Activity driven fluctuations in living cells

TL;DR

This paper introduces a model for probe dynamics in living cells that combines thermal fluctuations with nonequilibrium activity, accurately matching experimental data and enabling quantification of cellular activity parameters.

Contribution

The model uniquely integrates active hops within a harmonic potential to describe intracellular probe motion, providing a quantitative framework for cellular activity analysis.

Findings

Model accurately predicts probe statistics in living cells.

Quantitative estimates of activity time scales and fluctuation amplitudes.

Excellent agreement with experimental tracer data.

Abstract

We propose a model for the dynamics of a probe embedded in a living cell, where both thermal fluctuations and nonequilibrium activity coexist. The model is based on a confining harmonic potential describing the elastic cytoskeletal matrix, which undergoes random active hops as a result of the nonequilibrium rearrangements within the cell. We describe the probe's statistics and we bring forth quantities affected by the nonequilibrium activity. We find an excellent agreement between the predictions of our model and experimental results for tracers inside living cells. Finally, we exploit our model to arrive at quantitative predictions for the parameters characterizing nonequilibrium activity, such as the typical time scale of the activity and the amplitude of the active fluctuations.