9/24/97
Contacts:
Curtis W. Hoganson, Chemistry
(517) 355-9715, Extension 260
Gerald T. Babcock, Chemistry
(517) 355-9715, Extension 346
Tom Oswald, Media Communications
(517) 355-2281
EMBARGOED FOR RELEASE 4 P.M. (EDT) THURSDAY, SEPT. 25
MSU RESEARCH SHEDS NEW LIGHT ON PHOTOSYNTHESIS
EAST LANSING, Mich. -- The process of photosynthesis -- the way in which plants convert water and carbon dioxide into oxygen -- is much clearer now, thanks to research by two Michigan State University chemists.
The work of Curtis W. Hoganson, a research associate in MSU's Department of Chemistry, and Gerald T. Babcock, chemistry department chairperson, is detailed in the Sept. 26 issue of the journal Science.
While other researchers have been able to hit upon only "bits and pieces" of the process, Hoganson and Babcock were able to bring it all together.
"This whole thing has been pretty mysterious," Babcock said. "Other proposals have just been able to touch upon bits and pieces of it. We feel that this is the first description of the molecular mechanism for the process that is on the mark."
Because of the intricacies of the process, scientists have not been able to reproduce, in a laboratory setting, the conversion of water to oxygen that occurs in photosynthesis. By describing the chemical process by which this happens, a new world of discoveries could await.
"By identifying a new chemical mechanism for a rather difficult transformation," Hoganson said, "we are giving synthetic chemists a good idea of what needs to be present in an artificial catalyst in order to convert water to oxygen."
The long-term implications of the work are many, the researchers said. For example, it could lead to a much more efficient way of solar energy conversion.
At present, a cheap, plentiful source of hydrogen atoms that can be used in solar energy conversion systems is not available. Water fills the bill ideally as this hydrogen-atom source.
The insights generated by the MSU researchers into the way in which photosynthesis operates may enable others to synthesize chemical systems that unlock the tremendous potential of water for effective solar energy conversion. Such a development would provide energy benefits worldwide and beyond.
"It could have utility in systems designed to generate oxygen from water," Hoganson said, "which might be useful in a space station."
Among the myriad problems the Mir Space Station has faced was a temporary malfunction of its oxygen generators.
Another potential benefit of the work is a better understanding of how crops grow.
"When plants don't get enough water and receive too much direct sunlight, the obvious result is death," Babcock said. "Having a better handle on how photosynthesis works and, particularly, how the water chemistry takes place, could benefit farmers facing drought conditions."
The new model for how plants use light to remove four hydrogens from two water molecules to make a molecule of oxygen grew out of the realization that the essential plant co-factors for this process operate in a matter analogous to those in several other enzymes, Babcock said.
In the plant, an amino acid known as tyrosine and four atoms of manganese are at the heart of the water-conversion process. When light is absorbed by the plant, the energy is transferred first to chlorophyll and then to tyrosine, which uses it to remove a hydrogen from one of two water molecules associated with the manganese ions. This relatively simple process is repeated four times to finally produce the oxygen.
This mode of operation of the photosynthetic process is remarkably similar to the way that metal ions and amino acids work together in a number of other enzymes, including the proteins that are involved in DNA synthesis and in the processes that are inhibited by aspirin.
This aspect of the mechanism for water oxidation, that is its underlying similarity to other enzymes, was a surprising realization, Babcock and Hoganson said.
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