Fig. 3. Bis-alkylated peptides are reducible and more resistant to proteolysis. (A) Dealkylation of model peptides 1c, 1d, and 1i (1 mmol) in the presence of PyS (10 mmol) in PBS (pH = 7.4) at 37 °C. HPLC traces of dealkylation process of peptide 1c at different time intervals were presented. (B) Plot of regenerated peptides versus time. (C) In vitro trypsin (1%) digestion assay. Peptide 1, 1c, and 1i (1 mmol) incubated at 37 °C for different time intervals. The amounts of the peptides were examined by integration of reverse-phase HPLC.