Faculty of Physics, Adam Mickiewicz University, ul. Uniwersytetu Poznanskiego 2, 61-614 Poznań, Poland.
Department of Optometry, Poznan University of Medical Sciences, ul. Rokietnicka 5d, 60-806 Poznań, Poland.
J Phys Chem B. 2021 Aug 12;125(31):8742-8756. doi: 10.1021/acs.jpcb.1c03978. Epub 2021 Jul 30.
Light-induced electron-transfer reactions were investigated in wild-type and three mutant reaction centers with the secondary electron acceptor (ubiquinone Q) either removed or permanently reduced. Under such conditions, charge separation between the primary electron donor (bacteriochlorophyll dimer, P) and the electron acceptor (bacteriopheophytin, H) was followed by PH → PH charge recombination. Two reaction centers were used that had different single amino-acid mutations that brought about either a 3-fold acceleration in charge recombination compared to that in the wild-type protein, or a 3-fold deceleration. In a third mutant in which the two single amino-acid mutations were combined, charge recombination was similar to that in the wild type. In all cases, data from transient absorption measurements were analyzed using similar models. The modeling included the energetic relaxation of the charge-separated states caused by protein dynamics and evidenced the appearance of an intermediate charge-separated state, PB, with B being the bacteriochlorophyll located between P and H. In all cases, mixing of the states PB and PH was observed and explained in terms of electron delocalization over B and H. This delocalization, together with picosecond protein relaxation, underlies a new view of primary charge separation in photosynthesis.
光诱导电子转移反应在野生型和三个突变体反应中心中进行,其中二级电子受体(泛醌 Q)被去除或永久还原。在这种情况下,初级电子供体(细菌叶绿素二聚体,P)和电子受体(细菌叶啉,H)之间的电荷分离随后是 PH→PH 电荷复合。使用了两个反应中心,它们具有不同的单个氨基酸突变,与野生型蛋白相比,电荷复合的速度加快了 3 倍,或者减慢了 3 倍。在第三个突变体中,两个单氨基酸突变结合在一起,电荷复合与野生型相似。在所有情况下,瞬态吸收测量的数据都使用类似的模型进行分析。该模型包括由蛋白质动力学引起的电荷分离态的能量弛豫,并证明了中间电荷分离态 PB 的出现,其中 B 是位于 P 和 H 之间的细菌叶绿素。在所有情况下,都观察到了 PB 和 PH 态的混合,并根据 B 和 H 上的电子离域来解释这种混合。这种离域,以及皮秒级的蛋白质弛豫,构成了光合作用中初级电荷分离的新观点。