Fig. 2. (A) The calibration curve for Superose-12 column with bovine serum albumin, ovalbumin, chymotrypsinogen, ribonuclease A. The curve was obtained as described in the text. Protein concentration is 0.2 mg/ml. (B) The Stokes radii of the F34W/W140F mutant and the wild type SNase at different protein concentrations. (solid square) the F34W/W140F mutant; (solid circle) the wild type SNase. All chromatography was carried out in 30 mM Tris-HCl, pH 7.4, at a flow-rate of 0.4 ml/min at 25°C. The effluent was monitored at 280 nm.