In vitro evidence on protease resistance of glycated protein. BSA was glycated and ribosylated with glucose and ribose respectively, which showed protease resistance to tryptic digestion. Lane 2, 3, and 4 contains undigested BSA, Gly-BSA, and Rib-BSA respectively, whereas lane 5, 6, and 7 contains the same digested with trypsin, Try-BSA, Try-Gly-BSA, and Try-Rib-BSA respectively, and Lane 1 contains SDS-PAGE marker. The experiment was repeated independently three times.