Kinesin operates as a Maxwell demon to leverage nonequilibrium fluctuations

Nanoscale molecular machines are composed of strongly interacting parts, operate with energy scales comparable to the thermal energy k_BT, and are subject to stochastic fluctuations. As such, information is a relevant free energy resource, enabling molecular machines to interconvert between information and other forms of free energy. Recent experiments demonstrate that information engines—designed to convert between information and stored energy—can achieve performance comparable to biological molecular machines. However, whether biological molecular machines use information to operate as Maxwell demons in vivo remains an open question. Building on recent theoretical advances showing that information flows are required to extract work from different sources of fluctuations, and experimental observations that kinesin operates faster when subject to nonequilibrium noise, we investigate the stochastic thermodynamics of kinesin motors pulling cargo in the presence of nonequilibrium fluctuations. We show that kinesin can operate as a Maxwell demon to leverage nonequilibrium noise, and introduce a novel statistical estimator capable of quantifying this behavior from limited experimental data. Our results establish a path to reliably identify Maxwell demons in biological systems.