Figure 1.

Schematic free energy profile for models used to account for curvature in unfolding (and possibly also refolding) arms of chevrons. In all panels the profile is shown for folding conditions (solid line, A), mild denaturing conditions (long-dashed line, B), and strongly denaturing conditions (short-dashed line, C). (A) Change in ground state/population of an unfolding intermediate. As the concentration of urea is increased, N* becomes stable relative to N and thus becomes the ground state for folding. (B) Broad transition state model; folding takes place relatively isoenergetically across a broad energy barrier. (C) Sequential transition state model. Folding transition states are narrow along this reaction observable (β_T) (Oliveberg 1998, 2001; Otzen and Oliveberg 2002; Sanchez and Kiefhaber 2003a; Seeliger et al. 2003).