Differences between CNBr peptides of soluble and insoluble bovine collagens

The compositions of the cyanogen bromide peptides of insoluble bovine skin and dentin collagens are nearly identical with those obtained from the soluble collagen. However, some qualitative and quantitative differences are present. The insoluble collagens do not go completely in solution after the treatment. The insoluble residues have compositions showing a firm association of collagen with non-collagenous peptides. The content of peptide α1-CB6 is sharply reduced in both insoluble skin and dentin collagen, indicating involvement of this peptide in the formation of intermolecular cross-links. Several heterogeneities were noted regarding many peptides. In particular, two forms of α1-CB3 and of α1-CB6 were isolated in agreement with the idea that two types of α1-chains are present. The situation is more complex, in that the second form of α1-CB3 from skin and dentin are not identical.