ABNORMAL SOLUBILITY BEHAVIOR OF BETA-LACTOGLOBULIN - SALTING-IN BY GLYCINE AND NACL
ABNORMAL SOLUBILITY BEHAVIOR OF BETA-LACTOGLOBULIN - SALTING-IN BY GLYCINE AND NACL
复制标题
DOI：
10.1021/bi00390a038
复制
发表时间：
1987-08-11
期刊：
影响因子：
2.9
通讯作者：
TIMASHEFF, SN
中科院分区：
文献类型：
--
作者：
ARAKAWA, T;TIMASHEFF, SN
β-γ-Al_2O_3盐溶的原因通过详细研究这些溶剂组分与蛋白质之间的相互作用，探索了甘氨酸和NaCl对乳球蛋白的溶解度行为，这与预期相反。β-β的优先相互作用在甘氨酸和NaCl水溶液体系中，乳球蛋白与溶剂组分的反应与牛血清白蛋白和溶菌酶的反应进行了比较。在中性pH下，β-乳球蛋白在低共溶剂浓度下在甘氨酸和NaCl中表现出不显著的优先相互作用，并且在较高浓度下表现出增加的优先水合作用，该水平接近从其他两种蛋白质预期的值。这些结果表明电解质与β-葡萄糖的相当大的结合。乳球蛋白，足以补偿由于溶剂表面张力的扰动引起的排斥。β-β的优先相互作用之间的差异乳球蛋白和其它蛋白质与这两种溶剂添加剂的混合显示是β-即使在高浓度的添加剂下，乳球蛋白的溶解度也很高，在高浓度下，它们对其他蛋白质具有盐析作用。检查NaCl与这三种蛋白质的优先相互作用作为pH的函数。结果表明，对于牛血清白蛋白和溶菌酶，优先水合没有pH依赖性，而对于β-溶菌酶，该参数显著增加。这表明电解质与β-乳球蛋白的结合在较低的pH下是不稳定的。乳球蛋白的这种差异是由于在中性pH附近蛋白质表面上的独特电荷分布，这赋予该蛋白质大的偶极矩。
The causes of the salting-in of .beta.-lactoglobulin by glycine and NaCl, a solubility behavior contrary to expectations, were probed by a detailed study of the interactions between these solvent components and the protein. The preferential interactions of .beta.-lactoglobulin with solvent components in aqueous glycine and NaCl systems have been compared with those of bovine serum albumin and lysozyme. At neutral pH, .beta.-lactoglobulin exhibited insignificant preferential interactions in glycine and NaCl at low cosolvent concentrations and an increasing preferential hydration at higher concentrations, the levels approaching the values expected from the other two proteins. These results indicate considerable binding of the electrolytes to .beta.-lactoglobulin, sufficient to compensate for the exclusion due to perturbation of the solvent surface tension. The difference between the preferential interactions of .beta.-lactoglobulin and the other proteins with these two solvent additives was shown to be the cause of the increase of .beta.-lactoglobulin solubility even at high concentrations of the additives, at which they have salting-out effects on the other proteins. The preferential interactions of NaCl with the three proteins were examined as a function of pH. The results showed no pH dependence of the preferential hydration for bovine serum albumin and lysozyme, while this parameter increased significantly for .beta.-lactoglobulin at lower pH. This suggests that the binding of electrolytes to .beta.-lactoglobulin is due to a unique charge distribution on the surface of the protein around neutral pH, which imparts to this protein a large dipole moment.