NEWS OF THE WEEK BIOMIMETICS
TOWARD A MIMIC OF PHOTOSYNTHESIS Synthetic assembly harvests light in one form and transports ions in another
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NEW ARTIFICIAL LIGHT-HAR-
vesting system has taken scientists one step closer to capturing photons and convert ing them into chemical energy as efficiently as nature does in pho tosynthesis. The self-assembling supramolecular system can also rearrange into an ion channel upon the addition of an intercalating molecule {Science 2006,313, 84). The helical photosystem's ar chitecture features π stacks of fluorescent naphthalene diimides. These novel electron-deficient chromophores are held together by a scaffold of four rigid/>-octiphenyl units. Designed and synthesized by an international team from Switzerland's University of Ge neva and Germany's University of Wurzburg, the assembly can span lipid bilayer membranes. To study the assembly's photosynthetic properties, the research ers embedded the photosystem in the wall of a vesicle containing the electron acceptor quinone. Outside the vesicle sphere, they added a sacrificial electron do nor. Irradiation with visible light produces electrons that quickly move from the donor, through the photosystem, and into the vesicle, where they reduce the quinone to hydroquinone. This photochemical process consumes all the protons within the vesicle. To refill it, the research ers add an electron-rich dialkoxynaphthalene derivative to the system. This molecule intercalates into the naphthalene diimide layers and irreversibly untwists the as sembly so that it forms a channel. The rearrangement shuts down the electron transport and allows pro tons to rush into the vesicle. "By integrating a self-assembling WWW.CEN-0NLINE.ORG
molecular gate into a vesicular membrane, they demonstrate an elegant proton-consuming and -re filling system," write University of Tokyo chemists Takuzo Aida and Kazushi Kinbara in a commentary that accompanies the paper. "Our approach is attractive be cause it identifies photosynthetic activity as a supramolecular func tion that depends directly on the precision of refined nanoarchitecture," explains Stefan Matile, the University of Geneva chemistry professor who spearheaded the re search. "In this case, quantitative, ultrafast, and long-lived charge separation can occur in response to light without any donor or ac ceptor modules attached, and the absorbed photonic energy can be converted into chemical energy." Matile admits that photosyn
EUROPEAN
thesis in lipid bilayers is primarily an academic pur suit, but he points out that the novel chromophores and new archi tecture developed for this system could have more practical applica tions. "Currently, one of our objec tives is to adapt our approach to the construction U N T W I S T I N G A molecular of multicolored dynamics simulation shows nanoarchitecture the twisted photosystem (left) on gold in the composed of π stacks of substituted hope to end up naphthalene diimides (blue) held with photovoltaic together by a scaffold of four devices," he says. rigid p-octiphenyl units (gold). < Thisfindingis Electron-rich dialkoxynaphthalene important," Matile derivatives (red) can intercalate into adds, "because it the assembly, transforming it into supports recent re an ion channel (right). ports that suggest major efforts in basic research on optoelectric nanomaterials accom plished today may have the potential to help us meet tomorrow's energy demand in a sustainable way."— BETHANY HALFORD
BUSINESS
Bayer Will Sell Diagnostics Line To Siemens
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ess than two weeks after gaining control of drugmaker Schering AG, Bayer has an nounced plans to sell its own diagnostics business to Siemens for just under $5.4 billion. "This decision is fully in line with our strategy for systematically aligning our health care busi ness," says Bayer board Chairman Werner Wenning. "We are concentrating on pharmaceuticals for both humans and animals and products that can be promoted directly to patients." The business being sold has an emphasis on hardware, information technology networking, and equipment service, Wenning explains. This emphasis makes the business subject to suc cess factors that are different from other Bayer HealthCare divisions, he says. The consumer-influenced diabetes care di vision is not affected by the transaction, Wen ning adds, nor is Schering's diagnostic imag ing business, which concentrates on contrast agents. That diagnostics business will become
part of Bayer Schering Pharma, being formed by combining newly acquired Schering with Bayer HealthCare. For Siemens, the acquisition provides an op portunity to help build what Erich R. Reinhardt, chief executive officer of Siemens Medical Solu tions, envisages as "the industry's first integrat ed diagnostics company that combines diagnostic imaging, laboratory diagnostics, and clinical in formation technology under one roof right along the value chain." Bayer's diagnostics business had about $1.8 billion in sales last year, up 8.4% from 2004. It employs more than 5,000 people worldwide. Although Bayer insists that the diagnostics deal was being pursued independently of the Schering acquisition, the company notes that the proceeds from the sale will help pay for Scher ing. "The effect of this divestment is to substan tially reduce our debt, thus helping to improve our credit profile," Wenning says.—PATRICIA SHORT
C&EN / J U L Y
10, 2006
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