Fig. 1. (A) Far-UV CD spectra of the F34W/W14F mutant and wild type SNase under different conditions. Protein concentration was 0.3 mg/ml in 30 mM Tris-HCl, pH 7.4. The spectra were measured at 25°C, and the sample cell pathlength was 0.1 mm. (bold line) F34W/W140F; (thick line) F34W/W140F in the presence of 60 mM pdTp and 10 mM Ca²⁺; (------) wild type SNase; (--·--) wild type SNase in 6 M GuHCl. (B) Near-UV CD spectra of the F34W/W140F, F34W, and W140F mutants and wild type SNase under different conditions. Protein concentration is 1.0 mg/ml in 30 mM Tris-HCl, pH 7.4. The spectra were measured at 25°C, and the sample cell pathlength was 10 mm. (thick line) F34W/W140F; (thin line) wild type SNase; (------) F34W; (--··) W140F; (--·) wild type SNase in 6 M GuHCl.