Department of Applied Chemistry, The University of Tokyo, Bunkyo-ku, Tokyo, Japan; Research Center for Advanced Science and Technology, The University of Tokyo, Meguro-ku, Tokyo, Japan.
Department of Applied Chemistry, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.
Biophys J. 2023 Feb 7;122(3):470-483. doi: 10.1016/j.bpj.2023.01.002. Epub 2023 Jan 5.
We evaluated excitation energy transfer (EET) coupling (J) between all pairs of chlorophylls (Chls) and pheophytins (Pheos) in the protein environment of photosystem II based on the time-dependent density functional theory with a quantum mechanical/molecular mechanics approach. In the reaction center, the EET coupling between Chls P and P is weaker (|J(P/P)| = 79 cm), irrespective of a short edge-to-edge distance of 3.6 Å (Mg-to-Mg distance of 8.1 Å), than the couplings between P and the accessory Chl (|J(P/Chl)| = 104 cm) and between P and Chl (|J(P/Chl)| = 101 cm), suggesting that P and P are two monomeric Chls rather than a "special pair". There exist strongly coupled Chl pairs (|J| > ∼100 cm) in the CP47 and CP43 core antennas, which may be candidates for the red-shifted Chls observed in spectroscopic studies. In CP47 and CP43, Chls ligated to CP47-His26 and CP43-His56, which are located in the middle layer of the thylakoid membrane, play a role in the "hub" that mediates the EET from the lumenal to stromal layers. In the stromal layer, Chls ligated to CP47-His466, CP43-His441, and CP43-His444 mediate the EET from CP47 to Chl/Pheo and from CP43 to Chl/Pheo in the reaction center. Thus, the excitation energy from both CP47 and CP43 can always be utilized for the charge-separation reaction in the reaction center.
我们基于含时密度泛函理论与量子力学/分子力学相结合的方法，评估了光合作用系统 II 中蛋白质环境下所有叶绿素（Chl）和原叶绿素（Pheo）之间的激发能量转移（EET）耦合（J）。在反应中心，叶绿素 P 与 P 之间的 EET 耦合较弱（|J（P/P）|=79 cm），尽管它们之间的边缘到边缘距离较短（3.6 Å）（Mg 到 Mg 距离为 8.1 Å），但弱于 P 与辅助 Chl 之间的耦合（|J（P/Chl）|=104 cm）和 P 与 Chl 之间的耦合（|J（P/Chl）|=101 cm），这表明 P 和 P 是两个单体叶绿素，而不是“特殊对”。CP47 和 CP43 核心天线中存在强耦合的叶绿素对（|J|>∼100 cm），它们可能是光谱研究中观察到的红移叶绿素的候选者。在 CP47 和 CP43 中，与 CP47-His26 和 CP43-His56 配位的叶绿素位于类囊体膜的中层，在从中层到基质层的 EET 过程中起着“枢纽”的作用。在基质层中，与 CP47-His466、CP43-His441 和 CP43-His444 配位的叶绿素介导 CP47 到 Chl/Pheo 和 CP43 到 Chl/Pheo 的 EET，从而使 CP47 和 CP43 的激发能量都能用于反应中心的电荷分离反应。
