Temperature-dependent pulsed electron paramagnetic resonance studies of the S2 state multiline signal of the photosynthetic oxygen-evolving complex.
Temperature-dependent pulsed electron paramagnetic resonance studies of the S2 state multiline signal of the photosynthetic oxygen-evolving complex.
复制标题
光合放氧复合物 S2 态多线信号的温度依赖性脉冲电子顺磁共振研究。
DOI：
10.1021/bi00206a009
复制
发表时间：
1994
期刊：
影响因子：
2.9
通讯作者：
Britt,RD
中科院分区：
文献类型：
--
作者：
Lorigan,GA;Britt,RD
摘要：在4.2-11 K的温度范围内，通过反转恢复脉冲EPR技术，直接测量了处于5）态的光系统II放氧复合物的g= 2“多线”锰电子顺磁共振（EPR）信号的电子自旋-晶格弛豫速率（1/7）。g= 2“多线”信号的电子自旋回波幅度在此范围内与温度成反比，表明基态自旋态居里定律行为与我们先前报道的工作一致[布里特等人，（1992）Biochim. Biophys. Acta 1140，95-101]，电子自旋-晶格弛豫速率的自然对数与温度倒数的关系曲线的结果与作为该温度范围内“多线”信号的主要弛豫途径的Orbach机制一致。图的斜率表明，激发自旋态流形存在36.5 cm-1以上的基态流形，产生的“多线”signal.Higher植物光合作用进化O2通过一个循环的水氧化过程中发生的光系统II（PSII）的放氧复合体（OEC）1。该循环（Kok等人，1970），涉及五个状态，S 0-S4，其中下标表示OEC的净氧化态。状态S1-S4通过光生P680+阳离子对OEC的顺序单电子氧化产生。酪氨酸残基Yz在每个转变中充当电子转移中间体（巴里和Babcock，1987; Debus等人，1988年）。在S4状态产生后，分子氧从OEC自发释放，并且OEC重置为So状态，因为它被来自两个氧化的底物水分子的四个电子再还原。循环的最终结果是释放一个氧分子，并将四个电子转移到PSII的醌电子受体分子上。OEC的详细结构尚未确定，但电子顺磁共振（EPR）研究已经证明OEC含有四核Mn簇（Kim等人，
Revised Manuscript Received August 1, 1994® abstract: The electron spin-lattice relaxation rate (1/7)) of the g= 2 “multiline” manganese electron paramagnetic resonance(EPR) signal arisingfrom the photosystem II oxygen-evolving complex poised in the 5) state has been directly measured over the temperature range of 4.2-11 K via the inversion-recovery pulsed EPR technique. The electron spin echo amplitude of the g= 2 “multiline” signal varies inversely with temperature over this range, indicating a ground spin state Curie law behavior in agreement with our previously reported work [Britt et al.(1992) Biochim. Biophys. Acta 1140, 95-101], Results of a plot of the natural log of the electron spin-lattice relaxation rate versus reciprocal temperature are consistent with an Orbach mechanism serving as the dominant relaxation pathway for the “multiline” signal in this temperature range. The slope of the plot indicates that an excited spin state manifold exists 36.5 cm-1 above the groundstate manifold that gives rise to the “multiline” signal.Higher plant photosynthesis evolves O2 through a cyclic water oxidation process occurring in the oxygen-evolving complex (OEC) 1 of photosystem II (PSII). This cycle (Kok et al., 1970), involves five states, S0-S4, where the subscript represents the net oxidized state of the OEC. States S1-S4 are produced by sequential single-electron oxidations of the OEC by the photogenerated P68o+ cation. The tyrosine residue Yz serves as an electron transfer intermediate in each transition (Barry & Babcock, 1987; Debus et al., 1988). Molecular oxygen is spontaneously released from the OEC after the S4 state is generated, and the OEC resets to the So state as it is rereduced by four electrons from the two oxidized substrate water molecules. The net result of the cycle is the release of an oxygen molecule and the transfer of the four electrons to the quinone electron acceptor molecules of PSII. The detailed structure of the OEC has not been determined, but electron paramagnetic resonance(EPR) studies have demonstrated that the OEC contains a tetranuclear Mn cluster (Kim et al.,