Hayashi H, Noguchi T, Tasumi M, Atkinson G H
Department of Chemistry, University of Arizona, Tucson 85721.
Biophys J. 1991 Jul;60(1):252-60. doi: 10.1016/S0006-3495(91)82047-1.
The vibrational spectroscopy and population dynamics of excited singlet (2(1)Ag), excited triplet (3B u), and the ground (1Ag) electronic states of carotenoids in chromatophores of Chromatium vinosum (mainly spirilloxanthin and rhodopin) and of the same carotenoids in benzene solutions are examined by picosecond time-resolved resonance Raman scattering. Coherent Stokes Raman scattering from the ground states of carotenoids in chromatophores also is observed. Resonance Raman spectra of in vitro rhodopin and spirilloxanthin when compared with in vivo data demonstrate that scattering from spirilloxanthin dominates the in vivo spectrum. Comparisons of the time-dependent intensities of 2(1)Ag and 1Ag resonance Raman bands from both in vitro and in vivo carotenoids suggest that vibrationally excited levels in 1Ag are populated directly by the decay of the 2(1)Ag state and that these levels relax into a thermalized distribution in less than 50 ps. The appearance of asymmetrically broadened, ground-state resonance Raman bands supports this conclusion. Formation of the 3Bu state is observed for carotenoids in chromatophores, but not for in vitro spirilloxanthin indicating that the 3Bu state is formed by fission processes originating from the spatial organization of pigments within chromatophores. The rate at which the intensities of 2(1)Ag resonance Raman bands decay is faster for the carotenoids in vivo than for those in vitro thereby indicating that additional relaxation channels (e.g., energy transfer to bacteriochlorophylls) are present in the chromatophore. The similarity of the in vivo and in vitro 2(1)Ag resonance Raman spectra shows that no significant modifications in the vibronic coupling has been caused by the chromatophore environment.
利用皮秒时间分辨共振拉曼散射，研究了嗜硫红假单胞菌（主要是螺旋藻黄素和玫红菌红素）色素小体中类胡萝卜素的激发单重态（2(1)Ag）、激发三重态（3B u）以及基态（1Ag）的振动光谱和布居动力学，以及相同类胡萝卜素在苯溶液中的情况。还观察到了色素小体中类胡萝卜素基态的相干斯托克斯拉曼散射。体外玫红菌红素和螺旋藻黄素的共振拉曼光谱与体内数据相比表明，螺旋藻黄素的散射在体内光谱中占主导。对体外和体内类胡萝卜素的2(1)Ag和1Ag共振拉曼带随时间变化的强度比较表明，1Ag中的振动激发能级直接由2(1)Ag态的衰变填充，并且这些能级在不到50皮秒的时间内弛豫到热平衡分布。不对称展宽的基态共振拉曼带的出现支持了这一结论。在色素小体中观察到类胡萝卜素形成3Bu态，但体外螺旋藻黄素未观察到，这表明3Bu态是由色素小体中色素的空间组织引发的裂变过程形成的。体内类胡萝卜素的2(1)Ag共振拉曼带强度衰减速率比体外的快，这表明色素小体中存在额外的弛豫通道（例如，向细菌叶绿素的能量转移）。体内和体外2(1)Ag共振拉曼光谱的相似性表明，色素小体环境未对振动电子耦合造成显著改变。
