Fig. (11) Structural stability of HT7 and HT2. A. Temperature dependence of CD signal at 224 nm. Denaturation temperatures (Tm) were determined by fitting the data to a simple two-state transition model. B. Effect of urea on ligand binding activity. Proteins were exposed to urea for 16 h at 25 °C and the amount of properly folded protein remaining (relative to no treatment) was calculated based on sensitivity to thermolysin-induced proteolysis [26].