| Photosystem I (PSI) and II (PSII) possess chlorophyll pairs P~A~/P~B~ and P~D1~/P~D2~, respectively. These chlorophylls are the primary electron donors in the light-induced electron transfer. After the electron transfer, the radical cation remains on these chlorophyll pairs, forming [P~A~/P~B~]^·+^ and [P~D1~/P~D2~]^·+^. The positive charge distributions over the two chlorophylls were reported to be 10/90-50/50 for P~A~^·+^/P~B~^·+^ [1,2] and 70/30-80/20 for P~D1~^·+^/P~D2~^·+^ [3,4]. To clarify the origin of the distributions, we calculated ratios of P~A~^·+^/P~B~^·+^ and P~D1~^·+^/P~D2~^·+^ with a quantum mechanical/molecular mechanical (QM/MM) approach and the... |
