Peptide mapping of ASC and PSC was performed according to the
method of Kittiphattanabawon et al. (2005) with slight modification.
A collagen sample (6 mg) was dissolved in 1 ml of 0.1 M sodium
phosphate, pH 7.2 containing 0.5% (w/v) SDS, the mixture
preheated at 45°C for 3 h and 300 µl of the preparation transferred
to test tubes for digestion. To initiate the digestion, 20 µl of lysyl
endopeptidase from Achromobacter lyticus, (5.0 µg/ml) was added
to the mixture, which was then incubated at 37°C for 5 min.
Proteolysis was stopped by boiling for 3 min. SDS-PAGE was
performed by the method of Laemmli (1970) in 10% acrylamide
NuPAGE Bis-Tris Mini Gels with MOPS buffer, followed by staining
and destaining as previously described.