Mg/ml gelatin as a protease substrate. Following electrophoresis, gels were placed in 2.7 Triton X-100 for 30 min to remove SDS, and then incubated with developing buffer (50 mM Tris base, 40 mM HCl, 200 mM NaCl, 5 mM CaCl2, and 0.2 Briji 35; Novex) at 37 for 24 h on a rotary shaker. After incubation, gels were stained in 30 methanol, 10 acetic acid, and 0.5 w/v Coomassie brilliant blue for