Mesoscopic membrane simulations with mbtools

Figure 1: The lipid model. This tutorial introduces the mbtools package, which provides an ESPRESSO implementation of the mesoscopic membrane model of Cooke et al.1 This coarse grained (CG) model has a fairly low resolution (three beads per lipid molecule) and, moreover, eliminates the embedding solvent entirely. While not being a good choice for questions that depend critically on chemically specific aspects of lipid molecules, it nevertheless self-assembles into fluid lipid bilayers that show the correct curvature elastic behavior on large2 scales with physically meaningful and tunable elastic parameters. The present tutorial is not the right place to discuss much of the physical basis of both the model and its emerging physical behavior, and therefore the reader is encouraged to read up on this in a recent review article.3 Instead, we will illustrate how the mbtools package can be used to efficiently work with this model in the context of ESPRESSO, and along the line learn a bit about the model’s capabilities. Specific aspects of lipid bilayer physics we will look at are bilayer self-assembly, measuring the membrane edge tension, and determining both the mean and the Gaussian curvature modulus. References to pertinent literature will be given alongside.