Ono T A, Inoue Y
Solar Energy Research Group, Institute of Physical and Chemical Research, Saitama, Japan.
Arch Biochem Biophys. 1988 Jul;264(1):82-92. doi: 10.1016/0003-9861(88)90573-5.
The inhibitory effects of NH3 on S-state turnovers were studied by curve fitting and deconvolution of thermoluminescence glow curves and low-temperature EPR spectroscopy. The following results were found: (i) High concentrations of NH3 upshifted the recombination temperatures of both S2QB- and S2QA- charge pairs, indicating formation of an abnormal S2 state having a lowered oxidation potential. (ii) The abnormal S2 was correlated to alterations in EPR multiline signal: high concentrations of NH3 induced the modified multiline signal having reduced hyperfine line spacing, accompanied by disappearance of the g = 4.1 signal, while low concentrations of NH3 reduced the line width of the g = 4.1 signal with a slight shift in its g value to 4.2 concomitant with suppression in amplitude of the normal multiline signal, both suggesting coordination of NH3 to the Mn center. (iii) More than half of the NH3-binding abnormal S2 centers underwent S-state turnover to yield S3QB- and S3QA- pairs having normal thermoluminever, the NH3-binding S3 was unable to undergo further S-state turnovers. (iv) The interruption of S-state turnover at S3 was assumed to be due to the inability of electron abstraction from the S3 state. Based on these, the mechanism of NH3 inhibition was discussed.
通过对热释光发光曲线进行曲线拟合和反卷积以及低温电子顺磁共振光谱研究了NH₃对S态周转的抑制作用。发现以下结果：(i) 高浓度的NH₃使S₂QB⁻和S₂QA⁻电荷对的复合温度升高，表明形成了氧化电位降低的异常S₂态。(ii) 异常S₂与电子顺磁共振多线信号的变化相关：高浓度的NH₃诱导了超精细线间距减小的修饰多线信号，同时g = 4.1信号消失，而低浓度的NH₃降低了g = 4.1信号的线宽，其g值轻微移至4.2，同时正常多线信号的幅度受到抑制，两者均表明NH₃与Mn中心配位。(iii) 超过一半的与NH₃结合的异常S₂中心经历S态周转，产生具有正常热释光的S₃QB⁻和S₃QA⁻对，与NH₃结合的S₃无法进行进一步的S态周转。(iv) 假定S₃处S态周转的中断是由于无法从S₃态提取电子。基于这些，讨论了NH₃抑制的机制。
