Figure 2. Structural stability of δ-crystallin. The labels represent the protein samples of wild-type (○) and E294L (●). A: Thermostability. The ellipticity at 222 nm was monitored at various temperatures. B: Stability in the presence of Gdm-HCl. Tryptophan fluorescence was measured in response to various concentrations of Gdm-HCl. The solid lines were obtained from the result of global fitting to the equation based on a 4-state model [15]. The protein concentrations used in the assays were 0.5 mg/ml for (A) and 0.03 mg/ml for (B).