Comparison of Biomolecular Force Fields for Alkanethiol Self-Assembled Monolayer Simulations

Abstract

Reasonable all-atom or united-atom biomolecular force fields have been developed to represent the properties of proteins and lipid membranes in molecular dynamics simulations. However, since they have not been parametrized for self-assembled monolayers (SAMs), their utility in simulating SAMs and protein–SAM systems has not been confirmed. Here, we compared six popular biomolecular force fields, Lipid14, GAFF, L-OPLS, CHARMM36, Slipids, and GROMOS54a7, to simulate alkanethiol SAMs of short to long chains (C10–C18). Our results show that none of these force fields reproduce the chain length dependence of the tilt angle, and twist angle. Although the droplet contact angles on SAMs are well represented by all force fields, only GAFF and Lipid14 yield phase transition temperatures that are reasonably close to the experimental values. Overall, our comprehensive comparison suggests that GAFF and Lipid14 are better choices for SAM simulations; further improvements in the force field parameters for SAMs are requi...