Noguchi T, Inoue Y
Solar Energy Research Group, Institute of Physical and Chemical Research (RIKEN), Saitama.
J Biochem. 1995 Jul;118(1):9-12. doi: 10.1093/oxfordjournals.jbchem.a124897.
Fourier transfer infrared (FTIR) signals originating from a high-potential electron acceptor in PS II were studied by flash-induced FTIR difference spectroscopy. Redox titration of these signals using ferri-ferrocyanide mixtures showed midpoint potentials (Em) of 489 +/- 12 and 426 +/- 9 mV at pH 5.5 and 6.5, respectively, revealing a pH dependence of about -60 mV/pH unit. These Em values and pH dependence were in good agreement with those of the non-heme iron, so-called Q400, located between QA and QB. This indicates that the observed FTIR signals are due to changes in ligands of the non-heme iron and surrounding protein moieties induced on photoreduction from Fe3+ to Fe2+.
通过闪光诱导傅里叶变换红外（FTIR）差示光谱法研究了源自光系统II中高电位电子受体的FTIR信号。使用铁氰化铁 - 亚铁氰化铁混合物对这些信号进行氧化还原滴定，结果表明，在pH 5.5和6.5时，中点电位（Em）分别为489±12和426±9 mV，显示出约-60 mV/pH单位的pH依赖性。这些Em值和pH依赖性与位于QA和QB之间的非血红素铁（即所谓的Q400）的Em值和pH依赖性高度一致。这表明观察到的FTIR信号是由于光还原过程中从Fe3+到Fe2+引起的非血红素铁及其周围蛋白质部分的配体变化所致。
