Nanoscale surface relaxation of a membrane stack

TL;DR

This paper investigates the dynamic surface relaxation modes of membrane stacks, identifying a slow overdamped capillary mode influenced by surface tension and viscosity, which helps in understanding membrane fluctuation behaviors.

Contribution

It introduces a model explaining the slow relaxation mode in membrane stacks as an overdamped capillary wave, linking it to measurable physical parameters.

Findings

The slow relaxation mode is due to an overdamped capillary wave.

Surface tension and anisotropic viscosity influence the relaxation dynamics.

Method to extract dynamic surface tension from fluctuation measurements.

Abstract

Recent measurements of the short-wavelength (~ 1--100 nm) fluctuations in stacks of lipid membranes have revealed two distinct relaxations: a fast one (decay rate of ~ 0.1 ns^{-1}), which fits the known baroclinic mode of bulk lamellar phases, and a slower one (~ 1--10 \mu s^{-1}) of unknown origin. We show that the latter is accounted for by an overdamped capillary mode, depending on the surface tension of the stack and its anisotropic viscosity. We thereby demonstrate how the dynamic surface tension of membrane stacks could be extracted from such measurements.