Excluded volume in solvation: sensitivity of scaled-particle theory to solvent size and density.
Excluded volume in solvation: sensitivity of scaled-particle theory to solvent size and density.
复制标题
溶剂化中的排除体积：缩放粒子理论对溶剂尺寸和密度的敏感性。
DOI：
10.1016/s0006-3495(00)76470-8
复制
发表时间：
2000
影响因子：
3.4
通讯作者：
Bloomfield,VA
中科院分区：
文献类型：
--
作者：
Tang,KE;Bloomfield,VA
溶剂环境的变化极大地影响大分子结构和稳定性。为了研究排除体积在溶剂化中的作用，通常使用比例粒子理论来计算 ΔGtrev，即溶质转移自由能 ΔGtr 的排除体积部分。 SPT 的输入是溶剂半径和摩尔浓度。真正的分子不是球体。因此，分子半径并不是唯一定义的，并且对于任何给定物种来说都是不同的。由于 ΔGtrevis 对溶剂半径极其敏感，因此这些半径的不确定性导致 ΔGtrev 存在很大的不确定性 - 对于氨基酸溶质从水转移到水性混合物的数 kcal/mol。这种不确定性大于实验的 ΔGtr 值。此外，ΔGtrev 可以是正值，也可以是负值。添加中性拥挤分子不一定会降低溶解度。最后，ΔGtrevis 对溶剂密度 ρ 非常敏感。 ρ 中的几个百分点的误差甚至可能导致 ΔGtrev 的定性偏差。例如，如果通过假设硬球压力恒定来计算 ρ，则 ΔGtrev 值和不确定性现在仅为十分之一 kcal/mol 并且为正值。由于按比例粒子理论计算的 ΔGtrev 值对溶剂半径和密度非常敏感，因此使用 SPT 确定排除体积对转移自由能的贡献可能会存在问题。
Changes in solvent environment greatly affect macromolecular structure and stability. To investigate the role of excluded volume in solvation, scaled-particle theory is often used to calculate ΔGtrev, the excluded-volume portion of the solute transfer free energy, ΔGtr. The inputs to SPT are the solvent radii and molarities. Real molecules are not spheres. Hence, molecular radii are not uniquely defined and vary for any given species. Since ΔGtrevis extremely sensitive to solvent radii, uncertainty in these radii causes a large uncertainty in ΔGtrev—several kcal/mol for amino acid solutes transferring from water to aqueous mixtures. This uncertainty is larger than the experimental ΔGtrvalues. Also, ΔGtrevcan be either positive or negative. Adding neutral crowding molecules may not necessarily reduce solubility. Lastly, ΔGtrevis very sensitive to solvent density,ρ. A few percent error inρmay even cause qualitative deviations in ΔGtrev. For example, ifρis calculated by assuming the hard-sphere pressure to be constant, then ΔGtrevvalues and uncertainties are now only tenths of a kcal/mol and are positive. Because ΔGtrevvalues calculated by scaled-particle theory are strongly sensitive to solvent radii and densities, determining the excluded-volume contribution to transfer free energies using SPT may be problematic.