


	Stated Fixed Interest Rate		Effective Interest Rate		Principal Balance
	Stated Fixed Interest Rate		Effective Interest Rate		June 30, 2011			December 31, 2010			Maturity Date
Mortgage Notes Payable
Ardentech Court (1)	7.25	%	5.06	%	$	—		$	4,237		July 1, 2012
Center for Life Science \| Boston	7.75	%	7.75	%	343,896			345,577			June 30, 2014
500 Kendall Street (Kendall D)	6.38	%	5.45	%	63,261			64,230			December 1, 2018
6828 Nancy Ridge Drive	7.15	%	5.38	%	6,430			6,488			September 1, 2012
Road to the Cure (1)	6.70	%	5.78	%	—			14,696			January 31, 2014
10255 Science Center Drive (1)	7.65	%	5.04	%	—			10,800			July 1, 2011
Shady Grove Road	5.97	%	5.97	%	147,000			147,000			September 1, 2016
Sidney Street	7.23	%	5.11	%	26,907			27,395			June 1, 2012
Sorrento West LLC	7.42	%	2.72	%	13,112			13,247			November 10, 2011
9865 Towne Centre Drive (2)	7.95	%	7.95	%	17,528			17,636			June 30, 2013
900 Uniqema Boulevard	8.61	%	5.61	%	915			1,011			May 1, 2015
					619,049			652,317
Unamortized premiums					4,072			5,605
Mortgage notes payable, net					623,121			657,922
Notes due 2026	4.50	%	6.45	%	19,800			19,800			October 1, 2026
Unamortized discount (3)					(94		)	(278		)
Notes due 2026, net (4)					19,706			19,522
Notes due 2030	3.75	%	3.75	%	180,000			180,000			January 15, 2030
Exchangeable senior notes, net					199,706			199,522
Notes due 2016	3.85	%	3.99	%	400,000			—			April 15, 2016
Unamortized discount (5)					(2,424		)	—
Notes due 2016, net					397,576			—
Notes due 2020	6.13	%	6.27	%	250,000			250,000			April 15, 2020
Unamortized discount (6)					(2,330		)	(2,429		)
Notes due 2020, net					247,670			247,571
Unsecured senior notes, net					645,246			247,571
Unsecured line of credit (7)	1.29	%	1.29	%	121,200			392,450			July 13, 2015
Total consolidated debt					$	1,589,273		$	1,497,465

____________

(1)

During the six months ended June 30, 2011, the Operating Partnership voluntarily prepaid in full the outstanding mortgage notes totaling approximately $30.1 million pertaining to the Ardentech Court, Road to the Cure, and 10255 Science Center Drive properties, prior to their respective maturity dates.

(2)	In July 2011, the Operating Partnership voluntarily prepaid in full the outstanding mortgage note pertaining to the 9865 Towne Centre Drive property, in the amount of approximately $17.9 million including a prepayment premium of $351,000, prior to its maturity date.

(3)	The unamortized debt discount will be amortized through October 1, 2011, the first date at which the holders of the Notes due 2026 may require the Operating Partnership to repurchase the Notes due 2026.

(4)	As of June 30, 2011 and December 31, 2010, the carrying value of the equity component recognized was approximately $14.0 million.

(5)	The unamortized debt discount will be amortized through April 15, 2016, the maturity date of the Notes due 2016.

(6)	The unamortized debt discount will be amortized through April 15, 2020, the maturity date of the Notes due 2020.

(7)

At June 30, 2011, the Operating Partnership had additional borrowing capacity under the unsecured line of credit of up to approximately $591.0 million (net of outstanding letters of credit issued by the Operating Partnership and drawable on the unsecured line of credit of approximately $7.8 million). On July 14, 2011, the Operating Partnership entered into a new $750.0 million unsecured line of credit, replacing its existing line of credit, as described below in this Note 5.

