Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, USA.
J Comput Chem. 2012 Jan 15;33(2):141-52. doi: 10.1002/jcc.21927. Epub 2011 Oct 14.
We present results of molecular dynamics simulations of a model DPPC-water monolayer using charge equilibration (CHEQ) force fields, which explicitly account for electronic polarization in a classical treatment of intermolecular interactions. The surface pressure, determined as the difference between the monolayer and pure water surface tensions at 323 K, is predicted to be 22.92 ±1.29 dyne/cm, just slightly below the broad range of experimental values reported for this system. The surface tension for the DPPC-water monolayer is predicted to be 42.35 ±1.16 dyne/cm, in close agreement with the experimentally determined value of 40.9 dyne/cm. This surface tension is also consistent with the value obtained from DPPC monolayer simulations using state-of-the-art nonpolarizable force fields. The current results of simulations predict a monolayer-water potential difference relative to the pure water-air interface of 0.64 ±0.02 Volts, an improved prediction compared to the fixed-charge CHARMM27 force field, yet still overestimating the experimental range of 0.3 to 0.45 Volts. As the charge equilibration model is a purely charge-based model for polarization, the current results suggest that explicitly modeled polarization effects can offer improvements in describing interfacial electrostatics in such systems.
我们呈现了使用电荷平衡（CHEQ）力场对 DPPC-水单层模型进行分子动力学模拟的结果，该力场在处理分子间相互作用时明确考虑了电子极化。在 323 K 下，通过比较单层和纯水的表面张力来确定表面压力，预测值为 22.92±1.29 达因/厘米，略低于该体系报道的广泛实验值范围。DPPC-水单层的表面张力预测值为 42.35±1.16 达因/厘米，与实验测定的 40.9 达因/厘米值非常吻合。该表面张力也与使用最先进的非极化力场对 DPPC 单层模拟得到的值一致。目前的模拟结果预测单层-水相对于纯水-空气界面的电势差为 0.64±0.02 伏特，与固定电荷 CHARMM27 力场相比有了改进，但仍高估了实验范围 0.3 至 0.45 伏特。由于电荷平衡模型是一种纯粹基于电荷的极化模型，因此目前的结果表明，明确建模的极化效应可以改进对这类体系中界面静电的描述。
