期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2006
卷号：103
期号：26
页码：9855-9860
DOI：10.1073/pnas.0601446103
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：At the heart of photosynthetic reaction centers (RCs) are pairs of chlorophyll a (Chla), P700 in photosystem I (PSI) and P680 in photosystem II (PSII) of cyanobacteria, algae, or plants, and a pair of bacteriochlorophyll a (BChla), P870 in purple bacterial RCs (PbRCs). These pairs differ greatly in their redox potentials for one-electron oxidation, Em. For P680, Em is 1,100-1,200 mV, but for P700 and P870, Em is only 500 mV. Calculations with the linearized Poisson-Boltzmann equation reproduce these measured Em differences successfully. Analyzing the origin for these differences, we found as major factors in PSII the unique Mn4Ca cluster (relative to PSI and PbRC), the position of P680 close to the luminal edge of transmembrane {alpha}-helix d (relative to PSI), local variations in the cd loop (relative to PbRC), and the intrinsically higher Em of Chla compared with BChla (relative to PbRC).
关键词：electron transfer ; photosystem ; redox potential ; special pair ; electrostatic energy
