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Japan research on photosynthetic process paves way for artificial conversions

The protein composites that produce oxygen molecules are seen in a state in which two are bonded together. The circular section includes the "distorted chair" structure that encourages the process. (Image provided by Okayama University)

OSAKA -- The process by which plants break down water into oxygen as part of photosynthesis has been discovered, according to the results of work by a team of researchers at Okayama University and other institutions, who published their findings on Oct. 18.

It was understood that the process was governed by composites created from about 20 proteins, but how the conversion is carried out remained unknown until now. The team says that its work has provided important data for work toward making artificial photosynthesis a reality.

Photosynthesis, which uses sunlight to convert water and carbon dioxide into oxygen and starch, is split into a number of responsive processes. First, the protein composites remove electrons and hydrogen ions from two water molecules, and then create oxygen molecules.

Team member Jian-Ren Shen, a professor at Okayama University, and others had already been the first in the world to uncover the structure of the composites, but the process to create oxygen had been unknown.

The team successfully used very short X-ray bursts to observe the three middle phases in the five step process to break down water molecules into oxygen molecules. They said that they found the point where the reaction took place had atoms from manganese, calcium and other elements arranged in a shape like a distorted chair that changes to more easily facilitate bonding a pair of oxygen atoms.

With the process clarified, it may be possible to employ similar processes of breaking down water with solar light and artificially yield a reaction to create useful chemical substances.

Michihiro Suga, an associate professor at Okayama University and a member of the team behind the research, said, "We've come closer to the essence of the process to break down water in photosynthesis. We want to find a way to emulate the reactions taking place inside plants."

Their findings were published in the electronic edition of the American scientific journal Science on Oct. 18.

(Japanese original by Ryo Watanabe, Osaka Science & Environment News Department)

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