Fig. 5. Folding criteria (i.e. cutoffs) were selected without knowledge of the experimental folding rate. The rate constants were fit to the linear increase in the folded population of TZ1 (a), TZ2 (b), and TZ3 (c) by using a range of cutoffs: symmetric beta structure and RMSD_cα of 1.4 Å (black filled circles), 1.6 Å (gray filled circles), or 1.8 Å (open circles), at which folding was taken to be irreversible. The unfolding rate constants for TZ1 (d), TZ2 (e), and TZ3 (f) were fit at each temperature, 296K (black filled circles), 319K (open circles), and 343K (triangle), by using a range of cutoffs (RMSD_cα + 0.125 L < 9.5 ± 0.5) which affect the unfolding rate only slightly. We can determine the temperature dependence of unfolding TZ1 (black filled circles), TZ2 (gray filled circles), and TZ3 (open circles) with an Arrhenius plot (g).