Molecular dynamics simulation of hydrated DPPC monolayers using charge equilibration force fields

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 ±1.29dyne/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 ±1.16dyne/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. © 2011 Wiley Periodicals, Inc. J Comput Chem, 2011