ABSTRACT
Here r D represents the inverse of the diffusion-limited attempt frequency, E0 is the depth of energy well and xp is the distance to the transition state. Immediately, we can see from equation (26) that the pull-off force increases logarithmically as the loading rate r f increases. Thus, bond strength can vary quite significantly over a wide range of loading rates. Moreover, the slope of this dependence provides the value of the distance to the potential barrier, xp. Evans and co-workers [48] demonstrated this behavior in a dynamic force spectroscopy experiment by measuring the interaction between biotin ligands and avidin or streptavidin proteins over many decades of loading rate (Fig. 4). Subsequently, researchers used dynamic force spectroscopy to study energy landscapes of single bonds for a number of interactions between biological and chemical species, such as DNA [49, 50], RNA [51], proteins and ligands [52, 53] and enzymes and drugs [54]. Table 2 summarizes some of these results.
