A. N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Leninskie Gory, 119992 Moscow, Russia.
J Phys Chem B. 2012 Mar 8;116(9):2886-90. doi: 10.1021/jp2033214. Epub 2012 Feb 22.
The mechanism of two-photon excitation of a peripheral light-harvesting complex LH2 (B800-850) from purple bacterium Rhodobacter sphaeroides was explained on the basis of femtosecond transient absorption data. Fast bleaching of the B850 absorption band was measured under two-photon excitation by 1350 nm femtosecond pulses, showing fast subpicosecond arrival of excitation energy to B850 circular aggregates. Any spectral changes connected with the B800 absorption band of B800-BChl molecules were absent. A similar picture was observed under one-photon excitation of the LH2 complex by 675 nm femtosecond pulses. We believe these effects may be attributed to direct excitation of high-energy excitonic states of a B850 circular aggregate or its vibrational manifold in accordance with the model of Abe [Chem. Phys. 2001, 264, 355-363].
基于飞秒瞬态吸收数据，解释了从紫色细菌球形红杆菌的外周光捕获复合物 LH2（B800-850）进行双光子激发的机制。通过 1350nm 飞秒脉冲的双光子激发测量了 B850 吸收带的快速漂白，表明激发能量快速亚皮秒到达 B850 圆聚集体。与 B800-BChl 分子的 B800 吸收带相关的任何光谱变化都不存在。在通过 675nm 飞秒脉冲对 LH2 复合物进行的单光子激发下也观察到了类似的情况。我们相信这些效应可能归因于 B850 圆聚集体的高能激子态或其振动模态的直接激发，符合 Abe 的模型[Chem. Phys. 2001, 264, 355-363]。
