Force Modulating Dynamic Disorder: Physical Theory of Catch-slip bond Transitions in Receptor-Ligand Forced Dissociation Experiments

摘要

Recently experiments showed that some adhesive receptor-ligand complexesincrease their lifetimes when they are stretched by mechanical force, while theforce increase beyond some thresholds their lifetimes decrease. Severalspecific chemical kinetic models have been developed to explain the intriguingtransitions from the "catch-bonds" to the "slip-bonds". In this work we suggestthat the counterintuitive forced dissociation of the complexes is a typicalrate process with dynamic disorder. An uniform one-dimension force modulatingAgmon-Hopfield model is used to quantitatively describe the transitionsobserved in the single bond P-selctin glycoprotein ligand1(PSGL-1)$-$P-selectin forced dissociation experiments, which were respectivelycarried out on the constant force [Marshall, {\it et al.}, (2003) Nature {\bf423}, 190-193] and the force steady- or jump-ramp [Evans {\it et al.}, (2004)Proc. Natl. Acad. Sci. USA {\bf 98}, 11281-11286] modes. Our calculation showsthat the novel catch-slip bond transition arises from a competition of the twocomponents of external applied force along the dissociation reaction coordinateand the complex conformational coordinate: the former accelerates thedissociation by lowering the height of the energy barrier between the bound andfree states (slip), while the later stabilizes the complex by dragging thesystem to the higher barrier height (catch).