Hydrodynamics of quantized shape transitions of lipid domains

Abstract

The time-dependent distortions of nearly circular liquid domains of lipids at the air-water interface are studied analytically by accounting for line tension and electrostatic effects in the monolayer and viscous effects in both the monolayer and subphase fluid. One driving force for the shape changes arises from the elec­trostatic repulsions between molecular dipoles. This force is opposed by a line tension that favors circular shapes. The growth rate of small amplitude disturbances is determined as a function of the distortion (azimuthal) symmetry number n , the domain radius, the dipole density difference and line tension between the lipid domain and the surrounding lipid layer, and the viscosities of the monolayer and underlying liquid. For representative parameter values, the disturbance growth rate is independent of the monolayer viscosity and depends only on the subphase viscosity.