Redox thermodynamics of the Fe3+/Fe2+ couple in horseradish peroxidase and its cyanide complex
Redox thermodynamics of the Fe3+/Fe2+ couple in horseradish peroxidase and its cyanide complex
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DOI：
10.1021/ja017188m
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发表时间：
2002-01-09
影响因子：
15
通讯作者：
Sola, M
中科院分区：
文献类型：
--
作者：
Battistuzzi, G;Borsari, M;Sola, M
通过变温紫外-维斯光谱电化学实验，确定了辣根过氧化物酶的五配位高自旋天然形式及其六配位低自旋氰化物加合物的Fe 3+还原为Fe 2+的热力学。在这两种情况下，ΔH ° 'rc和ΔS °' rc值均为正值。因此，负的还原势是两个相反的和部分补偿的贡献的结果：一个大的熵项，这是两个物种的负E °'值的决定因素，和一个较小的，但相关的熵贡献。Fe ~（3+）/Fe ~（2+）电对与氰化物结合时E °'的降低是一种完全熵效应，明确地表明了熵效应在决定氧化还原金属中心E °'值中的重要性。
The thermodynamics of Fe3+to Fe2+reduction for the five-coordinate high-spin native form of horseradish peroxidase and for its six-coordinate low-spin cyanide adduct have been determined from variable-temperature UV−vis spectroelectrochemical experiments. In both cases, the ΔH°‘rcand ΔS°‘rcvalues are positive. Hence, the negative reduction potentials turn out to be the result of two opposing and partially compensating contributions: a large enthalpic term, which is the determinant of the negativeE°‘ values for both species, and a smaller, yet relevant, entropic contribution. The decrease inE°‘ of the Fe3+/Fe2+couple on cyanide binding turns out to be a fully entropic effect, unequivocally demonstrating the importance of entropic effects in determining theE°‘ values of redox metal centers.