BERKELEY, CA -- Through photosynthesis, green plants and cyanobacteria are able to transfer sunlight energy to molecular reaction centers for conversion into chemical energy with nearly 100-percent efficiency. Speed is the key - the transfer of the solar energy takes place almost instantaneously so little energy is wasted as heat. How photosynthesis achieves this near instantaneous energy transfer is a long-standing mystery that may have finally been solved.
A study led by researchers with the U.S. Department of Energys Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) at Berkeley reports that the answer lies in quantum mechanical effects. Results of the study are presented in the April 12, 2007 issue of the journal Nature.
"We have obtained the first direct evidence that remarkably long-lived wavelike electronic quantum coherence plays an important part in energy transfer processes during photosynthesis," said Graham Fleming, the principal investigator for the study. This wavelike characteristic can explain the extreme efficiency of the energy transfer because it enables the system to simultaneously sample all the potential energy pathways and choose the most efficient one.
Fleming is the Deputy Director of Berkeley Lab, a professor of chemistry at UC Berkeley, and an internationally acclaimed leader in spectroscopic studies of the photosynthetic process. In a paper entitled, Evidence for wavelike energy transfer through quantum coherence in photosynthetic systems, he and his collaborators report the detection of quantum beating signals, coherent electronic oscillations in both donor and acceptor molecules, generated by light-induced energy excitations, like the ripples formed when stones are tossed into a pond.
Electronic spectroscopy measurements made on a femtosecond (millionths of a billionth of a second) time-scale showed these oscillations meeting and interfering constructivel
Contact: Lynn Yarris
DOE/Lawrence Berkeley National Laboratory