Electrochromic band-shifts have been investigated in Photosystem II (PSII) from Thermosynechoccocus elongatus. Firstly, by using Mn-depleted PsbA1-PSII and PsbA3-PSII in which the QX absorption of PheD1 differs, a band-shift in the QX region of PheD2 centered at ~ 544 nm has been identified upon the oxidation, at pH 8.6, of TyrD. In contrast, a band-shift due to the formation of either QA•- or TyrZ• is observed in PsbA3-PSII at ~ 546 nm, as expected with E130 H-bonded to PheD1 and at ~ 544 nm as expected with Q130 H-bonded to PheD1. Secondly, electrochromic band-shifts in the Chla Soret region have been measured in O2-evolving PSII in PsbA3-PSII, in the PsbA3/H198Q mutant in which the Soret band of PD1 is blue shifted and in the PsbA3/T179H mutant. Upon TyrZ•QA•- formation the Soret band of PD1 is red shifted and the Soret band of ChlD1 is blue shifted. In contrast, only PD1 undergoes a detectable S-state dependent electrochromism. Thirdly, the time resolved S-state dependent electrochromism attributed to PD1 is biphasic for all the S-state transitions except for S1 to S2, and shows that: i) the proton release in S0 to S1 occurs after the electron transfer and ii) the proton release and the electron transfer kinetics in S2 to S3, in T. elongatus, are significantly faster than often considered. The nature of S2TyrZ• is discussed in view of the models in the literature involving intermediate states in the S2 to S3 transition.

中文翻译：

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我们仍然可以从Photosystem II中的电致变色带移中学到什么？

已经在来自嗜热嗜热球菌的光系统II（PSII）中研究了电致变色带移。首先，通过使用贫锰的PsbA1-PSII和PsbA3-PSII（其中PheD1的QX吸收不同），在pH 8.6的条件下氧化PheD2的QX区域中，在〜544 nm处出现了带移。 TyrD。相反，在PsbA3-PSII中观察到由于QA•-或TyrZ•形成的带移，如E130 H键合到PheD1所预期的那样，在〜544 nm处，如Q130 H-预期的那样，在〜544 nm处观察到了。绑定到PheD1。其次，已经在PsbA3-PSII中，O2演变的PSII，PsbA3 / H198Q突变体（其中PD1的Soret带发生了蓝移）和PsbA3 / T179H突变体中，测定了Chla Soret区的电致变色带移。在TyrZ•QA•-形成后，PD1的Soret带发生红移，而ChlD1的Soret带发生蓝移。相反，仅PD1经历了可检测的S态依赖性电致变色。第三，归因于PD1的时间分辨的S态依赖电致变色对于除S1到S2之外的所有S态跃迁都是双相的，这表明：i）S0到S1中的质子释放发生在电子转移之后; ii）在质子虫中，质子释放和S2到S3的电子转移动力学比通常认为的要快得多。根据文献中涉及S2到S3过渡中的中间状态的模型，讨论了S2TyrZ•的性质。归因于PD1的时间分辨的S态依赖电致变色对于除S1到S2之外的所有S态跃迁都是双相的，这表明：i）S0到S1中的质子释放发生在电子转移之后； ii）质子释放并且在T.longateus中S2到S3的电子转移动力学比通常考虑的要快得多。根据文献中涉及S2到S3过渡中的中间状态的模型，讨论了S2TyrZ•的性质。归因于PD1的时间分辨的S态依赖电致变色对于除S1到S2之外的所有S态跃迁都是双相的，这表明：i）S0到S1中的质子释放发生在电子转移之后； ii）质子释放并且在T.longateus中S2到S3的电子转移动力学比通常考虑的要快得多。根据文献中涉及S2到S3过渡中的中间状态的模型，讨论了S2TyrZ•的性质。