HL-LH2中色素分子间的单重激发态能量传递

采用飞秒时间分辨吸收光谱手段观测了在500和800 nm激发下高光培养的紫色光合细菌Rhodopseu-domonas(Rps). palustris外周捕光天线LH2(HL-LH2)中不同共轭链长类胡萝卜素(Carotenoid, 简称Car)和细菌叶绿素a(Bacteriachlorophyll a, 简称BChl a)的特征吸收光谱. 光谱动力学分析结果表明, HL-LH2中不同Car分子间可能存在复杂的单重激发态能量平衡过程, Car分子同时向BChl a分子发生多途径的单重激发态能量传递, B800主要接受来自Car的S2和S1态能量; B850则主要接受来自长共轭链Car(共轭双键数目n=13)的S1态和B800的激发态能量, 整个能量传递过程在3~5 ps内完成.

Singlet Excited State Energy Transfer Among Pigments in HL-LH2

Under excitation of 500 and 800 nm, femto-second time-resolved absorption spectroscopy was used to observe the characteristic absorption of carotenoids(Cars) with various conjugation lengths and bacteriochlorophyll a(BChl a) with different Qy bands, i.e. B800 and B850 aggregates, in the high light cultured peri-pheral light-harvesting complex(HL-LH2) from Rhodopseudomonas(Rps.) palustris. Spectroscopic dynamics analysis suggests that the complicated singlet excited state energy equilibrium possibly exists among various carotenoids and multi-channel singlet excited state energy transfer occurs between Cars and BChl as. B800 mainly accepts the excitation energy from S1 and S2 states of Cars, and B850 from the S1 state of Car with the longest conjugation length(conjugated double bonds number n=13) and B800 as well. The whole singlet excited state energy transfer process can be completed in 3—5 ps.