School of Biological and Chemical Sciences, Queen Mary College, University of London, Mile End, Bancroft Road, London, E1 4NS, United Kingdom.
J Phys Chem B. 2013 Jun 27;117(25):7605-14. doi: 10.1021/jp4025848. Epub 2013 Jun 14.
Light-harvesting by the xanthophylls in the antenna of photosystem II (PSII) is a very efficient process (with 80% of the absorbed energy being transfer to chlorophyll). However, the efficiencies of the individual xanthophylls vary considerably, with violaxanthin in LHCII contributing very little to light-harvesting. To investigate the origin of the variation we used Time Dependent Density Functional Theory to model the Coulombic interactions between the xanthophyll 1(1)B(u)(+) states and the chlorophyll Soret band states in the LHCII and CP29 antenna complexes. The results show that the central L1 and L2 binding sites in both complexes favored close cofacial associations between the bound xanthophylls and chlorophyll a, implying efficient energy transfer, consistent with previously reported experimental evidence. Additionally, we found that the peripheral V1 binding site in LHCII did not favor close xanthophyll-chlorophyll associations, confirming observations that violaxanthin in LHCII is not an effective light-harvester. Finally, violaxanthin bound into the L2 site of the CP29 complex was found to be very strongly coupled to its neighboring chlorophylls.
聚光复合物 II（PSII）天线中的叶黄素进行光捕获是一个非常高效的过程（吸收的 80%的能量被转移到叶绿素中）。然而，各个叶黄素的效率差异很大，LHCII 中的紫黄质对光捕获的贡献非常小。为了研究这种变化的起源，我们使用含时密度泛函理论（Time Dependent Density Functional Theory）对 LHCII 和 CP29 天线复合物中的叶黄素 1(1)B(u)(+)态与叶绿素 Soret 带态之间的库仑相互作用进行了建模。结果表明，两个复合物中的中央 L1 和 L2 结合位点都有利于结合态叶黄素与叶绿素 a 之间的紧密共面关联，这意味着能量转移效率较高，与之前报道的实验证据一致。此外，我们发现 LHCII 中的外周 V1 结合位点不利于叶黄素-叶绿素的紧密结合，证实了 LHCII 中的紫黄质不是有效的光捕获器的观察结果。最后，我们发现结合到 CP29 复合物 L2 位点的紫黄质与相邻的叶绿素结合非常紧密。
