Effective Temperature of Red Blood Cell Membrane Fluctuations

TL;DR

This paper investigates the concept of effective temperature in non-equilibrium biological fluctuations, specifically in red blood cell membranes, revealing how different measures can contradict and how physical motor properties can be inferred.

Contribution

It provides a theoretical framework comparing non-Gaussianity and effective temperature, and applies it to experimental data on red blood cell membrane fluctuations to infer motor characteristics.

Findings

Effective temperature can be frequency dependent and higher than ambient temperature.

Non-Gaussianity and effective temperature measures can contradict each other.

Experimental data can reveal the physical nature of motors in cell membranes.

Abstract

Biologically driven non-equilibrium fluctuations are often characterized by their non-Gaussianity or by an "effective temperature", which is frequency dependent and higher than the ambient temperature. We address these two measures theoretically by examining a randomly kicked "particle", with a variable number of kicking "motors", and show how these two indicators of non-equilibrium behavior can contradict. Our results are compared with new experiments on shape fluctuations of red-blood cell membranes, and demonstrate how the physical nature of the motors in this system can be revealed using these global measures of non-equilibrium.