【摘要】 光系统Ⅱ反应中心包含有 2个去镁叶绿素分子 (Pheo) ,2个 β胡萝卜素分子 (β Car)和 6个叶绿素a分子 (Chla) 对反应中心的时间分辨荧光光谱表明 ,两个β Car具有不同的吸收光谱 ,吸收峰分别为 4 89nm(Car4 89)和 5 0 7nm(Car5 0 7) ,Car4 89靠近吸收峰为 6 6 7nm和 6 75nm的叶绿素a(Chla) ,它的主要功能是保护反应中心免受单态氧的破坏 ,而不能将激发能传递给光化学反应活性的色素分子P6 80 ;Car5 0 7靠近吸收峰为 6 6 9nm的Chla分子 ;能够将激发能传递给P6 80 ,进行电荷分离 采用全局优化拟合的方法对荧光光谱进行处理 ,Car4 89在 6 1ps时间内将能量传递给Chla6 72 ,随后传给Chla6 77,处于激发态的Chla6 77在 3ns衰减到基态 ;Car5 0 7在 2 74ps时间内将能量传递给P6 80 ,P6 80 + Pheo- 的电荷重组发生在 3.8ns和 16ns更多还原

【Abstract】 Fluorescence spectroscopy was used to learn the characteristics of pigments of photosystem Ⅱ. The purified photosystem Ⅱ (PS Ⅱ) reaction center contains approximately six molecules of chlorophyll a (Chl a), two β-carotene (β-Car) and two pheophytin a (Pheo a). The fluorescence spectra demonstrated that the reaction center has two different spectral form β-Car molecules designated as Car489 and Car507. Car489 is located close to Chl a form with peaks at 672 nm and 677 nm (Chl a672, Chl a 677) on protein D2. The function of Car489 is to protect reaction center from photodamage. Car507 is located close to Chl a forms with 672 nm (Chl a672) on protein D1 and can transfer energy to Chl a672 and/or other pigments, then to P680 to generate charge separation. A global analysis-fitting program was used to fit the fluorescence spectra. The results showed that Car489 transfers energy to Chl a672, then to Chl a677 in 61 ps, the excited state of Chl a677 decay to the ground state in 3 ns,on protein D2. Car507 transfers energy to P680 via some pigments in 274 ps,on protein D1. The recombinations of primary pair P680+Pheo a- take place in 3.8 ns and 16 ns.更多还原