TY - JOUR
T1 - Primary charge separation within the structurally symmetric tetrameric Chl2APAPBChl2B chlorophyll exciplex in photosystem I
AU - Cherepanov, Dmitry A.
AU - Shelaev, Ivan V.
AU - Gostev, Fedor E.
AU - Petrova, Anastasia
AU - Aybush, Arseniy V.
AU - Nadtochenko, Victor A.
AU - Xu, Wu
AU - Golbeck, John H.
AU - Semenov, Alexey Yu
N1 - Publisher Copyright:
© 2021 Elsevier B.V.
PY - 2021/4
Y1 - 2021/4
N2 - In Photosystem I (PS I), the role of the accessory chlorophyll (Chl) molecules, Chl2A and Chl2B (also termed A-1A and A-1B), which are directly adjacent to the special pair P700 and fork into the A- and B-branches of electron carriers, is incompletely understood. In this work, the Chl2A and Chl2B transient absorption ΔA0(λ) at a time delay of 100 fs was identified by ultrafast pump-probe spectroscopy in three pairs of PS I complexes from Synechocystis sp. PCC 6803 with residues PsaA-N600 or PsaB-N582 (which ligate Chl2B or Chl2A through a H2O molecule) substituted by Met, His, and Leu. The ΔA0(λ) spectra were quantified using principal component analysis, the main component of which was interpreted as a mutation-induced shift of the equilibrium between the excited state of primary donor P700⁎ and the primary charge-separated state P700+Chl2−. This equilibrium is shifted to the charge-separated state in wild-type PS I and to the excited P700 in the PS I complexes with the substituted ligands to the Chl2A and Chl2B monomers. The results can be rationalized within the framework of an adiabatic model in which the P700 is electronically coupled with the symmetrically arranged monomers Chl2A and Chl2B; such a structure can be considered a symmetric tetrameric exciplex Chl2APAPBChl2B, in which the excited state (Chl2APAPBChl2B)* is mixed with two charge-transfer states P700+Chl2A− and P700+Chl2B−. The electron redistribution between the two branches in favor of the A-branch apparently takes place in the picosecond time scale after reduction of the Chl2A and Chl2B monomers.
AB - In Photosystem I (PS I), the role of the accessory chlorophyll (Chl) molecules, Chl2A and Chl2B (also termed A-1A and A-1B), which are directly adjacent to the special pair P700 and fork into the A- and B-branches of electron carriers, is incompletely understood. In this work, the Chl2A and Chl2B transient absorption ΔA0(λ) at a time delay of 100 fs was identified by ultrafast pump-probe spectroscopy in three pairs of PS I complexes from Synechocystis sp. PCC 6803 with residues PsaA-N600 or PsaB-N582 (which ligate Chl2B or Chl2A through a H2O molecule) substituted by Met, His, and Leu. The ΔA0(λ) spectra were quantified using principal component analysis, the main component of which was interpreted as a mutation-induced shift of the equilibrium between the excited state of primary donor P700⁎ and the primary charge-separated state P700+Chl2−. This equilibrium is shifted to the charge-separated state in wild-type PS I and to the excited P700 in the PS I complexes with the substituted ligands to the Chl2A and Chl2B monomers. The results can be rationalized within the framework of an adiabatic model in which the P700 is electronically coupled with the symmetrically arranged monomers Chl2A and Chl2B; such a structure can be considered a symmetric tetrameric exciplex Chl2APAPBChl2B, in which the excited state (Chl2APAPBChl2B)* is mixed with two charge-transfer states P700+Chl2A− and P700+Chl2B−. The electron redistribution between the two branches in favor of the A-branch apparently takes place in the picosecond time scale after reduction of the Chl2A and Chl2B monomers.
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U2 - 10.1016/j.jphotobiol.2021.112154
DO - 10.1016/j.jphotobiol.2021.112154
M3 - Article
C2 - 33636482
AN - SCOPUS:85101221129
SN - 1011-1344
VL - 217
JO - Journal of Photochemistry and Photobiology B: Biology
JF - Journal of Photochemistry and Photobiology B: Biology
M1 - 112154
ER -