contingencies that 
are required to be accrued or disclosed. 

IRREGULARITIES

There have been no irregularities involving management or employees who have
significant roles in internal control. There have been no irregularities
involving other employees that could have a material effect on the statement of
revenue and certain expenses.

There are no instances where any officer of employee of "NAME OF PROPERTY" has
an interest in a company that which "NAME OF PROPERTY" does business that
would be considered a "conflict of interest."  Such an interest would be
contrary to "NAME OF PROPERTY" policy.

SUBSEQUENT EVENT

No event or transactions have occurred since the date of acquisition or are
pending that would have a material effect on the financial statement at that
date or for the period then ended, or that are of such signifcance in relation
to "NAME OF PROPERTY" affairs to require mention in a note to the statement of
revenue and certain expenses in order to make them not misleading regarding 
the results of operations of "NAME OF PROPERTY".


                                                                          Page 3
Ernst & Young LLP                                         ________________, 1997

We understand that your audits were conducted in accordance with generally
accepted auditing standards as defined and described by the American Institute
of Certified Public Accountants  and were, therefore, designed primarily for the
purpose of expressing an opinion on the statement of revenue and certain
expenses of "NAME OF PROPERTY" taken as a whole, and that your tests of the 
accounting records and other auditing procedures were limited to those that you
considered neccessary for that purpose.

Very truly yours,

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

    By:
       ---------------------------
       By:
          ------------------------

              By:
                 -----------------

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

    By:
       ---------------------------
       By:
          ------------------------

              By:
                 -----------------

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

    By:
       ---------------------------
       By:
          ------------------------

              By:
                 -----------------


                                     EXHIBIT "L"

                     FORM OF CERTIFICATE OF SELLER AND PURCHASER

                          SELLER'S [PURCHASER'S] CERTIFICATE

     The undersigned hereby certifies to ALEXANDRIA REAL ESTATE EQUITIES, 
INC. ("Buyer") [AQUILA BIOPHARMACEUTICALS, INC. ("Seller")] that, as of the 
date hereof,

     (i) all of the representations, covenants and warranties of AQUILA 
BIOPHARMACEUTICALS, INC. ("Seller") [ALEXANDRIA REAL ESTATE EQUITIES, INC. 
("Buyer")] made in or pursuant to that certain Purchase Agreement, dated as 
of ________________, 1997, between Seller and Buyer (the "Agreement") are 
true, accurate, correct and complete in all material respects, except as 
otherwise expressly disclosed in the schedule of exceptions attached to this 
Certificate;

     (ii) all conditions to the Closing (as such term is defined in the
Agreement) that Seller [Buyer] was to satisfy or perform have been satisfied and
performed in all material respects, except as otherwise expressly disclosed in
the schedule of exceptions attached to this Certificate; and

     (iii) all conditions to the Closing that Buyer [Seller] was to satisfy or
perform to obligate Seller [Buyer] to consummate the Closing have been satisfied
and performed in all material respects, except as otherwise expressly disclosed
in the schedule of exceptions attached to this Certificate.


Dated:                               AQUILA BIOPHARMACEUTICALS, INC.
      ---------------                [ALEXANDRIA REAL ESTATE EQUITIES, INC.]

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


                                     EXHIBIT "M"

                             FORM OF ASSIGNMENT OF LEASES

                      ASSIGNMENT OF LEASES AND SECURITY DEPOSITS

     THIS ASSIGNMENT OF LEASES AND SECURITY DEPOSITS ("ASSIGNMENT") is entered 
into as of the __day of _____________, 1997, by and between AQUILA 
BIOPHARMACEUTICALS, INC., a Delaware corporation ("ASSIGNOR"), and ALEXANDRIA 
REAL ESTATE EQUITIES, INC., a Maryland corporation ("ASSIGNEE").

