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Title: Multiscale QM/MM molecular dynamics simulations of the trimeric major light-harvesting complex II
Authors: Maity, Sayan 
Daskalakis, Vangelis 
Elstner, Marcus 
Kleinekathöfer, Ulrich 
Major Field of Science: Natural Sciences
Field Category: Chemical Sciences
Keywords: Chlorophyll;Degrees of freedom (mechanics);Digital storage;Excited states;Excitons;Ground state;Harvesting;Light;Machinery;Molecular modeling;Molecules;Quantum theory;Quenching;Spectral density
Issue Date: 28-Mar-2021
Source: Physical Chemistry Chemical Physics, 2021, vol. 23, no. 12, pp. 7407 - 7417
Volume: 23
Issue: 12
Start page: 7407
End page: 7417
Journal: Physical Chemistry Chemical Physics 
Abstract: Photosynthetic processes are driven by sunlight. Too little of it and the photosynthetic machinery cannot produce the reductive power to drive the anabolic pathways. Too much sunlight and the machinery can get damaged. In higher plants, the major Light-Harvesting Complex (LHCII) efficiently absorbs the light energy, but can also dissipate it when in excess (quenching). In order to study the dynamics related to the quenching process but also the exciton dynamics in general, one needs to accurately determine the so-called spectral density which describes the coupling between the relevant pigment modes and the environmental degrees of freedom. To this end, Born-Oppenheimer molecular dynamics simulations in a quantum mechanics/molecular mechanics (QM/MM) fashion utilizing the density functional based tight binding (DFTB) method have been performed for the ground state dynamics. Subsequently, the time-dependent extension of the long-range-corrected DFTB scheme has been employed for the excited state calculations of the individual chlorophyll-a molecules in the LHCII complex. The analysis of this data resulted in spectral densities showing an astonishing agreement with the experimental counterpart in this rather large system. This consistency with an experimental observable also supports the accuracy, robustness, and reliability of the present multi-scale scheme. To the best of our knowledge, this is the first theoretical attempt on this large complex system is ever made to accurately simulate the spectral density. In addition, the resulting spectral densities and site energies were used to determine the exciton transfer rate within a special pigment pair consisting of a chlorophyll-a and a carotenoid molecule which is assumed to play a role in the balance between the light harvesting and quenching modes.
ISSN: 1463-9084
DOI: 10.1039/d1cp01011e
Rights: © Owner Societies
Attribution-NonCommercial-NoDerivatives 4.0 International
Type: Article
Affiliation : Jacobs University Bremen 
Cyprus University of Technology 
Karlsruhe Institute of Technology 
Appears in Collections:Άρθρα/Articles

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