Reaction Center Excitation in Photosystem II: From Multiscale Modeling to Functional Principles

Abstract

Identif ication of charge-transfer states implicated in far-red light-driven charge separation, which can be activated in a conformation-and wavelength-dependent manner.

A Vision for the Future of Multiscale Modeling

“…Over the years, Photosystem-II (PSII), a large membrane protein, has served as an optimal model to assess the predictive capabilities of many computational methods, ,,,− directly comparing them with the huge amount of available experimental data. ,,, PSII functions as a positive/negative charge separation engine. The reaction scheme consists of funneling light-induced excited states into one part of the large reaction center, where the primary charge separation occurs.…”

Excitation landscape of the CP43 photosynthetic antenna complex from multiscale simulations

“…109 Stark spectroscopy and more recent computational studies on another light harvesting protein, the PSI-Lhca4 complex demonstrated that a distinctive red-shied emission originates from the mixing of the lowest exciton state with a CT state of an excitonically coupled dimer. 110 Intermolecular charge-transfer (CT) states among photosynthetic pigments (Chl D1 + Pheo D1 − or P D1 + Pheo D1 − ) directly control primary charge separation and charge recombination processes in the PSII-RC, 26,63,65 but the presence of CT states in CP43 or CP47 core antenna proteins of PSII has not been reported. The present TD-DFT calculations on Chl dimers enable us to approach this question for the case of CP43.…”

“…Such dynamic evolution of CT character has also been demonstrated in the lowenergy excitation prole of RC pigments. 26,62,64,65 The C2-C10 dimer is not the only Chl pair in CP43 to possess a CT state; our results locate higher-energy excited states (above 3 eV) with pure CT character for the C9-C11, C9-C10, C8-C10, C10-C11 pairs (Table S6 †), however the C2-C10 pair is unique in having a very low-lying CT state, essentially interleaved with the lowest locally excited states of the whole system.…”

Contributions of PD1 and PD2 to the [PD1PD2]+-minus-[PD1PD2] difference spectrum in the Soret region in Photosystem II

“…A few picoseconds after the excitation reaches Chl D1 , a charge separation occurs resulting in the formation of the Chl D1 + Phe D1 − and then of the [P D1 P D2 ] + Phe D1 − radical pair states, with the positive charge mainly located on P D1 , e.g . (Holzwarth et al 2006, Romero et al 2017, Sirohiwal and Pantazis 2023). After the formation of [P D1 P D2 ] + Phe D1 − , the electron on Phe D1 − is transferred to Q A , the primary quinone electron acceptor, and then to Q B , the second quinone electron acceptor.…”

“…(Mirkovic et al 2017) for a review, with 4 Chl- a molecules, P D1 , P D2 , Chl D1 , Chl D2 and 2 Phe- a molecules, Phe D1 and Phe D2 , e.g . (Cardona et al 2012, Holzwarth et al 2006, Sirohiwal and Pantazis 2023, Romero et al 2017, Yoneda et al 2022).…”