Salt Effects on Hydrophobic Solvation: Is the Observed Salt Specificity the Result of Excluded Volume Effects or Water Mediated Ion-Hydrophobe Association?,ChemPhysChem

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Salt Effects on Hydrophobic Solvation: Is the Observed Salt Specificity the Result of Excluded Volume Effects or Water Mediated Ion-Hydrophobe Association?
ChemPhysChem ( IF 2.3 ) Pub Date : 2020-01-31 , DOI: 10.1002/cphc.201901000
Olga A Francisco ₁ , Hayden M Glor ₁ , Mazdak Khajehpour _{1,

2}

Affiliation

The solubility of hydrophobic molecules in water is sensitive to salt addition in an ion‐specific manner. Such “salting‐out” and “salting‐in” properties have been shown to be a major contributor to the measured ion‐specific Hofmeister effects that are observed in many biophysical phenomena. Various theoretical models have suggested a number of disparate mechanisms for salting‐out (salting‐in) of hydrophobic moieties, the most popular of which include preferential interaction, water‐mediated association, and electrostriction models. However, a complete molecular level description of this ion‐specificity is not yet available. This work investigates the ion‐specific nature of hydrophobic solvation by studying how sodium and chloride salts affect the thermodynamics of 1,2‐hexanediol micellization. The results of this study are analyzed in terms of scaled‐particle theory and we show that salt addition can affect hydrophobic solvation in two modalities: salt addition changes the cavitation free energy; salt addition also influences the solvent‐solute interaction energy by changing the hydration of the hydrophobic solute. These two effects are salt specific in nature and we suggest that for small hydrophobic solutes these effects are the main cause of salt‐specific Hofmeister effects on their solubility.

中文翻译：

盐对疏水溶剂化的影响：观察到的盐特异性是排除体积效应还是水介导的离子-疏水菌缔合的结果？

疏水分子在水中的溶解度对离子加成盐敏感。这种“盐析”和“盐析”特性已被证明是在许多生物物理现象中观察到的离子特异性霍夫迈斯特效应的主要贡献者。各种理论模型都提出了许多不同的疏水性部分盐析（盐析）的机制，其中最受欢迎的机制包括优先相互作用，水介导的缔合和电致伸缩模型。但是，尚无关于此离子特异性的完整分子水平描述。这项工作通过研究钠盐和氯化物盐如何影响1,2-己二醇胶束化的热力学来研究疏水溶剂化的离子特异性。本研究的结果是按比例尺理论进行分析的，我们表明盐的添加可以两种方式影响疏水溶剂化：盐添加改变了空化自由能；盐的添加还通过改变疏水性溶质的水合作用而影响溶剂-溶质的相互作用能。这两种作用本质上是盐特异性的，我们建议对于小的疏水性溶质，这些作用是盐特异性霍夫迈斯特作用对其溶解度的主要原因。

更新日期：2020-01-31

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