Maximal entropy production rates in non-contractile actomyosin

The actin cytoskeleton is an active semi-flexible polymer network whose non-equilibrium properties coordinate both stable and contractile behaviors to maintain or change cell shape. While myosin motors drive the actin cytoskeleton out-of-equilibrium, the role of myosin-driven active stresses in stable states of actomyosin is unclear. To investigate this, we synthesize an actomyosin material in vitro whose active stress content can tune the network from stable to contractile and analyze the resulting filament dynamics using the framework of stochastic thermodynamics. We find that the entropy production rate does not increase monotonically with myosin content, but instead is maximized in a non-contractile, stable state. Our study provides evidence that the origins of system entropy production and activity-dependent dissipation relate to disorder in the molecular interactions between actin and myosin.