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News Release 95-52

Primary Events in Photosynthesis Revealed

August 17, 1995

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Photosynthesis is the process by which the energy of sunlight is used by plants and bacteria to produce substances necessary to sustain life. The earliest events in this process in bacteria occur in less than a billionth of a second in pigmentprotein complexes called reaction centers (RCs). Two National Science Foundation (NSF)supported researchers at Washington University in St. Louis, Dewey Holten and Christine Kirmaier, have made a breakthrough in understanding these events at the molecular level.

"An understanding of the molecular mechanism of photosynthesis may enable scientists to mimic these processes in synthetic non-biological systems to transform light energy into chemical energy," says Stewart Hendrickson, program director of the molecular biophysics program at NSF, which supported the research.

In response to sunlight, electrons are transferred across the RC and thus across a membrane. This process occurs by way of only one of two pathways with very high efficiency. Although there is a similar arrangement of pigments in both pathways, it has been puzzling why one pathway is active while the other is inactive.

Holten and Kirmaier have genetically engineered an RC in which only two amino acids of the protein subunits have been changed. These changes have resulted in new properties of the RC. The results of their work are published in this week's issue of the journal Science.

The results shed light on the molecular mechanisms by which the initial events of photosynthesis occur. They represent an important breakthrough that will stimulate further experimental and theoretical studies. "Our recent findings should have a major impact on photosynthesis research, and should be of general interest in the important area of electron transfer processes," says Holten.


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Cheryl L. Dybas, NSF, (703) 292-8070, email:

The National Science Foundation (NSF) is an independent federal agency that supports fundamental research and education across all fields of science and engineering. In fiscal year (FY) 2018, its budget is $7.8 billion. NSF funds reach all 50 states through grants to nearly 2,000 colleges, universities and other institutions. Each year, NSF receives more than 50,000 competitive proposals for funding and makes about 12,000 new funding awards.

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