Department of Chemistry, Stanford University , Stanford, California 94305, United States.
J Phys Chem B. 2013 Dec 19;117(50):16236-48. doi: 10.1021/jp410720y. Epub 2013 Dec 10.
The electric field created by a condensed-phase environment is a powerful and convenient descriptor for intermolecular interactions. Not only does it provide a unifying language to compare many different types of interactions, but it also possesses clear connections to experimental observables, such as vibrational Stark effects. We calculate here the electric fields experienced by a vibrational chromophore (the carbonyl group of acetophenone) in an array of solvents of diverse polarities using molecular dynamics simulations with the AMOEBA polarizable force field. The mean and variance of the calculated electric fields correlate well with solvent-induced frequency shifts and band broadening, suggesting Stark effects as the underlying mechanism of these key solution-phase spectral effects. Compared to fixed-charge and continuum models, AMOEBA was the only model examined that could describe nonpolar, polar, and hydrogen bonding environments in a consistent fashion. Nevertheless, we found that fixed-charge force fields and continuum models were able to replicate some results of the polarizable simulations accurately, allowing us to clearly identify which properties and situations require explicit polarization and/or atomistic representations to be modeled properly, and to identify for which properties and situations simpler models are sufficient. We also discuss the ramifications of these results for modeling electrostatics in complex environments, such as proteins.
凝聚相环境产生的电场是描述分子间相互作用的一种强大而方便的描述符。它不仅提供了一种统一的语言来比较许多不同类型的相互作用，而且还与实验可观察量，如振动斯塔克效应，具有明确的联系。我们使用 AMOEBA 极化力场的分子动力学模拟，在此计算了一系列具有不同极性的溶剂中振动生色团（苯乙酮的羰基）所经历的电场。计算电场的平均值和方差与溶剂诱导的频率位移和带宽很好地相关，表明斯塔克效应是这些关键溶液相光谱效应的基础机制。与固定电荷和连续模型相比，AMOEBA 是唯一一种能够以一致的方式描述非极性、极性和氢键环境的模型。然而，我们发现固定电荷力场和连续模型能够准确地复制极化模拟的一些结果，这使我们能够清楚地识别哪些性质和情况需要进行明确的极化和/或原子表示来进行适当建模，并确定哪些性质和情况简单模型就足够了。我们还讨论了这些结果对在复杂环境（如蛋白质）中建模静电的影响。
