Hydrodynamic effects on spinodal decomposition kinetics in planar lipid bilayer membranes

Abstract

The formation and dynamics of spatially extended compositional domains in multicomponent lipid membranes lie at the heart of many important biological and biophysical phenomena. While the thermodynamic basis for domain formation has been explored extensively in the past, domain growth in the presence of hydrodynamic interactions both within the (effectively) two-dimensional membrane and in the three-dimensional solvent in which the membrane is immersed has received little attention. In this work, we explore the role of hydrodynamic effects on spinodal decomposition kinetics via continuum simulations of a convective Cahn-Hilliard equation for membrane composition coupled to the Stokes equation. Our approach explicitly includes hydrodynamics both within the planar membrane and in the three-dimensional solvent in the viscously dominated flow regime. Numerical simulations reveal that dynamical scaling breaks down for critical lipid mixtures due to distinct coarsening mechanisms for elongated versus more isotropic compositional lipid domains. The breakdown in scaling should be readily observable in experiments on model membrane systems.

A finite element approach to incompressible two-phase flow on manifolds

“…However, the numerical treatment is restricted to simplified geometries, e.g. an axisymmetric setting (Arroyo & DeSimone 2009) or a planar interface (Fan et al 2010). Such special cases circumvent the subtleties in describing vectorial second-order partial differential equations on curved domains.…”

“…in emulsions or liquid phases in cell membranes, there is now also a need for an efficient numerical treatment of the equations. Within the context of cell membranes the model has been considered, for example, in Hu, Zhang & E (2007), Arroyo & DeSimone (2009) and Fan, Han & Haataja (2010). However, the numerical treatment is restricted to simplified geometries, e.g.…”

Critical point fluctuations in supported lipid membranes

“…The non-exact correspondence to the 2D Ising model may be due to fluid hydrodynamic effect on the domain formation kinetics and also that of the substrate. Recent work by Haataja [37][38][39] shows theoretically that large fluctuations in compositional domains will induce the flow of lipid components and domain structures, thereby inducing flow fields in the surrounding fluid. The water is not a passive structure, its motion interacts and couples with the membrane, changing its behaviour.…”

Transient domain formation in membrane-bound organelles undergoing maturation

“…The role of hydrodynamics on phase separation in fluid membranes is still controversial, despite considerable recent attention [14,27]. For off-critical mixtures (φ = 1/2), hydrodynamic correlations result in the diffusion and coalescence of entire domains.…”

“…In the context of fluid membranes, hydrodynamic flows in the membrane and the surrounding media make the problem quite complex. Several dynamical regimes have been reported, and a unified picture of has not yet emerged [13,14]. For deformable fluid membranes such as cellular membranes, the budding of membrane domains [15] makes the dynamics of phase separation even more complex [16][17][18].…”