A simple mechanical model for synthetic catch bonds

Catch bonds are protein-ligand bonds which become more difficult to break as the applied force increases, a counterintuitive phenomenon that has not yet been reproduced in synthetic systems. Here, we have demonstrated that a simple mechanical design based on a tweezer-like mechanism can exhibit catch bond characteristics under thermal excitations. The tweezer has a force-sensitive switch which controls the transition of the system to a high-ligand-affinity state with additional ligand-tweezer interactions. Applying kinetic theory to a two-mass-two-spring idealized model of the tweezer, we show that by tuning the shape of the switch and the ligand-tweezer interaction energy landscapes, we can achieve greater lifetimes at larger force levels. We validate our theory with molecular dynamics simulations and produce a characteristic lifetime curve reminiscent of catch bonds. Our analysis reveals minimal design guidelines for reproducing the catch bond phenomenon in synthetic systems such as molecular switches/foldamers, DNA linkers, and nanoparticle networks.