On March 30, 2011, the Operating Partnership issued $400.0 million aggregate principal amount of its Notes due 2016. The purchase price paid by the underwriters was 99.365% of the principal amount and the Notes due 2016 have been recorded on the consolidated balance sheet net of the discount. The Notes due 2016 are senior unsecured obligations of the Operating Partnership and rank equally in right of payment with all other senior unsecured indebtedness of the Operating Partnership. However, the Notes due 2016 are effectively subordinated to the Operating Partnership's existing and future mortgages and other secured indebtedness (to the extent of the value of the collateral securing such indebtedness) and to all existing and future preferred equity and liabilities, whether secured or unsecured, of the Operating Partnership's subsidiaries, including guarantees provided by the Operating Partnership's subsidiaries under the Operating Partnership's unsecured line of credit. Interest at a rate of 3.85% per year is payable on April 15 and October 15 of each year, beginning on October 15, 2011, until the stated maturity date of April 15, 2016. The terms of the Notes due 2016 are governed by a base indenture and supplemental indenture, each dated March 30, 2011, among the Operating Partnership, as issuer, the Parent Company, as guarantor, and U.S. Bank National Association, as trustee.

As of June 30, 2011 and including the replacement of the existing line of credit with the new unsecured line of credit on July 14, 2011, principal payments due for the Operating Partnership's consolidated indebtedness (excluding debt premiums and discounts) were as follows (in thousands):




2011 (1)	$	17,103
2012	40,768
2013	25,370
2014	339,020
2015 (1)	127,453
Thereafter(2)	1,040,335
	$	1,590,049

____________


(1)	On July 14, 2011, the Operating Partnership entered into a new $750.0 million unsecured line of credit which matures on July 13, 2015, replacing its existing line of credit which was scheduled to mature on August 1, 2011, as described below in this Note 5.


(2)	Includes $19.8 million in principal payments of the Notes due 2026 based on a contractual maturity date of October 1, 2026 and $180.0 million in principal payments of the Notes due 2030 based on a contractual maturity date of January 15, 2030.

Subsequent Events - New Unsecured Line of Credit

On July 14, 2011, the Operating Partnership entered into an unsecured credit agreement with KeyBank National Association, as administrative agent, and certain other lenders.

The unsecured credit agreement provides for available borrowings under a revolving line of credit of $750.0 million and a maturity date of July 13, 2015, replacing the Operating Partnership's existing line of credit which was scheduled to mature on August 1, 2011. Subject to the administrative agent's reasonable discretion, the Operating Partnership may increase the amount of the revolving credit commitments to $1.25 billion upon satisfying certain conditions. In addition, the Operating Partnership, at its sole discretion, may extend the maturity date of the revolving line of credit to July 13, 2016 after satisfying certain conditions and paying an extension fee. The revolving line of credit bears interest at a floating rate equal to, at the Operating Partnership's option, either (1) reserve adjusted LIBOR plus a spread which ranges from 100 to 205 basis points, depending on the Company's credit ratings, or (2) the highest of (a) the prime rate then in effect plus a spread which ranges from 0 to 125 basis points, (b) the federal funds rate then in effect plus a spread which ranges from 50 to 175 basis points or (c) one month LIBOR plus a spread which ranges from 100 to 205 basis points, in each case, depending on the Company's credit ratings. In addition, a facility fee is payable on line capacity at an annual rate depending on the Company's credit rating, which is currently at 35 basis points.

The unsecured credit agreement includes certain restrictions and covenants which require compliance with financial covenants relating to the minimum amounts of net worth, fixed charge coverage, unsecured debt service coverage, overall leverage and unsecured leverage ratios, the maximum amount of secured indebtedness and certain investment limitations. The unsecured credit agreement specifies a number of events of default (some of which are subject to applicable cure periods), including, among others, the failure to make payments when due, noncompliance with covenants and defaults under other agreements or instruments of indebtedness. Upon the occurrence of an event of default, the lenders may terminate the revolving line of credit and declare all amounts outstanding to be immediately due and payable.