Efficient Simulation of Tunable Lipid Assemblies Across Scales and Resolutions.

We present a minimal model for simulating dynamics of assorted lipid assemblies in a computationally efficient manner. Our model is particle-based and consists of coarse-grained beads put together on a modular platform to give generic molecular lipids with tunable properties. The interaction between coarse-grained beads is governed by soft, short-ranged potentials that account for the renormalized hydrophobic effect in implicit solvent. The model faithfully forms micelles, tubular micelles, or bilayers (periodically infinite, bicelles, or vesicles) depending on the packing ratio of the lipid molecules. Importantly, for the self-assembled bilayer membranes it is straightforward to realize gel and fluid phases, the latter of which is most often of primary interest. We show that the emerging physics over a wide range of scales and resolutions is (with some restrictions) universal. The model, when compared to other popular lipid models, demonstrates improvements in the form of increased numerical stability and boosted dynamics. Possible strategies for customizing the models (e.g., adding chemical specificity) are briefly discussed. An implementation is available for the LAMMPS molecular dynamics simulator [Plimpton. J. Comp. Phys. 117, 1-19. (1995)] including illustrative input examples from the simulations we present.