Appleton D W, Sarkar B
Bioinorg Chem. 1977;7(3):211-24. doi: 10.1016/s0006-3061(00)80095-2.
Mixed aquo-N-methylimidazole complexes of Co(II) have been studied as a function of pH to gain a fuller understanding of the metal-binding site in Co(II)-carbonic anhydrase. The inherent affinity of N-methylimidazole for Co(II) has been calculated along with a species distribution for the stepwise addition of ligand to the metal ion. From these studies, it is apparent that the occurrence of Zn(II) rather than Co(II) in native carbonic anhydrase can be explained by the stronger affinity of Zn(II) for imidazole and the preference of Zn(II) for a tetrahedral geometry as offered by the enzyme. Octahedral Co(II) fails to ionize metal bound water. However, at high pH, Co(II)-N-methylimidazole complexes interact directly with the hydroxide ion, generating species with visible spectra very similar to that of Co(II)-carbonic anhydrase. Tentative structures have been proposed for these species.
已对钴（II）的混合水合-N-甲基咪唑配合物进行了研究，该研究将其作为pH的函数，以更全面地了解钴（II）-碳酸酐酶中的金属结合位点。已计算出N-甲基咪唑对钴（II）的固有亲和力以及配体逐步添加到金属离子时的物种分布。从这些研究中可以明显看出，天然碳酸酐酶中锌（II）而非钴（II）的存在可以通过锌（II）对咪唑的更强亲和力以及锌（II）对酶提供的四面体几何结构的偏好来解释。八面体钴（II）不会使与金属结合的水离子化。然而，在高pH值下，钴（II）-N-甲基咪唑配合物直接与氢氧根离子相互作用，生成具有与钴（II）-碳酸酐酶非常相似的可见光谱的物种。已为这些物种提出了初步结构。
