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 Fu (Ft). Tested against Langevin dynamics, four distinct regimes are identified, including kinetic dominant, weak pulling, strong pulling, and mechanic pulling dominant. Asymptotic analyses show that Fu ∼ln Ft in weak pulling regime and becomes 1- (Fu Fc) ∼ [ln (Ft) Eb] 23 in strong pulling regime. Kinetic informations such as activation energy Eb and critical force Fc were extracted from pulling experiments for biotin-streptavidin complex.