Erlangen 2022 – wissenschaftliches Programm

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MO: Fachverband Molekülphysik

MO 3: Electronic I

MO 3.3: Vortrag

Montag, 14. März 2022, 17:15–17:30, MO-H5

Chlorophyll Excitation in Photosystem 1 Tuned by the Protein Environment: Insights from Fully Atomistic QM/MM — •Sebastian Reiter, Ferdinand Kiss, and Regina de Vivie-Riedle — Department Chemie, Ludwig-Maximilians-Universität München, München

Photosystem 1 (PS1) is one of the most efficient natural light-harvesting systems. Energy is absorbed by an antenna complex of chlorophylls and transferred to a reaction core, where it drives one of the fundamental redox processes of photosynthesis. Understanding the high efficiency of PS1 requires an accurate evaluation of the chlorophyll absorption energies, affected by their natural environment (site energies). However, this is challenging because not only the full electrostatic environment but also dynamic effects must be taken into account. In this work, we present accurate site energies of all 96 chlorophylls in the asymmetric unit of PS1 in S. elongatus. Therefore, we constructed a fully atomistic model of the trimeric PS1 complex in a solvated lipid membrane to describe the environment as thoroughly as possible. With this extensive structural model, we sampled geometries from classical trajectories and calculated site energies for each chlorophyll with the high-level DFT/MRCI method in a QM/MM scheme. Our results identify dynamic energy sinks in the antenna complex and reveal a fundamental asymmetry in the reaction center. Moreover, we are able to separate the environmental influence into the electrostatic interaction of the chlorophyll with its surroundings and the structural constraints imposed by neighboring residues.