Most importantly, all Φ-values in this work have been determined using refolding data only, to avoid any uncertainty that might arise from fits of the unfolding data. Also, to avoid a long extrapolation to 0 M denaturant27 and to eliminate any possible effects of aggregation, all Φ-values were calculated at 2 M urea. We show (Supplementary Data Fig. S 4) that the Φ-values determined using either linear or Hammond fits of the data are essentially identical. Thus, despite the complexity of the analysis, the Φ-values obtained are reproducible. The results of the kinetic analysis are shown in Tables 2 and 3.