Future for artificial photosynthesis shines.

Is artificial photosynthesis possible? Might scientists someday mimic nature's sunlight-capturing molecular machinery in order to use solar energy for human purposes?

Based on recent work revealing the structure of key membrane proteins that enable plants and bacteria to harness the sun's energy, photosynthesis may become "the first complex biological system to have its structure, function, and regulation described in rigorous physical-chemical terms at the atomic level," say James Barber, a biochemist at the Imperial College of Science, Technology, and Medicine in London, and B. Andersson, a chemist at Stockholm University.

"Such knowledge could provide a blueprint for new technologies for the production of energy," they write in the July 7 NATURE.

Specifically, the scientists herald recent work showing the structure of a "light-harvesting pigment protein," an advance that they say could eventually make possible artificial photosynthesis. This light-harvesting pigment protein lets photosynthetic organisms take advantage of the entire solar spectrum and grow where little light shines. By means of a new technique called electron crystallography, scientists can view the structure of the light-harvesting chlorophyll a/b-protein complex, also known as LHCII.

The most abundant membrane protein in chloroplasts, where photosynthesis occurs, LHCII binds about half of all chlorophyll, the researchers say. Organisms able to harvest light in this way can survive continual and unpredictable fluctuations in sunlight. Within seconds of a slight shift in clouds, sunlight can vary by up to 100 times in intensity. Thus, chemical mechanisms are crucial in regulating light absorption and restoring interrupted photosynthesis.

In recent months, an artificial photochemical system has generated for the first time a "spin-polarized triplet state"--a charge-transfer reaction previously seen only in live photosynthetic organisms. In another key advance, a group has synthesized self-assembling proteins genetically engineered to incorporate specialized pigments.

The "secrets of the molecular electronics" of photosynthesis will soon become available for solar energy conversion, Barber and Andersson predict. "The challenge now is to devise an artificial system based on this knowledge."