Figure 2.

The funnel free-energy profile in the capillarity approximation. The solid curve is the ideal profile of the free energy versus the folded fraction, assuming no heterogeneity of stabilization energy. An actual profile differs by a fluctuation that is random and Gaussianly distributed due to this heterogeneity. This is the “fine structure” of the folding funnel. A specific such profile is indicated by a dotted line. Notice the cusp-like minima occur at precisely Ñ_f = 0 and Ñ_f = 1, because the capillarity theory is an asymptotic result for large N_TOT. Simulations and mean field theory show smooth minima at nonextreme values of the order parameters.