Forced Kramers escape in single-molecule pulling experiments

The pulling-induced rupture of noncovalent bonds is studied by the overdamped Kramers theory with full account of a time-varying barrier. Mechanic pulling reduces the energy barrier and leads to loading-rate dependence of the rupture force F-u(F-t). Tested against Langevin dynamics, four distinct regimes are identified, including kinetic dominant, weak pulling, strong pulling, and mechanic pulling dominant. Asymptotic analyses show that F-u similar to ln F-t in weak pulling regime and becomes 1-(F-u/F-c)similar to[ln(F-t)/E-b](2/3) in strong pulling regime. Kinetic informations such as activation energy E-b and critical force F-c were extracted from pulling experiments for biotin-streptavidin complex. (C) 2005 American Institute of Physics.