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10K下细菌反应中心激发态的飞秒光谱演化

Femtosecond spectral evolution of the excited state of bacterial reaction centers at 10 K.

作者信息

Vos M H, Lambry J C, Robles S J, Youvan D C, Breton J, Martin J L

机构信息

Laboratoire d'Optique Appliquée, Institut National de la Santé et de la Recherche Médicale Unité 275, Ecole Polytechnique-Ecole Nationale Supérieure de Techniques Avancées, Palaiseau, France.

出版信息

Proc Natl Acad Sci U S A. 1992 Jan 15;89(2):613-7. doi: 10.1073/pnas.89.2.613.

Abstract

The femtosecond spectral evolution of reaction centers of Rhodobacter sphaeroides R-26 was studied at 10 K. Transient spectra in the near infrared region, obtained with 45-fs pulses (pump pulses centered at 870 nm and continuum probe pulses), were analyzed with associated kinetics at specific wavelengths. The t = 0-fs transient spectrum is very rich in structure; it contains separate induced bands at 807 and 796 nm and a bleaching near 760 nm, reflecting strong changes in interaction between all pigments upon formation of the excited state. A complex spectral evolution in the 800-nm region, most notably the bleaching of the 796-nm band, takes place within a few hundred femtosecond--i.e., on a time scale much faster than electron transfer from the primary donor P to the bacteriopheophytin acceptor HL. The remarkable initial spectral features and their evolution are presumably related to the presence of HL, as they were not observed in the DLL mutant of Rhodobacter capsulatus, which lacks this pigment. A simple linear reaction scheme with an intermediate state cannot account for our data; the initial spectral evolution must reflect relaxation processes within the excited state. The importance for primary photochemistry of long distance interactions in the reaction center is discussed.

摘要

在10K温度下研究了球形红细菌R-26反应中心的飞秒光谱演化。利用45飞秒脉冲(泵浦脉冲中心波长为870nm,连续探测脉冲)获得近红外区域的瞬态光谱,并结合特定波长下的动力学进行分析。t = 0飞秒时的瞬态光谱结构非常丰富;它在807和796nm处包含单独的诱导带,在760nm附近有一个漂白带,这反映了激发态形成时所有色素之间相互作用的强烈变化。800nm区域内发生了复杂的光谱演化,最显著的是796nm带的漂白,这发生在几百飞秒内——即时间尺度比从初级供体P到细菌叶绿素受体HL的电子转移要快得多。这些显著的初始光谱特征及其演化可能与HL的存在有关,因为在缺乏这种色素的荚膜红细菌DLL突变体中未观察到这些特征。一个具有中间态的简单线性反应方案无法解释我们的数据;初始光谱演化必须反映激发态内的弛豫过程。讨论了反应中心中长距离相互作用对初级光化学的重要性。

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