We report supramolecular quantum mechanics/molecular mechanics simulations on the peridinin–chlorophyll a protein (PCP) complex from the causative algal species of red tides. These calculations reproduce for the first time quantitatively the distinct peridinin absorptions, identify multichromophoric molecular excitations, and elucidate the mechanisms regulating the strongly allowed S₀ (1¹A_g^–) → S₂ (1¹B_u⁺) absorptions of the bound peridinins that span a 58 nm spectral range in the region of maximal solar irradiance. We discovered that protein binding site-imposed conformations, local electrostatics, and electronic coupling contribute equally to the spectral inhomogeneity. Electronic coupling causes coherent excitations among the densely packed pigments. Complementary pairing of tuning mechanisms is the result of a competition between pigment–pigment and pigment–environment interactions. We found that the aqueous solvent works in concert with the charge distribution of PCP to produce a strong correlation between peridinin spectral bathochromism and the local dielectric environment.

中文翻译：

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通过光合天线蛋白的均等贡献机制进行光收集。

我们报道了来自潮汐致病藻种的peridinin-叶绿素a蛋白（PCP）复合物的超分子量子力学/分子力学模拟。这些计算首次定量地再现了不同的peridinin吸收，确定了多发色分子的激发，并阐明了调节强烈允许的S ₀（1 ¹ A _g ^–）→S ₂（1 ¹ B _u ⁺）在最大太阳辐照度区域中跨越58 nm光谱范围的结合的Peridinin的吸收。我们发现蛋白质结合位点强加的构象，局部静电和电子耦合对光谱的不均匀性均具有相同的作用。电子耦合在紧密堆积的颜料之间引起相干激发。调节机制的互补配对是颜料-颜料与颜料-环境相互作用之间竞争的结果。我们发现，水性溶剂与PCP的电荷分布协同作用，从而在peridinin光谱红移和局部介电环境之间产生了很强的相关性。