TY - JOUR
T1 - Role of the Photosystem II as an Environment in the Oxidation Free Energy of the Mn Cluster from S1 to S2
AU - Takahashi, Hideaki
AU - Suzuoka, Daiki
AU - Sakuraba, Shun
AU - Morita, Akihiro
N1 - Funding Information:
We are grateful to Assoc. Prof. Y. Shibata at Tohoku University for fruitful discussion. This work was supported by the Grant-in-Aid for Scientific Research on Innovative Areas (No. 23118701) from the Ministry of Education, Culture, Sports, Science, and Technology (MEXT); the Grant-in-Aid for Challenging Exploratory Research (No. 25620004); and the Grant-in-Aid for Scientific Research(C) (No. 17K05138) from the Japan Society for the Promotion of Science (JSPS). The calculations were performed partly using computational resources of the HPCI systems provided by SX-ACE at Osaka University and at Tohoku University and Cray XC30 and XC40 at Kyoto University through the HPCI System Research Project (Project IDs: hp150131, hp160007, hp170046, and hp180032).
Publisher Copyright:
© 2019 American Chemical Society.
PY - 2019/8/22
Y1 - 2019/8/22
N2 - The manganese cluster (CaMn4O5) in the photosystem II (PSII) is the reaction center of the light-driven oxidation reaction, which generates the molecular oxygen. In this paper, we address the issue of the effect of the environment on the free energy associated with the oxidation of the Mn cluster in S1 state by conducting the large-scale quantum mechanical/molecular mechanical simulations, which involve the whole of the PSII monomer. It was found by the simulations at the level of the B3LYP functional that the environment surrounding the Mn cluster reduces the vertical oxidation free energy δμvrt by 64.8 kcal/mol. A decomposition analysis of the free energy δμvrt revealed that the system composed of peptide chains, ligands, lipids, and potassium ions contributes to lowering of δμvrt by -98.0 kcal/mol, whereas the solvent water makes an opposite contribution of 38.9 kcal/mol. Reduction of the vertical oxidation free energy directly leads to the lowering of the activation free energy δGac for the electron transfer reaction from the Mn cluster in S1 state to the neighboring Tyrz+. Consequently, the electron transfer rate was found to be enhanced by a factor of 1012 by virtue of the influence of the environment.
AB - The manganese cluster (CaMn4O5) in the photosystem II (PSII) is the reaction center of the light-driven oxidation reaction, which generates the molecular oxygen. In this paper, we address the issue of the effect of the environment on the free energy associated with the oxidation of the Mn cluster in S1 state by conducting the large-scale quantum mechanical/molecular mechanical simulations, which involve the whole of the PSII monomer. It was found by the simulations at the level of the B3LYP functional that the environment surrounding the Mn cluster reduces the vertical oxidation free energy δμvrt by 64.8 kcal/mol. A decomposition analysis of the free energy δμvrt revealed that the system composed of peptide chains, ligands, lipids, and potassium ions contributes to lowering of δμvrt by -98.0 kcal/mol, whereas the solvent water makes an opposite contribution of 38.9 kcal/mol. Reduction of the vertical oxidation free energy directly leads to the lowering of the activation free energy δGac for the electron transfer reaction from the Mn cluster in S1 state to the neighboring Tyrz+. Consequently, the electron transfer rate was found to be enhanced by a factor of 1012 by virtue of the influence of the environment.
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U2 - 10.1021/acs.jpcb.9b03831
DO - 10.1021/acs.jpcb.9b03831
M3 - Article
C2 - 31282160
AN - SCOPUS:85071707241
SN - 1520-6106
VL - 123
SP - 7081
EP - 7091
JO - Journal of Physical Chemistry B
JF - Journal of Physical Chemistry B
IS - 33
ER -