AN ELECTRON-TRANSFER SWITCH IN PHOTOSYNTHETIC REACTION CENTRA

A detailed molecular mechanism of a conformational switch of electron transfer is derived from studies of conformational states and electronic structure in the reaction center of the photosynthetic bacterium Rhodopseudomonas viridis. This type of mechanism accounts for the observed temperature dependence of electron transfer from cytochrome c to the photoionized special pair of bacteriochlorophylls in the reaction center of several photosynthetic bacteria and thereby provides an alterative interpretation to the vibronic coupling and parallel path models. The mechanism also has interesting implications for electron gating in biological energy transduction, coupling of electron and proton transfer, the role of bridging aromatic amino acids in electron transfer, and molecular electronic devices.