Fluctuation spectrum of fluid membranes coupled to an elastic meshwork: jump of the effective surface tension at the mesh size

TL;DR

This paper models fluid membranes coupled to elastic meshworks, revealing a tension jump at the mesh size that affects membrane fluctuations, with implications for biological membranes and polymer-decorated surfaces.

Contribution

It introduces a model where the elastic meshwork's energy depends on a coarse-grained membrane area, predicting a tension jump at the mesh size scale.

Findings

Predicts a tension jump at the mesh size scale.

Accounts for fluctuation spectra of red blood cell membranes.

Suggests cytoskeleton stress regulates membrane area.

Abstract

We identify a class of composite membranes: fluid bilayers coupled to an elastic meshwork, that are such that the meshwork's energy is a function $F_\mathrm{el}[A_\xi]$ \textit{not} of the real microscopic membrane area $A$, but of a \textit{smoothed} membrane's area $A_\xi$, which corresponds to the area of the membrane coarse-grained at the mesh size $\xi$. We show that the meshwork modifies the membrane tension $\sigma$ both below and above the scale $\xi$, inducing a tension-jump $\Delta\sigma=dF_\mathrm{el}/dA_\xi$. The predictions of our model account for the fluctuation spectrum of red blood cells membranes coupled to their cytoskeleton. Our results indicate that the cytoskeleton might be under extensional stress, which would provide a means to regulate available membrane area. We also predict an observable tension jump for membranes decorated with polymer "brushes".