Probing active forces via a fluctuation-dissipation relation: Application to living cells

TL;DR

This paper introduces a new fluctuation-dissipation relation for non-equilibrium systems with memory, enabling the measurement of active forces in living cells through experimental data analysis.

Contribution

It presents a novel fluctuation-dissipation relation applicable to non-equilibrium systems with memory, allowing access to active forces in living cells that were previously difficult to measure.

Findings

Identified a crossover time between thermal and active force-driven fluctuations.

Demonstrated that probe position is ultimately governed by active forces.

Provided a method to experimentally access active forces in living cells.

Abstract

We derive a new fluctuation-dissipation relation for non-equilibrium systems with long-term memory. We show how this relation allows one to access new experimental information regarding active forces in living cells that cannot otherwise be accessed. For a silica bead attached to the wall of a living cell, we identify a crossover time between thermally controlled fluctuations and those produced by the active forces. We show that the probe position is eventually slaved to the underlying random drive produced by the so-called active forces.