A theoretical analysis of absorption spectra and dynamics of photosynthetic reaction centers

In this work, we construct a microscopic model with which one can reconstruct all the experimentally observed characteristics of the RCs including temperature effects. For this purpose, we analyze the absorption spectra of Rb. sphaeroides RCs (R26 and R26.Phe-a mutants). We apply the excitonic-vibronic model with the displaced harmonic potential surface model for the nuclear freedoms and determine microscopic properties such as the electronic coupling constants, the vibrational frequencies, and the displacements among the potential surfaces of these electronic states. We also take into account inhomogeneity of RCs in our theoretical analysis. We introduce a thermal expansion model to treat temperature dependent peak shifts observed in the P band of the absorption spectra of the RCs. With the resulting information, we also calculate the rate constants of the dynamic processes occurring in RCs, determining the electronic coupling constants among the electronic states involved in electron transfer and electronic energy transfer of the RCs. Based on the excitonic-vibronic model, we also investigate the mechanism of the direct path PB*H --> P+B-H recently observed in YM210W mutant.