Figure 3.

Contour plots of the two-dimensional free energy surface (in units of k_BT_f) as a function of approach distance and contact ordering fraction Q_p. ΔR = R − R₀ is the separation distance relative to that of the bound complex (R₀). The steepest descent paths are shown for the unfolded (red) and folded (green) states. At T_f, far from the binding site, the folded and unfolded structures are equally favorable. At ΔR = 20 Å, the unfolded state already feels the interaction falling to a lower contour while the folded state remains unaffected by the binding interaction. Q_p for the unfolded ensemble hardly increases until ΔR = 8 Å, whereupon the free energy falls dramatically, while Q_p increases by about 0.2. Closer in, the unfolded trajectory completes folding rapidly with binding. Parameters and broken scale in R are same as in Fig. 2.