Fig. 4.

Projection of free energy onto d₁₂ and d₁₆ (contour lines are separated by 0.5 kcal/mol). The points overlayed on the plot correspond to the structures from which the committors were estimated. Color coding: red, tends not to unfold (0 ≤ P_u < 0.35); white, “transition state” (0.35 ≤ P_u ≤ 0.65); black, tends to unfold (0.65 < P_u ≤ 1.0). During the estimation, the unfolded state was defined as d₁₂ > 10.75 and d₁₆ > 11. Only structures that reached a stable state were counted in the estimation of P_u. The other stable states were defined as the native state (d₁₂ < 9.0; 5.5 < d₁₆ < 8.0), G6 unfolds (d₁₂ < 7.0; 8.0 < d₁₆ < 18), and the stacked state (6.0 < d₁₂ < 9.0; d₁₆ < 5.5). The region marked with the rectangle has been identified as the “transition state region” (see Fig. 5). The qualitative distribution of committor values and location of the transition-state region are relatively insensitive to the definitions of the stable and transition states.