Protein extraction and solubilization of KDP and WHEY
Dried dietary protein powder (10 mg) of KDP and WHEY were extracted overnight by rotation (Mini Labroller, Labnet International Inc) at room temperature in 1 ml of extraction buffer (8 mM urea, 0.05 M Tris, 50 mM TCEP, pH 4). Extracted protein was spun down at 3000 g for 5 min and the absorbance of the supernatant was measured at 280 nm (Nano photometer, Implen) against the appropriate blank after dilution (1:10). The protein solutions were kept at 4 °C until assessment of thiol groups.