Active Forces in Polymer Physics

Biological processes frequently require spatial and temporal coordination of numerous proteins and nucleic acids whose motion is driven by stochastic forces. Brownian forces that arise from thermal fluctuations exhibit properties that are defined by the dissipation of heat through friction (so called fluctuation-dissipation theorem), resulting in dynamic behavior that is fully consistent with equilibrium thermodynamics.

Living cells and other non-equilibrium systems are driven from their equilibrium state by chemical reactions and external perturbations that contribute active forces, resulting in behavior that is reminiscent of Brownian motion yet cannot be precisely analyzed using the existing theoretical framework. Therefore, the guiding principles for active-Brownian motion need to be defined to effectively predict and analyze the dynamic behavior in living cells and other systems that are driven away from equilibrium. We work on both an exact analytical treatment of the dynamic behavior of a polymer chain that is subjected to both thermal and active forces as well as understanding from molecular simulations perspective. Our model for active forces incorporates temporal correlation associated with the characteristic time scale and processivity of enzymatic function, leading to an active time scale that competes with relaxation processes within the polymer chain.