Mechanism of Charge Separation in Purple Bacterial Reaction Centers

Abstract

This chapter discusses the pathway, kinetics and energetics of the initial electron-transfer steps in reaction centers (RCs) from purple photosynthetic bacteria. We consider the unusual dependence of the kinetics on temperature, the strong specificity of the reactions for electron acceptors on the A side of the RC, effects of vibrational wavepackets, the multiphasic nature of the kinetics, effects of mutations and pigment substitutions, and links between the kinetics of electron transfer and vibrational equilibration. We then discuss some of the theories that have been used to rationalize the dynamics and temperature dependence of the electron-transfer reactions, including Marcus theory, coupling to quantized vibrational modes and density-matrix treatments. Our discussion illustrates the power of microscopic simulations for connecting structural information with mechanistic interpretations.