Fig. 3.

Least-squares fits of experimental C_α/C_β crosspeak shapes to two-state and two-step models (see Results) for the conformational distribution of HP35 near its denaturation midpoint. (a) [Gdn·HCl] = 4 M. Folded fractions f_fold derived from the fits are 0.48 ± 0.04 and 0.50 ± 0.05 for the two-state and two-step models, respectively. (b) [Gdn·HCl] = 5 M. Folded fractions are 0.05 ± 0.05 and 0.00 ± 0.05 for the two-state and two-step models, respectively. The two-step model represents the crosspeak shapes accurately, whereas the simple two-state model does not.