When simulating a molecular system at the interface between two phases, such as in protein-adsorption, the molecular environment in the interfacial region may be sufficiently different from the individual phases (bulk solution, surface) as to require the use of a distinct set of parameters for interfacial interactions. Recently published simulations of peptide adsorption to surfaces using the CHARMM force field have demonstrated this issue by revealing that calculated values of adsorption free energy substantially differ from experimental results. To address this problem, we have developed a dual-force-field approach in the CHARMM program that uses two distinct sets of nonbonded parameters within the same simulation: one for intra-phase interactions and one for inter-phase interactions. Using this approach, interfacial parameters can be adjusted to correct errors in peptide adsorption free energy without altering peptide conformational behavior in solution, enabling accurate modeling of both intra- and inter-phase behavior in the same simulation.

Modeling multiphase systems with independent  force fields controlling intra- and inter-phase interactions

243rd National Meeting (2012)

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