BERKELEY, CA -- About 3.2 billion years ago, primitive bacteria developed a way to harness sunlight to split water molecules into protons, electrons and oxygen, the cornerstone of photosynthesis that led to atmospheric oxygen and more complex forms of life -- in other words, the world and life as we know it.
Today, scientists have taken a major step toward understanding this process by deriving the precise structure of a catalyst composed of four manganese atoms and one calcium atom that drives this water-splitting reaction. Their work, detailed in the Nov. 3, 2006 issue of the journal Science, could help researchers synthesize molecules that mimic this catalyst, which is a central focus in the push to develop clean energy technologies that rely on sunlight to split water and form hydrogen to feed fuel cells or other non-polluting power sources.
Specifically, an international team led by scientists from the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) pieced together high-resolution (approximately 0.15 ngstrom) structures of a Mn4Ca cluster found in a photosynthetic protein complex (one ngstrom equals one ten-billionth of a meter). The team, which includes scientists from Germany's Technical and Free Universities in Berlin, the Max Planck Institute in Mlheim, and the Stanford Synchrotron Radiation Laboratory, used an innovative combination of x-ray spectroscopy and protein crystallography to yield the highest-resolution structures yet of the metal catalyst.
"This is the first study to combine x-ray absorption spectroscopy and crystallography in such a detailed manner to determine the structure of an active metal site in a protein, especially something as complicated as the photosynthetic Mn4Ca cluster," says Junko Yano of Berkeley Lab's Physical Biosciences Division, who is one of the lead authors of the study.
The metal catalyst resides in a large protein complex, called photosystem II
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Contact: Dan Krotz
dakrotz@lbl.gov
510-486-4019
DOE/Lawrence Berkeley National Laboratory
3-Nov-2006