THE ASSOCIATION OF IMIDAZOLE WITH THE IONS OF ZINC AND CUPRIC COPPER
THE ASSOCIATION OF IMIDAZOLE WITH THE IONS OF ZINC AND CUPRIC COPPER
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DOI：
10.1021/ja01640a068
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发表时间：
1954-01-01
影响因子：
15
通讯作者：
GURD, FRN
中科院分区：
文献类型：
--
作者：
EDSALL, JT;FELSENFELD, G;GURD, FRN
咪唑与锌离子和铜离子的相互作用通过对含有咪唑、咪唑鎓离子以及铜或锌离子的溶液以及离子强度为0.16的硝酸根离子的溶液中的pH测量来确定。在这两种情况下，发现咪唑离子的配位数为4。Cu++的连续对数内在缔合常数为4.5：4.00、3.63、3.27和2.90；对于 Zn++：2.16、2.32、2.53 和 2.80。还确定了 22.5 或 24 的缔合常数，并对缔合过程中的焓和标准熵变化进行了近似估计。描述了乔治·斯卡查德教授开发的一种快速评估数据关联常数的新方法。铜-咪唑配合物在 590 至 690 µ 之间的可见光和 230 至 290 mji 之间的紫外线中显示出显着的吸收。铜和氨基之间的复合物不显示后一种类型的吸收。铜-组氨酸络合物的吸收光谱表明组氨酸的咪唑残基参与了形成的螯合键。咪唑基团由于其存在于组胺和组氨酸中而在生物化学中发挥着重要作用。组氨酸的咪唑基团实际上通常负责生理pYi范围内蛋白质的大部分缓冲能力。关于组氨酸的咪唑基团与金属离子的结合已有一些工作报道，并已获得证据5·1 23
The interaction of imidazole with the ions of zinc and cupric copper was determined by means of pH measurements on solutions containing imidazole, imidazolium ion and either copper or zinc ions, in solutions containing nitrate ion at ionic strength 0.16. In both cases it was found that the coordination number of the ion for imidazole was 4. The successive logarithmic intrinsic associationconstants at 4.5 were for Cu++: 4.00, 3.63, 3.27 and 2.90; and for Zn++: 2.16, 2.32, 2.53 and 2.80. Association constants at 22.5 or 24 were also determined, and approximate estimates of enthalpy and standard entropy changes in the association processes have been made. A new and rapid method for evaluating the associa-tion constants from the data, developed by ProfessorGeorge Scatchard, is described. Copper-imidazole complexesshow marked absorption in the visible between590 and 690 µ and in the ultraviolet between230 and 290 mji. The latter type of absorption is not shown by complexes between copper and amino groups. Absorption spectra of the copper-histidine complex indicate that the imidazole residues of histidine are involved in the chelate linkages formed.The imidazole group plays an important role in biochemistry because of its presence in histamine and histidine. The imidazole groups ofhistidine are indeed generally responsible for most of the buffering power of proteins in the physiological pYi range. Some work has been reported on the binding of metallic ions by the imidazole groups of histidine, and evidence has been obtained5· 1 23