Fig. 4.

Double logarithm plot of the two unfolding rate constants for different three-state proteins, including mutational variants of PDZ2 (this work) and of R16 (28), and different proteins available in literature, including the Engrailed homeodomain (7), tendamistat (23), the FF domain in the presence/absence of sulfate (39), cytochromes c₅₅₂ from Thermus termophilus and Hydrogenobacter termphilus at three different pH values (refs. 40 and 41 and unpublished data), Im7 (42), acil-CoA binding protein (43), lysozyme (44), B1 domain of protein G (45), horse cytochrome c (46), and a stabilized three-state mutant of cytochrome c from Pseudomonas aeruginosa (47). The line is the best fit to a linear function (R = 0.94).