光系統 II 核心複合體能量傳遞動力學的理論研究

Abstract

The Photosystem II (PSII) core complex, the engine for oxygen genera- tion, is an important photosynthetic complex. It is a symmetric dimer that contains four antenna complexes (CP43 and CP47) and two reaction cen- ters (RCs). Understanding energy transport in such complex photosynthetic complexes requires theoretical effective models that can faithfully reproduce excitation energy transfer (EET) dynamics. In this work, we present an effec- tive model for EET in the PSII core complex based on a previous molecular dynamics (MD) simulation study. This model describes absorption spectra of CP47, CP43 and RC at 297 K as well as the full EET dynamics among the 74 chromophores in the PSII. Energy transfer rate constants are modeled based on the modified Redfield theory and two pathways of primary charge separation are treated phenomenologically in our model. We show that in the monomer, EET between two antenna complexes most likely occurs presum- ably through the RC. Also, the CLA625s are a bridge between monomers and cause the CP47s to become an energy regulator, which can transfer the excitation energy between monomers and maintain high efficiency of charge transfer when one of RCs is closed. CP47s as an energy regulator may be the reason for the dimeric structure of PSII core complex. Our model provides new insights towards the understanding of light harvesting in the PSII core complex and shows that a first principle approach based on MD simulations and quantum chemistry calculations can be effectively utilized to elucidate the dynamics of light harvesting in photosynthetic complexes.