Effects of active noise on transition-path dynamics

We propose an extension of the existing model describing a biomolecular reaction such as protein folding or ligand binding which is usually visualised as the barrier crossing of a diffusing particle in a double-well potential. In addition to the thermal noise, an active noise modelled in terms of an Ornstein–Uhlenbeck process is introduced to the dynamics. Within this framework, we investigate the transition-path properties of an underdamped particle surmounting an energy barrier, and we show explicitly how these properties are affected by the activity and persistence of the particle. Our theoretical study suggests that an active particle can cross the barrier at comparatively shorter timescales by lowering the (effective) barrier height. In particular, we study how the persistence time of the active force alters the transition-path time (TPT) at different friction limits. Interestingly, in one of our models we find a nonmonotonic behaviour of the TPT which is absent in the overdamped limit. The framework presented here can be useful in designing a reaction in a non-equilibrium environment, particularly inside a living biological cell in which active fluctuations keep the system out of equilibrium.