Computational Analysis of the Light-induced Electron Transfer Reactions in Photosynthetic Reaction Centers

Abstract

Atmospheric oxygen is generated by water oxidation at the MnCa cluster of the protein-pigment complex, photosystem II located in the thylakoid membrane. At the heart of photosynthetic reaction centers (RCs) are pairs of chlorophylla, P680 in photosystem II and P700 in photosystem I of cyanobacteria, algae, or plants, and a pair of bacteriochlorophylla, P870 in purple bacterial RCs. These pairs differ greatly in their redox potentials for one-electron oxidation, E_m. For P680, E_m is 1100-1200 mV, but for P700 and P870, E_m is only 500 mV. Calculations with the linearized Poisson-Boltzmann equation reproduce these measured E_m differences successfully.