An efficient multiparticle collision dynamics approach to immiscible binary fluids: Hydrodynamics and application to membrane protein diffusion

We present a multiparticle collision dynamics (MPC) implementation of layered immiscible fluids A and B of different shear viscosities separated by planar interfaces^[1]. The simulated shear flow profile, and the time-dependent shear stress functions, are in excellent agreement with our continuum hydrodynamics results for the composite fluid. The wave-vector dependent transverse velocity auto-correlation functions in the bulk-fluid regions of the layers decay exponentially, and agree with those of single-phase isotropic MPC fluids. In addition, we determine the hydrodynamic mobilities of an embedded colloidal sphere moving steadily parallel or perpendicular to a fluid-fluid interface, as functions of the distance from the interface. The obtained mobilities are in good agreement with hydrodynamic force multipoles calculations for a no-slip sphere moving under creeping flow conditions near a clean, ideally flat interface. Moreover, we discuss our preliminary simulation results for a simple model of G protein-coupled receptors diffusing alongside a coarse-grained membrane based on a layered binary fluid model. The results show that this model is computationally efficient and feasible to study the diffusion of interacting membrane proteins over extended time and length scales^[2].