Magazine article Science News

Shedding Light on Photosynthesis

Magazine article Science News

Shedding Light on Photosynthesis

Article excerpt

Shedding light on photosynthesis

Scientists have succeeded in using genetic engineering to study the first steps of photosynthesis, an achievement that should speed understanding of how plants and bacteria change light energy to chemical energy.

The researchers used recombinant DNA technology to change a specific amino acid in a protein that forms part of the "reaction center" where photosynthesis begins in bacteria. The method allows scientists to tinker with a few key parts of the reaction center and then use ultrafast lasers to analyze how these changes affect photosynthesis, they report in the October PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES (Vol.85, No.20).

The reaction center for photosynthesis is an elaborate protein cage holding other molecules, including chlorophyll, in such a way that lightenergized electrons pass along these molecules, known as prosthetic groups. Usually, incoming light energizes a pair of chlorophyll molecules so that they pass on an electron to a close relative of chlorophyll called a pheophytin, which passes the electron to a molecule called a quinone. The movement of the negatively charged electron causes a separation of positive and negative charges in the reaction center, creating an electrochemical potential that can power reactions in other cell parts.

In the engineered protein, the researchers altered the primary link between the protein and one of the chlorophylls so the chlorophyll lost a magnesium atom and became a pheophytin. This changed the chemistry of the reaction center, but it still functioned at about half its original efficiency, report Douglas C. …

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