光系统Ⅱ反应中心D1—D2—Cyt b-559的分离纯化及其性质研究

ISOLATION AND CHARACTERIZATION OF PHOTOSYSTEM II REACTION CENTER D1-D2-CYTOCHROME b-559 COMPLEX FROM THE CHLOROPLASTS OF SPINACH

采用柱层析法从菠菜叶绿体中分离纯化得到高等植物光系统Ⅱ(PSII)反应中心色素蛋白复合体 D_1-D_2-Cyt b-559,并对其性质进行了研究。该反应中心中所含的色素比大约为Ch1a/2 Pheo a=6.0。四阶导数光谱在红区有两个峰,说明该反应中心至少存在两种结合状态的 Chl a。相位调制法得到的时间分辩荧光光谱的研究结果表明,该三元复合物的荧光至少是3指数衰减,其寿命分别为:1.51ns、6.23nS、36.26nS,占整个荧光的分数依次为:0.06,0.67,0.27。其中寿命为6.23nS 的荧光为与电荷分离不相关的 Ch1 a 所产生;寿命为1.51ns 的组分所占比例很小,其来源不清楚;寿命为36.25nS 的组分为原初电子供体 P680与原初电子受体 Pheo a 发生电荷重组时产生的荧光,这个组分的荧光直接反映了该反应中心的电荷分离活性。

photosystem ll reaction center D_1一D_2-cytochrome b一559 pigment-protein compIex has been isolated and purified from chloroplasts of spinaoh and its properties have been studied. The ,so- tated photosystem.lI reaction center contains close to six chlorophyll a per two pheophytin a mo- lecules. Analysis of fluorescence decaying by phase modulation fluorometry suggests that the reaction center has three components of fluorescence decaying with lifetimes of 1.5 nS, 6.23 ns, 36.26 nS in terms of fractions to total fluorescence yield as 0.06, 0.67, 0.27 respectively. The 5.25 nS fluorescence component corresp.onds to chlorophyll a which is energetically uncoupled from the process of charge separation. The proportion of 1.51 nS component is very low, and its source is unclear. The 36.25 nS fluorescence component is attributed tO the recombination of the primary radical pair, and so represents the activity of charge separation.