Motor-free Contractility in Active Gels

Force generation in animal cells is usually due to molecular motors. Recent experimental evidences, however, have implied that contractility can be generated in the absence of motors. In this talk, we propose a motor-free mechanism that generates contraction in biopolymer networks. Unlike motors which rely on polar substrate for their functions, our mechanism is based on the asymmetric force-extension relation of semiflexible biopolymers. Together with active binding and unbinding of crosslinkers, this asymmetry leads to a nonthermal, ratchet-like process that generate steady-state contraction. Our mechanism may provide an explanation for the motor-independent contractility observed in living cells.