Figure 9:

(A) Schematic of a free energy landscape for an unbinding reaction (black), which with applied force F behaves as either a slip bond (blue) or catch bond (red). For models of a catch bond projected into a 1D reaction coordinate Q, we imagine that application of force creates a new stable minimum which in turn has a higher barrier for transition to the same unbound state. (B) Illustration of catch and slip bond kinetics computed by preliminary MD simulations using infrequent metadynamics⁵² on 2D potentials in pesmd.⁵³ The slip bond potential is a simple double well aligned with the x-axis, with force applied along the x-axis. The catch-bond potential is a modification of the titled double-well potential from Ref. 10, with a third local minimum added in such that the third state becomes the most stable at intermediate force. Dashed lines show fits to Bell’s law for slip-bonds and the two-pathway model for catch bonds.⁵⁴