Ion effects on macromolecules in aqueous solution
Ion effects on macromolecules in aqueous solution
复制标题
水溶液中离子对大分子的影响
作者：
M. J. Hey;J. Clough;D. Taylor
除了它们的非特异性静电相互作用外，离子还可以对水溶液中大分子的构象和溶解度产生特异性影响1。阴离子和阳离子在改变大分子构型方面的相对有效性与大分子的性质无关，通常被称为溶性或霍夫迈斯特系列。为了解释这种效应的普遍性，经常援引离子对溶剂结构的影响，但迄今为止还没有理论能够令人满意地将离子-水相互作用与离子对大分子的影响联系起来。我们认为这是离子对溶剂空体积的影响，这是霍夫迈斯特级数的基础，我们推导了一个简单的热力学方程，它解释了盐对聚合物链聚集过程转变温度的影响。为了验证这个方程，我们从文献中获取了与聚乙烯醇（PVME；分子间聚集）的云点有关的数据；和核糖核酸酶的热转变温度（分子内聚集）。
APART from their nonspecific electrostatic interactions, ions can produce specific effects on the conformation and solubility of macromolecules in aqueous solution1. The relative effectiveness of anions and cations in altering macromolecular configurations is remarkably independent of the nature of the macromolecule and is generally referred to as the lyotropic or Hofmeister series. To explain the generality of the effects, the influence of the ions on the structure of the solvent has often been invoked, but as yet no theory has been able to link satisfactorily ion–water interactions with the effects of ions on macromolecules. We argue here that it is the effect of the ions on the empty volume of the solvent which underlies the Hofmeister series and we derive a simple thermodynamic equation which accounts for the effect of a salt on the transition temperature for a polymer chain aggregation process. To test the equation we have taken data from the literature relating to the cloud point of polyvinylmethylether (PVME; intermolecular aggregation); and to the thermal transition temperature of ribonuclease (intramolecular aggregation).