Equilibrium fluctuations of a quasi-spherical vesicle: role of the membrane dissipation

TL;DR

This paper presents a theoretical study of thermally-driven fluctuations in quasi-spherical vesicles, highlighting how membrane viscosity influences their dynamic behavior and relaxation processes.

Contribution

It introduces a model that incorporates dissipation from monolayer viscosity and intermonolayer friction to predict fluctuation dynamics in vesicles.

Findings

Membrane curvature affects long-wavelength undulation relaxation.

Lipid density fluctuations are accelerated by membrane viscosity.

A stretched-exponential relaxation regime may not be present in vesicles.

Abstract

We theoretically investigate the thermally-driven curvature and lipid density fluctuations of a quasi-spherical vesicle, accounting for the dissipation due to monolayer viscosity and intermonolayer friction. The theory predicts that membrane curvature makes long-wavelength undulations sensitive to membrane viscosity and speeds up the relaxation of the lipid density fluctuations. Implications for the dynamic roughness and Dynamic Structure Factor measurements of submicron liposomes on nano-second time scales are discussed. Specifically, a clear stretched-exponential relaxation regime may not exist, in contrast to the behavior of planar membranes for which an anomalous diffusion exponent of 2/3 has been predicted [Zilman and Granek, Phys. Rev. Lett. (1996)].