Solubility of lysozyme in the presence of aqueous chloride salts: Common-ion effect and its role on solubility and crystal thermodynamics
Solubility of lysozyme in the presence of aqueous chloride salts: Common-ion effect and its role on solubility and crystal thermodynamics
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DOI：
10.1021/ja804304e
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发表时间：
2008-10-08
影响因子：
15
通讯作者：
Wang, Ying
中科院分区：
文献类型：
--
作者：
Annunziata, Onofrio;Payne, Andrew;Wang, Ying
了解蛋白质的溶解性对于合理设计蛋白质结晶条件是非常重要的。我们报告测量溶菌酶在水溶液中的溶解度作为NaCl，KCl和NH4Cl浓度的函数，在25 ℃和pH 4.5。我们的溶解度的结果直接比较，这些三元溶液中确定在相同的实验条件下三元扩散的优先相互作用系数。这一比较为蛋白质溶解度对盐浓度的依赖性提供了新的重要见解。我们注意到，作为盐浓度的函数的偏好相互作用系数的依赖性基本上是由共离子效应形成的。这种效应对观察到的溶菌酶溶解度行为也起着至关重要的作用。我们发现，盐的类型和浓度的溶解度的依赖性强烈相关的优先相互作用系数的相应的依赖性。优先相互作用系数和第二维里系数的检查，使我们能够证明，盐浓度的溶解度依赖性的实质上是由相应的蛋白质化学势的变化在结晶相的影响。我们提出了一个简单的模型的结晶相的基础上盐溶液和水合蛋白质晶体之间的分配。一种新的溶解度方程的报告，定量地解释了所观察到的实验依赖性的蛋白质溶解度盐浓度。
Understanding protein solubility is important for a rational design of the conditions of protein crystallization. We report measurements of lysozyme solubility in aqueous solutions as a function of NaCl, KCl, and NH4Cl concentrations at 25 degrees C and pH 4.5. Our solubility results are directly compared to preferential-interaction coefficients of these ternary solutions determined in the same experimental conditions by ternary diffusion. This comparison has provided new important insight on the dependence of protein solubility on salt concentration. We remark that the dependence of the preferential-interaction coefficient as a function of salt concentration is substantially shaped by the common-ion effect. This effect plays a crucial role also on the observed behavior of lysozyme solubility. We find that the dependence of solubility on salt type and concentration strongly correlates with the corresponding dependence of the preferential-interaction coefficient. Examination of both preferential-interaction coefficients and second virial coefficients has allowed us to demonstrate that the solubility dependence on salt concentration is substantially affected by the corresponding change of protein chemical potential in the crystalline phase. We propose a simple model for the crystalline phase based on salt partitioning between solution and the hydrated protein crystal. A novel solubility equation is reported that quantitatively explains the observed experimental dependence of protein solubility on salt concentration.