Numerical investigations of the dynamics of two-component vesicles

Abstract

We examined the dynamics of the deformation and phase separation of two-componentvesicles. First, we numerically investigated the effects of (i) thermal noise, (ii)hydrodynamic flow induced by the line tension of the domain boundary and (iii)composition-dependent bending rigidity on the coarsening dynamics of a phase-separatedpattern on the surfaces of vesicles with fixed shapes. The dynamical exponentz (NDB ∼ t − z, the total length of the domain boundaries) of the coarseningof the phase-separated pattern was found to decrease fromz = 1/3 under nothermal noise to 1/5 < z < 1/4 when including the effects of thermal noise. We also found that the hydrodynamiceffect enhances the coarsening in a bicontinuous phase separation for a sphericalvesicle. In phase separations of a shape-fixed tubular vesicle, a band-like phaseseparation with periodicity along the longer axis of the tube occurs because of thecomposition-dependent bending rigidity and the higher curvatures at the tube end-caps.Second, we also explored the dynamics of shape deformation coupled with phaseseparation through the bending rigidity of the membrane which depends on thelocal composition in lipids and found that the composition-dependent bendingrigidity crucially influences the phase separation and deformation of the vesicle.The results of simulations are in good agreement with experimentally observedbehavior known as ‘shape convergence’ (Yanagisawa et al 2008 Phys. Rev. Lett. 100148102).