Bao Han, Zhang Chunxi, Ren Yanan, Zhao Jingquan
Laboratory of Photochemistry, Beijing National Laboratory of Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
Biochim Biophys Acta. 2010 Mar;1797(3):339-46. doi: 10.1016/j.bbabio.2009.12.001. Epub 2010 Jan 6.
The correlation between the reduction of Q(A) and the oxidation of Tyr(Z) or Car/Chl(Z)/Cyt(b559) in spinach PSII enriched membranes induced by visible light at 10 K is studied by using electron paramagnetic resonance spectroscopy. Similar g=1.95-1.86 Q(A)(-)EPR signals are observed in both Mn-depleted and intact samples, and both signals are long lived at low temperatures. The presence of PPBQ significantly diminished the light induced EPR signals from Q(A)(-), Car(+)/Chl(+) and oxidized Cyt(b559), while enhancing the amplitude of the S(1)Tyr(Z)* EPR signal in the intact PSII sample. The quantification and stability of the g=1.95-1.86 EPR signal and signals arising from the oxidized Tyr(Z) and the side-path electron donors, respectively, indicate that the EPR-detectable g=1.95-1.86 Q(A)(-) signal is only correlated to reaction centers undergoing oxidation of the side-path electron donors (Car/Chl(Z)/Cyt(b559)), but not of Tyr(Z). These results imply that two types of Q(A)(-) probably exist in the intact PSII sample. The structural difference and possible function of the two types of Q(A) are discussed.
利用电子顺磁共振光谱研究了10K可见光诱导菠菜富含光系统II的膜中Q(A)的还原与Tyr(Z)或Car/Chl(Z)/Cyt(b559)氧化之间的相关性。在贫锰样品和完整样品中均观察到类似g=1.95-1.86的Q(A)(-)EPR信号，且这两种信号在低温下寿命都很长。PPBQ的存在显著减弱了来自Q(A)(-)、Car(+)/Chl(+)和氧化态Cyt(b559)的光诱导EPR信号，同时增强了完整光系统II样品中S(1)Tyr(Z)* EPR信号的幅度。g=1.95-1.86的EPR信号以及分别来自氧化态Tyr(Z)和旁路电子供体的信号的定量和稳定性表明，EPR可检测到的g=1.95-1.86 Q(A)(-)信号仅与经历旁路电子供体（Car/Chl(Z)/Cyt(b559)）氧化的反应中心相关，而与Tyr(Z)的氧化无关。这些结果表明完整光系统II样品中可能存在两种类型的Q(A)(-)。讨论了这两种类型Q(A)的结构差异和可能的功能。
