Rabenstein D L, Greenberg M S, Evans C A
Biochemistry. 1977 Mar 8;16(5):977-81. doi: 10.1021/bi00624a026.
Proton magnetic resonance studies of the acid-base chemistry of the glycyl ammonium, histidyl imidazolium, and lysyl ammonium groups of glycyl-L-histidyl-L-lysine and of the glycyl ammonium and histidyl imidazolium groups of glycyl-L-histidine and glycyl-L-histidylglycine are described. Chemical-shift data indicate that, at the molecular level, the glycyl ammonium and the histidyl imidazolium groups are titrated over the same pH range, with the acidity of the imidazolium group some 8 to 10 times that of the glycyl ammonium group, depending on the peptide. The lysyl ammonium group of Gly-His-Lys is much less acidic and is titrated over a higher pH range. Microscopic and macroscopic acid-dissociation constants were determined from chemical-shift data for each of the peptides. It is shown how microscopic formation constants for protonated metal complexes of these ligands, which are being used increasingly as models for the binding of metal ions by proteins, can be calculated from the macroscopic formation constants and the microscopic acid-dissociation constants. The acid-base chemistry of Gly-His-Lys is discussed with respect to its recently discovered biological activity.
描述了对甘氨酰-L-组氨酰-L-赖氨酸的甘氨酰铵基、组氨酰咪唑鎓基和赖氨酰铵基，以及甘氨酰-L-组氨酸和甘氨酰-L-组氨酰甘氨酸的甘氨酰铵基和组氨酰咪唑鎓基进行的酸碱化学的质子磁共振研究。化学位移数据表明，在分子水平上，甘氨酰铵基和组氨酰咪唑鎓基在相同的pH范围内被滴定，咪唑鎓基的酸度比甘氨酰铵基约高8至10倍，这取决于肽。甘氨酰-组氨酰-赖氨酸的赖氨酰铵基酸性要弱得多，且在更高的pH范围内被滴定。根据每种肽的化学位移数据确定了微观和宏观酸解离常数。展示了如何根据宏观形成常数和微观酸解离常数计算这些配体的质子化金属配合物的微观形成常数，这些配体越来越多地被用作蛋白质结合金属离子的模型。针对甘氨酰-组氨酰-赖氨酸最近发现的生物活性，讨论了其酸碱化学。
