2.4. SDS–polyacrylamide gel electrophoresis (SDS–PAGE)
SDS–PAGE was performed following the method of Laemmli
[34] with slight modifications, using 7.5% separating and 5% stacking
gel. Collagen sample was dissolved in sample buffer and
obtained mixture (1.5 mg/1 ml) was heated at 95 ◦C for 5 min. The
mixture was centrifuged at 4000 rpm for 5 min using micro centrifuge
at room temperature to remove debits. 10 g of sample was
loaded on to polyacrylamide gel and subjected to electrophoresis
at a constant current (15 mA/gel) for 1 h and 30 min using Mini
Protein II unit (Bio-Rad Laboratories, Inc., Richmond, CA, USA).
Resultant gel was stained with 0.05% (w/v) Coomassie blue R-
250 in 15% (v/v) methanol and 5% (v/v) acetic acid for 4 h and
destained with 30% (v/v) methanol and 10% (v/v) acetic acid.
High MW markers were loaded alongside the collagen to estimate
the molecular weight of collagen and porcine skin type
I collagen was loaded next to protein marker as a standard
collagen.