Bringing calorimetry (back) to life

TL;DR

This paper introduces a framework for nonequilibrium micro-calorimetry in biological systems, demonstrating how heat capacity depends on biophysical parameters and can exhibit negative values due to biological activity.

Contribution

It develops the conceptual framework of nonequilibrium calorimetry and applies it to biophysical models, revealing novel dependencies of heat capacity on biological parameters.

Findings

Heat capacity can be negative due to biological activity.

Heat capacity depends intriguingly on biophysical parameters.

Nonequilibrium calorimetry offers insights into biological systems.

Abstract

Micro-calorimetry offers significant potential as a quantitative method for studying the structure and function of biological systems, for instance, by probing the excess heat released by cellular or sub-cellular structures, isothermal or not, when external parameters change. We present the conceptual framework of nonequilibrium calorimetry, and as illustrations, we compute the heat capacity of biophysical models with few degrees of freedom related to ciliar motion (rowing model) and molecular motor motion (flashing ratchets). Our quantitative predictions reveal intriguing dependencies of the (nonequilibrium) heat capacity as a function of relevant biophysical parameters, which can even take negative values as a result of biological activity.