Primary charge separation within P870* in wild type and heterodimer mutants in femtosecond time domain

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• 作者：R.A. Khatypov ; A.Yu. Khmelnitskiy ; A.M. Khristin ; T.Yu. Fufina ; L.G. Vasilieva ; V.A. Shuvalov ; ^{shuvalov@issp.serpukhov.su}
• 关键词：RC ; reaction center ; Rba ; Rhodobacter ; ET ; electron transfer ; BChl ; bacteriochlorophyll ; P870 ; Bacteriochlorophyll dimer ; PA ; PB ; primary electron donor bacteriochlorophyll molecules belonging to the A and B symmetric cofactor branches ; BPheo ; bacteriophe
• 刊名：Biochimica et Biophysica Acta (BBA)/Bioenergetics
• 出版年：2012
• 期刊代码：13_00052728
• 类别：bio
• 出版时间：August, 2012
• 卷：1817
• 期：8
• 页码：1392-1398
• 文件大小：1032 K

摘要

Primary charge separation dynamics in the reaction center (RC) of purple bacterium Rhodobacter sphaeroides and its P870 heterodimer mutants have been studied using femtosecond time-resolved spectroscopy with 20 and 40 fs excitation at 870 nm at 293 K. Absorbance increase in the 1060-1130 nm region that is presumably attributed to P_A^未+ cation radical molecule as a part of mixed state with a charge transfer character P*(P_A^未+P_B^{未鈭?/sup>) was found. This state appears at 120-180 fs time delay in the wild type RC and even faster in H(L173)L and H(M202)L heterodimer mutants and precedes electron transfer (ET) to B_A bacteriochlorophyll with absorption band at 1020 nm in WT. The formation of the P_A未+B_A未鈭?/sup> state is a result of the electron transfer from P*(P_A未+P_B未鈭?/sup>) to the primary electron acceptor B_A (still mixed with P*) with the apparent time delay of ~ 1.1 ps. Next step of ET is accompanied by the 3-ps appearance of bacteriopheophytin a鈭?/sup> (H_A鈭?/sup>) band at 960 nm. The study of the wave packet formation upon 20-fs illumination has shown that the vibration energy of the wave packet promotes reversible overcoming of an energy barrier between two potential energy surfaces P* and P*(P_A未+B_A未鈭?/sup>) at ~ 500 fs. For longer excitation pulses (40 fs) this promotion is absent and tunneling through an energy barrier takes about 3 ps. This article is part of a Special Issue entitled: Photosynthesis Research for Sustainability: from Natural to Artificial.}