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：2020
卷号：117
期号：28
页码：16373-16382
DOI：10.1073/pnas.2000895117
出版社：The National Academy of Sciences of the United States of America
摘要：In photosynthetic reaction centers from purple bacteria (PbRC) and the water-oxidizing enzyme, photosystem II (PSII), charge separation occurs along one of the two symmetrical electron-transfer branches. Here we report the microscopic origin of the unidirectional charge separation, fully considering electron–hole interaction, electronic coupling of the pigments, and electrostatic interaction with the polarizable entire protein environments. The electronic coupling between the pair of bacteriochlorophylls is large in PbRC, forming a delocalized excited state with the lowest excitation energy (i.e., the special pair). The charge-separated state in the active branch is stabilized by uncharged polar residues in the transmembrane region and charged residues on the cytochrome c 2 binding surface. In contrast, the accessory chlorophyll in the D1 protein (Chl D1 ) has the lowest excitation energy in PSII. The charge-separated state involves Chl D1 • and is stabilized predominantly by charged residues near the Mn 4 CaO 5 cluster and the proceeding proton-transfer pathway. It seems likely that the acquirement of water-splitting ability makes Chl D1 the initial electron donor in PSII.
关键词：unidirectional electron transfer ; oxygen evolution ; P680 ; excitation energy transfer ; artificial photosynthesis
