4.2.2. Sodium Dodecyl Sulfate Polyacrylamide-Gel Electrophoresis (SDS-PAGE)

SDS-PAGE was performed, following the method of [45] with slight modifications, using 7.5% separating and 5% stacking gel. The collagen samples were dissolved in the sample buffer and the obtained mixture (1 mg/mL) was heated at 100 °C for 5 min. The mixture was centrifuged at 4000 rpm for 5 min using a microcentrifuge at room temperature to remove debris. A total of 20 μg of the sample was loaded onto a polyacrylamide gel and subjected to electrophoresis at a constant voltage (100 V) for 1 h using MiniProtein II unit (Bio-Rad Laboratories, Inc. Richmond, CA, USA). The resultant gel was stained with 0.1% (w/v) Coomassie blue R-250 in 50% (v/v) methanol and 10% (v/v) acetic acid for 2 h and destained with 40% (v/v) methanol and 10% (v/v) acetic acid. High molecular weight markers were loaded alongside the collagen to estimate the molecular weight of MC, and commercial atelocollagen (Atelocollagen, Dalim Tissen, Korea) was loaded next to the protein marker as standard collagen.