Fluctuations in active membranes

TL;DR

This paper reviews experimental and theoretical methods to analyze active membrane fluctuations driven by metabolic energy, emphasizing the importance of combining fluctuation data with mechanical response measurements to distinguish active from thermal effects.

Contribution

It introduces integrated approaches for quantifying active forces in membranes, highlighting the need to go beyond classical thermal fluctuation analysis for accurate characterization.

Findings

Active forces influence membrane fluctuations and mechanical properties.

Combining fluctuation and response measurements helps isolate active contributions.

Refined models improve understanding of active membrane dynamics.

Abstract

Active contributions to fluctuations are a direct consequence of metabolic energy consumption in living cells. Such metabolic processes continuously create active forces, which deform the membrane to control motility, proliferation as well as homeostasis. Membrane fluctuations contain therefore valuable information on the nature of active forces, but classical analysis of membrane fluctuations has been primarily centered on purely thermal driving. This chapter provides an overview of relevant experimental and theoretical approaches to measure, analyze and model active membrane fluctuations. In the focus of the discussion remains the intrinsic problem that the sole fluctuation analysis may not be sufficient to separate active from thermal contributions, since the presence of activity may modify membrane mechanical properties themselves. By combining independent measurements of spontaneous fluctuations and mechanical response, it is possible to directly quantify time and energy-scales of the active contributions, allowing for a refinement of current theoretical descriptions of active membranes.