ZINC-COMPLEXES OF CYSTEINE, HISTIDINE, AND DERIVATIVES THEREOF - POTENTIOMETRIC DETERMINATION OF THEIR COMPOSITIONS AND STABILITIES
ZINC-COMPLEXES OF CYSTEINE, HISTIDINE, AND DERIVATIVES THEREOF - POTENTIOMETRIC DETERMINATION OF THEIR COMPOSITIONS AND STABILITIES
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DOI：
10.1002/hlca.19930760133
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发表时间：
1993-01-01
影响因子：
1.8
通讯作者：
ZUBERBUHLER, AD
中科院分区：
文献类型：
--
作者：
GOCKEL, P;VAHRENKAMP, H;ZUBERBUHLER, AD
测定了半胱氨酸和组氨酸的锌配合物的稳定性，以及它们的三个给体功能（分别为羧基、氨基和巯基和咪唑）被阻断的三个衍生物的稳定性。使用水溶液电位滴定法，在存在的各种物质中观察到所有四种半胱氨酸和所有四种组氨酸衍生配体的1:1和1:2配合物（配体，1:1和1:2配合物及其质子化衍生物）。所有半胱氨酸衍生的复合物都比相应的组氨酸衍生复合物稳定，在1:1组合物中稳定1-2个数量级，在1:2组合物中稳定1-6个数量级。对于半胱氨酸系列，稳定性顺序为半胱氨酸b>半胱氨酸乙酯远大于N(α)-乙酰半胱氨酸远大于s -甲基半胱氨酸。组氨酸系列对应的序列为组氨酸>组氨酸甲酯> NN（咪唑）-二甲基组氨酸> N(α)-乙酰组氨酸。稳定性的顺序可以用Zn-S与Zn-N配位的相对强度、电荷效应和螯合物的大小来解释。
The stabilities of Zn complexes of cysteine and histidine have been determined together with those of three derivatives of each in which one of their three donor functions (carboxyl, amino, and mercapto and imidazole respectively) has been blocked. Using potentiometric titrations of aqueous solutions, the 1:1 and 1:2 complexes of all four cysteine- and all four histidine-derived ligands are observed among the various species present (ligands, 1:1 and 1:2 complexes, and protonated derivatives thereof). All cysteine-derived complexes are more stable than the corresponding histidine-derived complexes by 1-2 orders of magnitude for the 1:1 composition and by 1-6 orders of magnitude for the 1:2 composition. For the cysteine series, the sequence of stabilities is cysteine > cysteine ethyl ester much greater than N(alpha)-acetylcysteine much greater than S-methylcysteine. For the histidine series, the corresponding sequence is histidine > histidine methyl ester > NN(imidazole)-dimethylhistidine > N(alpha)-acetylhistidine. The order of stabilities can be explained by the relative strengths of the Zn-S vs. Zn-N coordination, by charge effects, and by chelate nn sizes.