( Too much sun ?for plants as well as peo...)How plants avoid feeling the burn

"We knew that biomolecules called carotenoids participate in this process of photoprotection, but the question has been, how does this work?" said Iris Visoly-Fisher, a postdoctoral research associate in the Biodesign Institute at Arizona State University.

Carotenoids act as 'wires' to carry away the extra sunlight energy in the form of unwanted electrons, somehow wicking away the extra electrons across long distances from locations that could damage plant tissues and photosynthesis. During photoprotection, the consensus school of thought was that carotenoids--the source of the orange pigments in carrots and Vitamin A -- become oxidized, or charged, losing an electron in the process.

Now, Fisher and other ASU scientists have found a way to measure for the first time the electrical conductance within such an important biomolecule. And in doing so, the team has produced a new discovery which shatters the prevailing view. The research team found that oxidation is not required for photoprotection, but rather, carotenoids in a neutral, or uncharged state, can readily handle the electron overload from the sun.

Their findings have been published in the prestigious journal Proceedings of the National Academy of Sciences (PNAS) under the title"Conductance of a Biomolecular Wire" (http://www.pnas.org/cgi/content/abstract/0600593103v1).

"This is a remarkable experimental tour-de-force and the result is quite unexpected," said Lindsay, who directs Fisher's work in the Biodesign Institute's Center for Single Molecule Biophysics. "Carotene was regarded as the poster child for this molecula
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Source:Arizona State University