                                   R E C I T A L S

     WHEREAS, Assignor (or its predecessor-in-interest), as landlord, has
entered into those certain leases identified on Exhibit " __" attached hereto
and incorporated herein by reference (collectively, together with all
amendments, modifications, supplements, restatements and guarantees thereof,
the "LEASES"), for certain property located in the City of Rockville, County of
Montgomery, State of Maryland;

     WHEREAS, Assignor and Assignee have entered into that certain Purchase
Agreement, dated as of             , 1997 (the "PURCHASE AGREEMENT"); and

     WHEREAS, the Purchase Agreement requires Assignor and Assignee to execute
this Assignment;

     NOW, THEREFORE, for good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, Assignor and Assignee hereby agree
as follows:

                                    AGREEMENT

    1. ASSIGNMENT AND ASSUMPTION. Assignor hereby irrevocably assigns, sets
over, transfers and conveys to Assignee all of Assignor's right, title and
interest in and to (i) the Leases and (ii) all security deposits made under the
Leases (the "SECURITY DEPOSITS"), which assignment shall be effective from and
after the date hereof for the remainder of the term of each of the Leases.
Subject to the terms and conditions of the Purchase Agreement, Assignee hereby
accepts this Assignment of the Leases and Security Deposits and the rights
granted herein. Assignee hereby expressly assumes, for itself and its
successors, assigns and legal representatives, the Leases and all of the
obligations and liabilities, fixed and contingent, of Assignor thereunder
accruing from and after the date hereof with respect to the Leases and agrees to
(a) be fully bound by all of the terms, covenants, agreements, provisions,
conditions, obligations and liability of Assignor thereunder, which accrue from
the date hereof, and (b) keep, perform and observe all of



the covenants and conditions contained therein on the part of Assignor to be
kept, performed and observed, from and after the date hereof.

     2. INDEMNIFICATIONS. Assignor hereby agrees to indemnify, protect, 
defend and hold Assignee harmless from and against any and all claims, 
losses, damages, costs and expenses (including, without limitation, 
reasonable attorney's fees and disbursements) incurred or suffered by 
Assignee in connection with the Leases and arising prior to the Closing (as 
defined in the Purchase Agreement). Assignee hereby agrees to indemnify, 
protect, defend and hold Assignor harmless from and against any and all 
claims, losses, damages, costs and expenses (including, without limitation, 
reasonable attorney's fees and disbursements) incurred or suffered by 
Assignor in connection with the Leases and arising on or after the Closing.

     3. GENERAL PROVISIONS.

          a. SUCCESSORS. This Assignment shall be binding upon and inure to the
benefit of the parties hereto and their respective heirs, legal representatives,
successors and assigns.

          b. COUNTERPARTS. This Assignment may be executed in as many 
counterparts as may be deemed necessary and convenient, and by the different 
parties hereto on separate counterparts, each of which when so executed, 
shall be deemed an original, but all such counterparts shall constitute one 
and the same instrument.

          c. GOVERNING LAW. This Assignment and the legal relations of the 
parties hereto shall be governed by and construed and enforced in accordance 
with the laws of the State of Maryland, without regard to its principles of 
conflicts of law.



     IN WITNESS WHEREOF, this Assignment was made and executed as of the date
first above written.

                                       ASSIGNOR

                                       AQUILA BIOPHARMACEUTICALS, INC.
                                       a Delaware corporation

                                       By:
                                          ----------------------------
                                       Name:
                                       Its:

                                       ASSIGNEE

                                       ALEXANDRIA REAL ESTATE EQUITIES,
                                       INC., a Maryland corporation

                                       By:
                                          ----------------------------
                                       Name:
                                       Its:



                                     EXHIBIT " "
                       (to Exhibit "M" -- Assignment of Leases)

                                    LIST OF LEASES

    1.   [Name of Lease], dated as of ______, by and between
         ____________________ and ______________.

    2.   [Name of Lease], dated as of ______ , by and between
         ____________________ and ______________.

    3.   [Name of Lease], dated as of ______ , by and between
         ____________________ and ______________.



                                     EXHIBIT "N"

                                 FORM OF BILL OF SALE

                                     BILL OF SALE

    THIS BILL OF SALE ("BILL OF SALE") is made as of the ____ day of 
______________, 1997, by AQUILA BIOPHARMACEUTICALS, INC., a Delaware 
corporation ("SELLER"), to ALEXANDRIA REAL ESTATE EQUITIES, 
[INC., a Maryland partnership ("BUYER").

