Annunziata Onofrio, Paduano Luigi, Pearlstein Arne J, Miller Donald G, Albright John G
Department of Chemistry, Texas Christian University, Fort Worth, Texas 76129, USA.
J Phys Chem B. 2006 Jan 26;110(3):1405-15. doi: 10.1021/jp054543c.
We use accurate thermodynamic derivatives extracted from high-precision measurements of the four volume-fixed diffusion coefficients in ternary solutions of lysozyme chloride in aqueous NaCl, NH4Cl, and KCl at pH 4.5 and 25 degrees C to (a) assess the relative contributions of the common-ion and nonideality effects to the protein chemical potential as a function of salt concentration, (b) compare the behavior of the protein chemical potential for the three salts, which we found to be consistent with the Hofmeister series, and (c) discuss our thermodynamic data in relation to the dependence of the protein solubility on salt concentration. The four diffusion coefficients are reported at 0.6 mM lysozyme chloride and 0.25, 0.5, 0.9, 1.2, and 1.5 M KCl and extend into the protein-supersaturated region. The chemical potential cross-derivatives are extracted from diffusion data using the Onsager reciprocal relation and the equality of molal cross-derivatives of solute chemical potentials. They are compared to those calculated previously from diffusion data for lysozyme in aqueous NaCl and NH4Cl. We estimate the effective charge on the diffusing lysozyme cation at the experimental concentrations. Our diffusion measurements on the three salts allowed us to analyze and interpret the four diffusion coefficients for charged proteins in the presence of 1:1 electrolytes. Our results may provide guidance to the understanding of protein crystallization.
我们使用从高精度测量中提取的精确热力学导数，这些测量针对的是在pH 4.5和25摄氏度下，溶菌酶氯化物在NaCl、NH4Cl和KCl水溶液的三元溶液中的四个体积固定扩散系数，以（a）评估共离子和非理想效应作为盐浓度函数对蛋白质化学势的相对贡献，（b）比较三种盐的蛋白质化学势行为，我们发现其与霍夫迈斯特序列一致，以及（c）讨论我们的热力学数据与蛋白质溶解度对盐浓度的依赖性之间的关系。四个扩散系数是在0.6 mM溶菌酶氯化物以及0.25、0.5、0.9、1.2和1.5 M KCl条件下报告的，并且延伸到蛋白质过饱和区域。化学势交叉导数是使用昂萨格互易关系和溶质化学势的摩尔交叉导数相等性从扩散数据中提取的。将它们与先前从溶菌酶在NaCl和NH4Cl水溶液中的扩散数据计算得到的结果进行比较。我们估计了实验浓度下扩散的溶菌酶阳离子的有效电荷。我们对三种盐的扩散测量使我们能够分析和解释在1:1电解质存在下带电蛋白质的四个扩散系数。我们的结果可能为理解蛋白质结晶提供指导。
