Yamauchi T, Mino H, Matsukawa T, Kawamori A, Ono T
Faculty of Science, Kwansei Gakuin University, Nishinomiya, Japan.
Biochemistry. 1997 Jun 17;36(24):7520-6. doi: 10.1021/bi962791g.
Magnetic properties of the S1-state manganese cluster in the oxygen-evolving photosystem II were studied by parallel polarization electron paramagnetic resonance spectroscopy. Dark minus light spectra gave rise to a broad S1-state signal with a g value of about 4.9 [Dexheimer, S. L., Klein, M. P. (1992) J. Am. Chem. Soc. 114, 2821-2826]. Temperature variation of the signal intensity between 1.9 and 10 K observed in PS II with a sucrose buffer indicates that the signal originates from an excited state with a spin S of 1 with separation from the ground state (S = 0) of about 2.5 K. The S1-state signal was also observed in the sucrose buffer supplemented by 50% glycerol. However, no S1-state signal was detected by addition of 3% methanol or 30% ethylene glycol in the sucrose buffer, although illumination at 200 K in the presence of these alcohols induced the normal multiline S2 signal. Furthermore, modification of the Mn cluster by Cl- or Ca2+ depletion from PS II membranes failed to produce a detectable S1-state signal. A possible magnetic structure of the Mn cluster responsible for the generation of the S1-state signal is discussed on the basis of these observations.
通过平行极化电子顺磁共振光谱研究了放氧光系统II中S1态锰簇的磁性。暗态减去光态光谱产生了一个g值约为4.9的宽S1态信号[德克斯海默，S. L.，克莱因，M. P.（1992年）《美国化学会志》114，2821 - 2826]。在含有蔗糖缓冲液的光系统II中观察到，信号强度在1.9至10 K之间随温度变化，这表明该信号源自自旋S为1的激发态，与基态（S = 0）的能量间隔约为2.5 K。在添加了50%甘油的蔗糖缓冲液中也观察到了S1态信号。然而，在蔗糖缓冲液中添加3%甲醇或30%乙二醇后未检测到S1态信号，尽管在这些醇存在下于200 K光照会诱导出正常的多线S2信号。此外，通过从光系统II膜中去除Cl-或Ca2+来修饰锰簇，未能产生可检测到的S1态信号。基于这些观察结果，讨论了负责产生S1态信号的锰簇可能的磁性结构。
