Bell's expression and the generalized Garg form for forced dissociation of a biomolecular complex.

The dissociation of a biomolecular complex under the action of constant force, constant loading rate, and periodic force is studied theoretically. We show that the celebrated Bell expression provides a good approximation for the bond dissociation rate when F/F(c)<<1, where F(c) is the maxima slope of the binding potential along the reaction coordinate. When 1-F/F(c) <<1 the dissociation rate is better described by a generalized Garg form in which the potential derivative is expanded near F(c). We also show that a constant-force experiment is suitable for extracting the activation energy of the bond, a constant loading experiment is suitable to extract F(c), while time-periodic force can be applied to extract both bond dissociation rates at zero force and F(c).