The internal states of active inclusions and the dynamics of an active membrane

TL;DR

This paper presents a theoretical model of active inclusions in a membrane, revealing how activity levels influence membrane stability, domain formation, and fluctuation spectra, with implications for understanding active biological membranes.

Contribution

It introduces a novel theoretical framework incorporating active inclusion states and their effects on membrane dynamics and stability, extending previous passive membrane models.

Findings

High activity causes membrane instability and aggregation.

Active conformational changes induce finite size domains.

Stable membranes exhibit a modified fluctuation spectrum with an effective temperature.

Abstract

A theoretical model of a two-component fluid membrane containing lipids and two-state active inclusions is presented. Under strong inclusion activities the membrane can be unstable due to pump-driven undulation or aggregation of high curvature excited inclusions. Depending on the structural details of the inclusions, the active conformation change of the inclusions can also induce finite size domains on the membrane. At long wavelengths a stable membrane has a height fluctuation spectrum similar to previous studies which neglected the inclusion internal states. For a tensionless membrane, $<h({\bf q}_{\perp}, t)h(-{\bf q}_{\perp}, t)> \sim T_{eff} q_{\perp}^{-4}$, where $T_{eff}$ is an effective temperature which depends on the details of inclusion activities.