Prolonged lifetime of a dispersing membrane domain

Membrane heterogeneities on the scale of tens of nanometers appear in many cellular functions. We study the Brownian motion of an assembly of inclusions embedded in a fluid membrane. The motion consists of the dispersal of the assembly into the background lipid membrane, accompanied by the diffusion of its center of mass. Usually, dispersal is much faster than collective motion, since the diffusion coefficient of the center of mass is inversely proportional to the number of particles. In the case of membrane inclusions, we find that the two processes occur on the same time scale, thus prolonging significantly the lifetime of the assembly as a compact mobile object. This strong correlation effect is caused by quasi-two-dimensional membrane flows, which couple the motions even of the most remote inclusions in the assembly. The same correlations cause the diffusion coefficient of the center of mass to decay slowly with time, leading to weak sub-diffusion of the assembly. We confirm the analytical results by Brownian Dynamics simulations with hydrodynamic interactions. The generic flow-mediated effect should be dominant at distances larger than the molecular scale, thus prolonging the stability and collective motion of membrane nano-domains.