The protein ladder (PageRuler Plus, Thermo
Scientific) was also loaded in the first well of each gel. The electrophoresis
was carried out in Tris–HCl buffer (pH 8) with SDS at
80 mA for 2 h. After electrophoresis, the gels were stained with
Coomassie brilliant blue (R-250, Sigma–Aldrich, Oakville, ON)
overnight and then de-stained in a methanol/acetic acid/water
solution (40:7:53 v/v/v) for 4 h.