Pertsemlidis A, Soper A K, Sorenson J M, Head-Gordon T
Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA.
Proc Natl Acad Sci U S A. 1999 Jan 19;96(2):481-6. doi: 10.1073/pnas.96.2.481.
We have combined neutron solution scattering experiments with molecular dynamics simulation to isolate an excess experimental signal that is caused solely by N-acetyl-leucine-amide (NALA) correlations in aqueous solution. This excess signal contains information about how NALA molecule centers are correlated in water, and we show how these solute-solute correlations might be determined at dilute concentrations in the small angle region. We have tested qualitatively different pair distribution functions for NALA molecule centers-gas, cluster, and aqueous forms of gc(r)-and have found that the excess experimental signal is adequate enough to rule out gas and cluster pair distribution functions. The aqueous form of gc(r) that exhibits a solvent-separated minimum, and possibly longer-ranged correlations as well, is not only physically sound but reproduces the experimental data reasonably well. This work demonstrates that important information in the small angle region can be mined to resolve solute-solute correlations, their lengthscales, and thermodynamic consequences even at dilute concentrations. The hydration forces that operate on the microscopic scale of individual amino acid side chains, implied by the small angle scattering data, could have significant effects on the early stages of protein folding, on ligand binding, and on other intermolecular interactions.
我们将中子溶液散射实验与分子动力学模拟相结合，以分离出仅由水溶液中N - 乙酰 - 亮氨酸 - 酰胺（NALA）的相关性引起的过量实验信号。这个过量信号包含了NALA分子中心在水中如何相关的信息，并且我们展示了在小角度区域的稀浓度下如何确定这些溶质 - 溶质相关性。我们已经对NALA分子中心的气体、簇和水合形式的gc(r)进行了定性不同的对分布函数测试，并且发现过量实验信号足以排除气体和簇的对分布函数。呈现出溶剂分隔最小值以及可能还有更长程相关性的gc(r)的水合形式，不仅在物理上合理，而且能较好地重现实验数据。这项工作表明，即使在稀浓度下，小角度区域的重要信息也可用于解析溶质 - 溶质相关性、它们的长度尺度以及热力学结果。小角度散射数据所暗示的作用于单个氨基酸侧链微观尺度上的水化力，可能对蛋白质折叠的早期阶段、配体结合以及其他分子间相互作用产生重大影响。
