TY - JOUR

T1 - A Multireference View of Photosynthesis

T2 - Uncovering Significant Site Energy Variations among Isolated Photosystem II Reaction Center Chlorophylls

AU - Sørensen, Lea Northcote

AU - De Vico, Luca

AU - Hansen, Thorsten

N1 - Funding Information: This work was supported financially by the Independent Research Fund Denmark (L.N.S. and T.H.). L.D.V. acknowledges financial support provided by MIUR (Ministero dell’Istruzione, dell’Università e della Ricerca) grant “Dipartimento di Eccellenza 2018–2022”. Publisher Copyright: © 2024 The Authors. Published by American Chemical Society.

PY - 2024

Y1 - 2024

N2 - Oxygenic photosynthesis begins in the reaction center (RC) of the protein complex photosystem II (PSII). PSII has an intriguing, nearly symmetrical arrangement of cofactors within its RC. Despite this symmetry, evolution has favored only one of the two branches of PSII for efficient electron transfer. Current spectroscopic experiments explore the electronic dynamics during the picoseconds after energy has entered the RC and until the electron transfers to the pheophytin of the first branch. We present state-of-the-art multiconfigurational multireference calculations of the excitation energies or site energies of the four chlorophyll pigments of the RC without protein environment considerations. We see a significant variation that breaks the apparent symmetry of the RC. The inner chlorophyll of the productive RC branch possessed the lowest excitation energy of the four central chlorophylls. Our computational method used here is expensive; thus, geometry optimization of the crystal structure is currently not possible. In future work, charge and energy dynamics within the RC will be included as well as a dynamic description of the protein environment and its coupling to the RC. Other state-of-the-art studies of the RC, at lower levels of electronic structure, include a static treatment of the protein environment. These almost unanimously report that the outer chlorophyll of the active branch had the lowest excitation energy. Future work is needed to reconcile this discrepancy.

AB - Oxygenic photosynthesis begins in the reaction center (RC) of the protein complex photosystem II (PSII). PSII has an intriguing, nearly symmetrical arrangement of cofactors within its RC. Despite this symmetry, evolution has favored only one of the two branches of PSII for efficient electron transfer. Current spectroscopic experiments explore the electronic dynamics during the picoseconds after energy has entered the RC and until the electron transfers to the pheophytin of the first branch. We present state-of-the-art multiconfigurational multireference calculations of the excitation energies or site energies of the four chlorophyll pigments of the RC without protein environment considerations. We see a significant variation that breaks the apparent symmetry of the RC. The inner chlorophyll of the productive RC branch possessed the lowest excitation energy of the four central chlorophylls. Our computational method used here is expensive; thus, geometry optimization of the crystal structure is currently not possible. In future work, charge and energy dynamics within the RC will be included as well as a dynamic description of the protein environment and its coupling to the RC. Other state-of-the-art studies of the RC, at lower levels of electronic structure, include a static treatment of the protein environment. These almost unanimously report that the outer chlorophyll of the active branch had the lowest excitation energy. Future work is needed to reconcile this discrepancy.

U2 - 10.1021/acsomega.3c05331

DO - 10.1021/acsomega.3c05331

M3 - Journal article

C2 - 38343919

AN - SCOPUS:85182576817

VL - 9

SP - 5246−5254

JO - ACS Omega

JF - ACS Omega

SN - 2470-1343

IS - 5

ER -