Owens T G, Webb S P, Alberte R S, Mets L, Fleming G R
Department of Molecular Genetics and Cell Biology, University of Chicago, Illinois 60637.
Biophys J. 1988 May;53(5):733-45. doi: 10.1016/S0006-3495(88)83154-0.
The temporal and spectral properties of fluorescence decay in isolated photosystem I (PS I) preparations from algae and higher plants were measured using time-correlated single photon counting. Excitations in the PS I core antenna decay with lifetimes of 15-40 ps and 5-6 ns. The fast decay results from efficient photochemical quenching by P700, whereas the slow decay is attributed to core antenna complexes lacking a trap. Samples containing core and peripheral antenna complexes exhibited an additional intermediate lifetime (150-350 ps) decay. The PS I core antenna is composed of several spectral forms of chlorophyll a that are not temporally resolved in the decays. Analysis of the temporal and spectral properties of the decays provides a description of the composition, structure, and dynamics of energy transfer and trapping reactions in PS I. The core antenna size dependence of the spectral properties and the contributions of the spectral forms to the time-resolved decays show that energy is not concentrated in the longest wavelength absorbing pigments but is nearly homogenized among the spectral forms. These data suggest that the "funnel" description of antenna structure and energy transfer (Seely, G. R. 1973. J. Theor. Biol. 40:189-199) may not be applicable to the PS I core antenna.
利用时间相关单光子计数法测量了来自藻类和高等植物的分离光系统I（PS I）制剂中荧光衰减的时间和光谱特性。PS I核心天线中的激发以15 - 40皮秒和5 - 6纳秒的寿命衰减。快速衰减源于P700的有效光化学猝灭，而缓慢衰减则归因于缺乏陷阱的核心天线复合体。含有核心和外周天线复合体的样品表现出额外的中间寿命（150 - 350皮秒）衰减。PS I核心天线由几种叶绿素a的光谱形式组成，这些形式在衰减过程中在时间上无法分辨。对衰减的时间和光谱特性的分析提供了对PS I中能量转移和俘获反应的组成、结构和动力学的描述。光谱特性对核心天线大小的依赖性以及光谱形式对时间分辨衰减的贡献表明，能量并非集中在吸收最长波长的色素中，而是在光谱形式之间几乎均匀分布。这些数据表明，天线结构和能量转移的“漏斗”描述（Seely，G. R. 1973. J. Theor. Biol. 40:189 - 199）可能不适用于PS I核心天线。
