Dynamic response of adhesion complexes: Beyond the single-path picture

We analyze the response of molecular adhesion complexes to increasing pulling forces (dynamic force spectroscopy) when dissociation can occur along either one of two alternative trajectories in the underlying multidimensional energy landscape. A great diversity of behaviors (e.g., nonmonotonicity) is found for the unbinding force and time as a function of the rate at which the pulling force is increased. In particular we identify a class of "harpoon" stickers that bind easily but resist strong pulling efficiently. Using existing data, we also demonstrate the consequent difficulty of unambiguously determining the features of the energy landscape from such single-molecule pulling experiments.