                                R E C I T A L S

     WHEREAS, Seller is the owner of that certain real property located in 
the City of Rockville, County of Montgomery, State of Maryland (the "REAL 
PROPERTY"), as more particularly described on Exhibit "A" attached hereto and 
incorporated herein by reference;

     WHEREAS, Buyer and Seller have entered into that certain Purchase 
Agreement (the "PURCHASE AGREEMENT"), dated as of _______________, 1997, with 
respect to, among other things, the acquisition of the "Personal Property" 
and the "Intangible Property" (each as defined below), and certain other 
property; and

     WHEREAS, the Purchase Agreement requires Seller to convey all of 
Seller's right, title and interest in, to and under the Personal Property and 
the Intangible Property to Buyer;

     NOW, THEREFORE, for good and valuable consideration, the receipt and 
sufficiency of which are hereby acknowledged, Seller hereby agrees as follows:

                                  A G R E E M E N T

    1. Unless the context otherwise requires, all capitalized terms used but 
not otherwise defined herein shall have the respective meanings provided 
therefor in the Purchase Agreement.

    2. Seller does hereby unconditionally, absolutely, and irrevocably grant, 
bargain, sell, transfer, assign, convey, set over and deliver unto Buyer all 
of Seller's right, title and interest in and to:

         a. all of that certain tangible personal property now owned by 
Seller and located on the Land or Improvements or attached thereto, and used 
in connection with the use, operation, maintenance or repair thereof, 
(collectively, the "PERSONAL PROPERTY"), all as more particularly described 
on Exhibit "B" attached hereto and incorporated herein by reference; and



          b. all of that certain intangible property now or hereafter owned 
by Seller and used in connection with the Land, the Improvements or the 
Personal Property, including, without limitation, the Leases and the Service 
Contracts, building names, architectural, site, landscaping or other permits, 
applications, authorizations and other entitlement, transferable guarantees 
and warranties covering the Land and/or Improvements, together with all 
transferable contract rights, books, records, reports, test results, 
environmental assessments, as-built plans, specifications and other similar 
documents and materials relating to the use or operation, maintenance or 
repair of the Property or the construction or fabrication thereof, and all 
transferable utility contracts (collectively, the "INTANGIBLE PROPERTY" and, 
together with the Personal Property, the "PROPERTY").

     3. Buyer hereby expressly assumes, for itself and its successors, 
assigns and legal representatives, the Leases and the Service Contracts and 
all of the obligations and liabilities, fixed and contingent, of Seller 
thereunder accruing from and after the date hereof with respect thereto and 
agrees to (a) be fully bound by all of the terms, covenants, agreements, 
provisions, conditions, obligations and liability of Seller thereunder, which 
accrue from the date hereof, and (b) keep, perform and observe all of the 
covenants and conditions contained therein on the part of Seller to be kept, 
performed and observed, from and after the date hereof.

     4. Seller represents and warrants that the Property is free and clear of 
all options, liens, mortgages, pledges, security interests, covenants, prior 
assignments, encumbrances and claims of any nature, other than the Permitted 
Exceptions.

     5. Seller hereby agrees to indemnify, protect, defend and hold Buyer 
harmless from and against any and all claims, losses, damages, costs and 
expenses (including, without limitation, reasonable attorney's fees and 
disbursements) incurred or suffered by Buyer in connection with the Property 
and arising prior to the Closing. Buyer hereby agrees to indemnify, protect, 
defend and hold Seller harmless from and against any and all claims, losses,
damages, costs and expenses (including, without limitation, reasonable 
attorney's fees and disbursements) incurred or suffered by Seller in 
connection with the Property and arising on or after the Closing.

     6. This Bill of Sale shall be binding upon and inure to the benefit of 
the parties hereto and their respective heirs, legal representatives, 
successors and assigns.

     7. This Bill of Sale and the legal relations of the parties hereto shall 
be governed by and construed and enforced in accordance with the laws of the 
State of Maryland, without regard to its principles of conflicts of law.



    IN WITNESS WHEREOF, this Bill of Sale was made and executed as of the date
first above written.

                                   SELLER:

                                   AQUILA BIOPHARMACEUTICALS, INC.,
                                   a Delaware corporation

                                   By:
                                      ----------------------------
                                      Name:
                                      Its:

                                   BUYER:

                                   ALEXANDRIA REAL ESTATE EQUITIES, INC.,
                                   a Maryland corporation

                                   By:
                                      ----------------------------
                                      Name:
                                      Its: