Effective tension and fluctuations in active membranes

TL;DR

This paper analyzes how nonthermal noise sources affect the fluctuation spectrum of active membranes, considering constraints like area and volume, and compares theoretical results with experimental data.

Contribution

It introduces a comprehensive model for membrane fluctuations under various nonthermal noise sources, accounting for physical constraints and providing new insights into active membrane behavior.

Findings

Membrane tension depends on nonthermal noise characteristics.

External forces and curvature fluctuations influence membrane shape.

Model aligns with experimental observations for certain noise sources.

Abstract

We calculate the fluctuation spectrum of the shape of a lipid vesicle or cell exposed to a nonthermal source of noise. In particular we take into account constraints on the membrane area and the volume of fluid that it encapsulates when obtaining expressions for the dependency of the membrane tension on the noise. We then investigate three possible origins of the non-thermal noise taken from the literature: A direct force, which models an external medium pushing on the membrane. A curvature force, which models a fluctuating spontaneous curvature, and a permeation force coming from an active transport of fluid through the membrane. For the direct force and curvature force cases, we compare our results to existing experiments on active membranes.