Fedorov Maxim V, Goodman Jonathan M, Schumm Stephan
Max Planck Institute for Mathematics in the Sciences, Inselstrasse 22, D04103 Leipzig, Germany.
J Am Chem Soc. 2009 Aug 12;131(31):10854-6. doi: 10.1021/ja9030374.
Molecular dynamics simulations demonstrate that differences in the interaction of sodium and potassium with the carboxylate side chains of alpha-poly-L-glutamate (alpha-PGA) have a dramatic effect on the conformational properties of the polypeptide. Potassium ions cluster mainly in the second and third solvation shells of alpha-PGA because their low charge density makes the electrostatic interactions between them and alpha-PGA too weak for K(+) to compete with water for the first solvation shell of the alpha-PGA glutamic acid residuals. Unlike sodium ions, they do not switch the conformation of alpha-PGA from extended to alpha-helical. Potentials of mean force for pure water, sodium ion solutions, and potassium ion solutions show marked differences in ion association behavior. This supports the idea that Hofmeister effects depend upon direct ion-macromolecule interactions as well as interactions with water molecules in the first solvation shell rather than bulk water structuring.
分子动力学模拟表明，钠和钾与α-聚-L-谷氨酸（α-PGA）羧酸盐侧链相互作用的差异对多肽的构象性质有显著影响。钾离子主要聚集在α-PGA的第二和第三溶剂化层中，因为它们的低电荷密度使得它们与α-PGA之间的静电相互作用太弱，以至于K(+)无法与水竞争α-PGA谷氨酸残基的第一溶剂化层。与钠离子不同，它们不会使α-PGA的构象从伸展型转变为α-螺旋型。纯水、钠离子溶液和钾离子溶液的平均力势在离子缔合行为上表现出显著差异。这支持了霍夫迈斯特效应取决于直接的离子-大分子相互作用以及与第一溶剂化层中水分子的相互作用，而不是取决于本体水结构的观点。
