Microscopic redox equilibrium constants and standard redox potential values were determined to quantify selenolate-diselenide equilibria of biological significance. The highly composite, codependent acid-base and redox equilibria of selenolates could so far be converted into pH-dependent, apparent parameters (equilibrium constants, redox potentials) only. In this work, the selenolate-diselenide redox equilibria of selenocysteamine and selenocysteine against dithiothreitol were analyzed by quantitative nuclear magnetic resonance (NMR) methods to characterize the interfering acid-base and redox equilibria. The directly obtained, pH-dependent, conditional redox equilibrium constants were then decomposed by our method into pH-independent, microscopic constants, which characterize the two-electron redox transitions of selenocysteamine and selenocysteine. The 12 different, species-specific parameter values show close correlation with the respective selenolate basicities, providing a tool to estimate otherwise inaccessible site-specific selenolate-diselenide redox potentials of related moieties in large peptides and proteins.

中文翻译：

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硒代半胱氨酸和硒代半胱胺的物种特异性，pH无关标准氧化还原电势。

确定微观氧化还原平衡常数和标准氧化还原电势值，以量化具有生物学意义的硒酸酯-二硒化物平衡。硒酸盐的高度复合的，相互依赖的酸碱和氧化还原平衡到目前为止只能转化为pH依赖的表观参数（平衡常数，氧化还原电势）。在这项工作中，通过定量核磁共振（NMR）方法分析了硒代半胱胺和硒代半胱氨酸的硒酸酯-二硒化物氧化还原平衡，以表征干扰酸碱和氧化还原平衡。然后，通过我们的方法将直接获得的，pH依赖性的条件氧化还原平衡常数分解为pH无关的微观常数，其特征在于硒代半胱胺和硒代半胱氨酸的两个电子的氧化还原转变。12种不同的物种特异性参数值与各自的硒酸酯基础性密切相关，从而提供了一种工具来估计大分子肽段和蛋白质中相关部分的位点特异性硒酸酯-二硒化物氧化还原电位。