ABSTRACT
This chapter introduces the basis for the force-induced unbinding experiments carried out by atomic force microscopy (AFM). In many biochemical processes, the bond rupture is induced by external forces. According to the transition state theory, the external force tilts the energy landscape, that is, decreases the energy barrier height. In the Bell–Evans model applied to the AFM measurements only the position of the energy barrier and the dissociation rate constant can be estimated. The Bell–Evans approach is the oldest and most widely applied model describing the unbinding of single molecular complexes. In the Dudko–Hummer–Szabo model, the single molecular complexes unbinding is described by a harmonic free-energy potential with a single sharp energy barrier. Studies of the adhesive properties in living cells require the application of protocols that are used to modify surfaces of both cantilevers and substrates. Qualification of adhesive properties by means of AFM is usually carried out in the force spectroscopy mode, where force curves are recorded.
