Analyzing friction forces with the Jarzynski equality

Abstract

We investigate the applicability of the Jarzynski equality for reconstructing the energy landscape from force measurements obtained in single molecular unbinding and friction experiments. We demonstrate that single-well molecular potentials, such as the Lennard-Jones potential, could be accurately recovered using a reasonable number of force traces (∼100) obtained for velocities which are experimentally accessible, v≈5-100nm s-1. The situation becomes more complex in the presence of potential barriers in the energy profile. These include the double-well and periodic potentials that we consider here. The slow convergence of the reconstruction procedure results from a large energy dissipation which occurs during jumps across the potential barriers. We suggest a modification of the reconstruction procedure which allows the recovering of the correct shape of the potential wells even in the presence of potential barriers. However, a reconstruction of the potential shape in the vicinity of potential maxima requires additional information. © 2008 IOP Publishing Ltd.