Amino acid side chain interactions in the presence of salts
Amino acid side chain interactions in the presence of salts
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DOI：
10.1021/jp054042r
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发表时间：
2005-11-24
影响因子：
3.3
通讯作者：
Hassan, SA
中科院分区：
文献类型：
--
作者：
Hassan, SA
通过分子动力学模拟研究了盐对极性/带电氨基酸分子间相互作用的影响。计算了NaCl在298 K下0 ~ 2 M浓度范围内的平均力和相关电位。研究发现，盐的加入可以稳定或破坏相互作用，这取决于相互作用分子的性质。（去）稳定的程度是量化的，并在分析溶剂密度分布的基础上讨论了盐依赖性调制的来源。为了深入了解盐调制的分子起源，计算了空间分布函数（sdf），揭示了所有情况下高度的溶剂结构性。sdf的峰与连接溶质亲水基团的远程氢键网络相一致，这有助于它们的分子间溶剂诱导力。分析了溶质紧密接触解离时，溶质周围水的结构变化。这一分析为溶剂结构如何调节复杂溶质中有效的分子间相互作用提供了线索。这种调节是由体积静电力和(i)单体之间的结构区域中的水分子施加的静电力之间的临界平衡造成的，这些静电力被短暂进入水化壳层的离子破坏，以及（ii）水化壳层中的离子与溶质直接相互作用。简要讨论了这些发现在蛋白质/配体（非共价）结合/解离机制中的意义。
The effects of salt on the intermolecular interactions between polar/charged amino acids are investigated through molecular dynamics simulations. The mean forces and associated potentials are calculated for NaCl salt in the 0-2 M concentration range at 298 K. It is found that the addition of salt may stabilize or destabilize the interactions, depending on the nature of the interacting molecules. The degree of (de)stabilization is quantified, and the origin of the salt-dependent modulation is discussed based upon an analysis of solvent density profiles. To gain insight into the molecular origin of the salt modulation, spatial distribution functions (sdf's) are calculated, revealing a high degree of solvent structuredness in all cases. The peaks in the sdf's are consistent with long-range hydrogen-bonding networks connecting the solute hydrophilic groups, and that contribute to their intermolecular solvent-induced forces. The restructuring of water around the solutes as they dissociate from close contact is analyzed. This analysis offers clues on how the solvent structure modulates the effective intermolecular interactions in complex solutes. This modulation results from a critical balance between bulk electrostatic forces and those exerted by (i) the water molecules in the structured region between the monomers, which is disrupted by ions that transiently enter the hydration shells, and (ii) the ions in the hydration shells in direct interactions with the solutes. The implications of these findings in protein/ligand (noncovalent) association/dissociation mechanisms are briefly discussed.