Figure 4.

Analysis of DFS data using Eq. 5 for (a) biotin-streptavidin and (b) biotin-avidin. For each ν, the fits, residuals ($|f_{fit}^{*}-f_{exp}^{*}|/f_{exp}^{*}\times 100$), and extracted parameters were summarized in the table on the right. We can draw some general conclusions from the fits. For the biotin-streptavidin complex, fit with ν = 0.397 produces the smallest errors although at high loading rates the relative errors for ν = 0.397 and ν = 0.5 are comparable. There are variations in other parameters (x^‡, G^‡, and κ) for all ν. For the biotin-avidin complex, the situation is far worse. In particular, the relative errors in the fits are large even when ν is varied. Similarly, the parameters extracted from the fits are not totally consistent. Taken together, the fits using a 1D free energy profile with a single barrier is not appropriate to describe the rupture kinetics of these two complexes.