Exploring Hysteresis and Energy Dissipation in Single-molecule Force Spectroscopy

We propose an analytical approach to describe the active rebinding and force hysteresis observed in single-molecule pulling experiments. We derive equations for dependences of the measured quantities on the properties of molecular potential, effective stiffness of the pulling spring, and the pulling velocity. The calculations predict that the energy dissipated per an unbinding-rebinding cycle strongly increases with the steepness of the molecular potential and with decreasing the spring stiffness. A comparison of analytical results with Langevin simulations shows that the scaling relations for the barrier heights and most probable forces are more accurate in the case of active rebinding than for unbinding. Our consideration demonstrates that simultaneous analysis of probability density functions for unbinding and rebinding forces improves essentially the accuracy of retrieval information on intrinsic parameters of the molecular complex from the force measurements.