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Scientists swap key metal necessary for turning sunlight into chemical energy.

Byline: ANI

Washington, May 12 (ANI): A large collaboration between various universities in the US has come up with a surprising twist to photosynthesis by swapping a key metal necessary for turning sunlight into chemical energy.

In the heart of every green leaf are pigments called chlorophyll, which not only give most plants their color, but also along with the yellow and orange carotenoid pigments, are key molecules that harvest light across the spectrum.

In all plant chlorophylls, only one particular metal, magnesium, is held tightly within the molecule's center.

During photosynthesis, plants have two photosystems that work in tandem: photosystem I and photosystem II.

To peer at the inner workings of photosynthesis, the team used a hardy, well-studied, photosynthetic bacterium called Rhodobacter sphaeroides.

An organism similar to this purple bacterium was likely one of the earliest photosynthetic bacteria to evolve.

The center stage of photosynthesis is the reaction center, where light energy is funneled into specialized chlorophyll binding proteins.

"One of our research strategies is to introduce mutations into the bacteria and study how these affect the energy conversion efficiency of the reaction center," said Su Lin, senior researcher at ASU's Department of Chemistry and Biochemistry and Biodesign Institute, and lead author of the study.

"Carefully-designed aberrations provide extensive information about the normal mechanism of energy conversion in reaction centers, just like studying a disease clarifies the parameters of health for the involved biochemical pathways and tissues. From this, we can learn a lot about the most basic mechanisms of photosynthesis," she added.

The reactions that convert light to chemical energy happen in a millionth of a millionth of a second, which makes experimental observation extremely challenging.

A premier ultrafast laser spectroscopic detection system that Lin has built, with the sponsorship of the National Science Foundation, acts like a high-speed motion picture camera.

It splits the light spectrum into infinitesimally discrete slivers, allowing the group to capture vast numbers of ultrafast frames from the components of these exceedingly rapid reactions.

These frames are then mathematically assembled, allowing the group to make a figurative 'movie' of the energy transfer events of photosynthesis.

"The electron transfer driving force can be determined by either the properties of the metal cofactors themselves or through their interaction with the protein," said Lin. In the case of the zinc reaction center, the driving force is regulated through the coordination of the metal," she added.

The results may enable researchers to explore a deeper understanding of the structure, function, and evolution of photosynthesis reaction centers in photosystems I and II. (ANI)

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Publication:Asian News International
Date:May 12, 2009
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