The anomalous behavior of collagen peptides on sodium dodecyl sulfate-polyacrylamide gel electrophoresis is due to the low content of hydrophobic amino acid residues.

The anomalously low mobility of collagen peptides on SDS-gel electrophoresis was investigated, using tadpole skin collagen and bovine Type I, II, and III collagens. The free electrophoretic mobility of alpha 1 chains of collagen was found to be smaller than those of alpha 2 chain and common proteins of similar size, which migrate on SDS-gel according to their molecular weights. The retardation coefficient of collagen peptides was normal. Therefore, the overall SDS-collagen complex may be comparable in size with SDS complexes of common proteins with similar molecular weights. One characteristic difference of collagen in comparison with common proteins is its low content of hydrophobic amino acid residues. This may account for the low free electrophoretic mobility in SDS of collagen alpha 1 chains, if the SDS-protein complex is of a necklace type, not a rod-like type.