Development of Molecular Dynamics Parameters and Theoretical\nAnalysis of Excitonic and Optical Properties in the Light-Harvesting\nComplex II

The light-harvesting\ncomplex II (LHCII) in green plants exhibits\nhighly efficient excitation energy transfer (EET). A comprehensive\nunderstanding of the EET mechanism in LHCII requires quantum chemical,\nmolecular dynamics (MD), and statistical mechanics calculations that\ncan adequately describe pigment molecules in heterogeneous environments.\nHerein, we develop MD simulation parameters that accurately reproduce\nthe quantum mechanical/molecular mechanical energies of both the ground\nand excited states of all chlorophyll (Chl) molecules in membrane\nembedded LHCII. The present simulations reveal that Chl <i>a</i> molecules reside in more inhomogeneous environments than Chl <i>b</i> molecules. We also find a narrow gap between the exciton\nenergy levels of Chl <i>a</i> and Chl <i>b</i>. In addition, we investigate the nature of the exciton states of\nChl molecules, such as delocalization, and analyze the optical spectra\nof LHCII, which align with experimental results. Thus, the MD simulation\nparameters developed in this study successfully reproduce the excitonic\nand optical properties of the Chl molecules in LHCII, validating their\neffectiveness.