Cherepanov Dmitry A, Semenov Alexey Yu, Mamedov Mahir D, Aybush Arseniy V, Gostev Fedor E, Shelaev Ivan V, Shuvalov Vladimir A, Nadtochenko Victor A
N.N. Semenov Federal Research Center for Chemical Physics, Russian Academy of Sciences, 119991, Kosygina Street 1, Moscow, Russia.
A.N. Belozersky Institute of Physical-Chemical Biology, M.V. Lomonosov Moscow State University, 119992 Leninskye gory 1 building, 40 Moscow, Russia.
Biophys Rev. 2022 Aug 15;14(4):805-820. doi: 10.1007/s12551-022-00983-1. eCollection 2022 Aug.
This review analyzes new data on the mechanism of ultrafast reactions of primary charge separation in photosystem I (PS I) of cyanobacteria obtained in the last decade by methods of femtosecond absorption spectroscopy. Cyanobacterial PS I from many species harbours 96 chlorophyll (Chl ) molecules, including six specialized Chls denoted Chl/Chl (dimer P, or PP), Chl/Chl, and Chl/Chl arranged in two branches, which participate in electron transfer reactions. The current data indicate that the primary charge separation occurs in a symmetric exciplex, where the special pair P is electronically coupled to the symmetrically located monomers Chl and Chl, which can be considered together as a symmetric exciplex ChlPPChl with the mixed excited (ChlPPChl) and two charge-transfer states P Chl and P Chl . The redistribution of electrons between the branches in favor of the -branch occurs after reduction of the Chl and Chl monomers. The formation of charge-transfer states and the symmetry breaking mechanisms were clarified by measuring the electrochromic Stark shift of β-carotene and the absorption dynamics of PS I complexes with the genetically altered or monomers. The review gives a brief description of the main methods for analyzing data obtained using femtosecond absorption spectroscopy. The energy levels of excited and charge-transfer intermediates arising in the cyanobacterial PS I are critically analyzed.
本综述分析了近十年来通过飞秒吸收光谱法获得的关于蓝藻光系统I（PS I）中初级电荷分离超快反应机制的新数据。许多物种的蓝藻PS I含有96个叶绿素（Chl）分子，包括六个特殊的叶绿素，分别表示为Chl/Chl（二聚体P，或PP）、Chl/Chl和Chl/Chl，它们排列在两个分支中，参与电子转移反应。目前的数据表明，初级电荷分离发生在一个对称的激基复合物中，其中特殊对P与对称定位的单体Chl和Chl发生电子耦合，它们可以一起被视为一个对称激基复合物ChlPPChl，具有混合激发态（ChlPPChl）和两个电荷转移态P Chl 和P Chl 。在Chl和Chl单体还原后，电子在分支之间重新分配，有利于 - 分支。通过测量β-胡萝卜素的电致变色斯塔克位移以及具有基因改变的 或 单体的PS I复合物的吸收动力学，阐明了电荷转移态的形成和对称性破缺机制。本综述简要描述了分析使用飞秒吸收光谱法获得的数据的主要方法。对蓝藻PS I中产生的激发态和电荷转移中间体的能级进行了批判性分析。
