PEPTIDES TRAPPED ON A THREAD - C&EN Global Enterprise (ACS

Publication Date: January 30, 2006. Copyright © 2006 American Chemical Society. ACS Chem. Eng. News Archives. Cite this:Chem. Eng. News 2006, 84, 5, ...
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NEWS OF THE WEEK I N D U S T R I A L

GASES

LINDE BIDS FOR BOC BOC rejects the offer, but stock analysts are intrigued

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group BOC has rebuffed an unsolicited $13.4 billion takeover offer by German rival Linde. But the deal, which would create the world's largest producer of industrial gases, is not necessarily dead. Linde's $27 80-per-share offer represents about a 30% premium over BOC's recent share price, a handsome valuation, analysts say. But BOC, citing "preconditions" to the offer—including financing, antitrust approvals, and due diligence—has rejected it. "The board of BOC has met together with its advisers and unanimously rejected the proposal because of its preconditions and its failure to

Reitzle

value fully the growth prospects of BOC," t~e company said. Linde counters by calling the offer a "friendly approach" that would unlock synergies between the two companies and wouldn't draw the ire of antitrust regulators. The company also says financing arrangements for the cash bid are "well advanced." A stock analyst who covers BOC is puzzled at the firm's response to the bid, in which it didn't even offer to talk to Linde. "There is something in the preconditions that suggests the offer isn't straightforward," says the analyst, who asked not to be named. Although the deal might still be salvaged,

he says, to afford it, Linde would have to divest operations such as its forklift truck business, BOC's logistics business, and BOC's electronic materials business. Linde is led by Chief Executive Officer Wolfgang Reitzle; Tony Isaac is CEO of BOC. BOC was once the target of a takeover bid that it initially shunned. In 1999, Air Products & Chemicals and Air Liquide attempted to buy the company and divide its assets between them, but the U.S. Federal Trade Commission nixed the deal. In light of this failed attempt, BOC and Linde have often been mentioned in the same breath. The "BOC/Linde tie-up is the only major piece of industrial gas consolidation that could occur, given that all other combinations face too many competition overlaps," Robin Coombs, an analyst with Merrill Lynch, says in a report.—ALEX TULLO

Isaac S U P R A M O L E C U L A R

C H E M I S T R Y

PEPTIDES TRAPPED ON A THREAD Synthetic peptide rotaxanes may provide insights into natural interlocked systems

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OTAXANES DERIVED FROM

synthetic peptide macrocycles and nonpeptidic diammonium threads have been prepared by chemists at the University of Edinburgh, Scotland (J. Am. Chem. Soc., published onlineJan. 19, dx.doi.org/10.1021/ja057206q). A rotaxane is a bead-on-a-string type structure in which a linear molecule threads through at least one cyclic molecule. Bulky components at each end of the linear molecule stop the assembly from unraveling. "We've prepared the first rotaxanes that utilize cyclic peptides as the macrocyclic component," says professor of organic chemistry

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David A. Leigh, who led the synthesis team. "The work is significant," he adds, "because rotaxane architectures have been discovered in natural peptides in recent years." One notable example is the antibacterial 21-amino-acid peptide microcin J25 (C&EN, Nov. 10, 2003, page 46). "Such mechanically interlocked peptides display a wealth of intriguing properties such as high resistance to peptidases, unique modes of antimicrobial and antiviral action, impressive membrane transport characteristics, and stability to thermal and chemical denaturing," Leigh says.

His group synthesized the rotaxanes from a class ofwell-known synthetic cyclic peptides consisting of four or five repeating L-prolylglycyl units. The threads, with bulky stoppers at each end, were prepared from cationic diols containing ethane-l,2-diammonium or butane-l,4-diammonium moieties that act as templates for the cyclic components. The rotaxanes assemble by hydrogen bonding between the amide groups of the peptides and the diammonium thread units. "The hydrogen bonding is able to disrupt the intramolecular amide-amide hydrogen bonding in the cyclopeptides to such an extent that threading to form a rotaxane architecture becomes thermodynamically favorable," Leigh explains. The researchers are now trying to extend their methodology to make rotaxanes in which both the cyclic and thread components consist of peptides. "Ultimately, we would like to have generic methods for interlocking peptides," Leigh says.—MICHAEL FREEMANTLE

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