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 investi-gated, using tadpole skin collagen and bovine Type I, II, and HI collagens. The free electrophoretic mobility of cti chains of collagen was found to be smaller than those of a, 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 ax chains, if the SDS-protein complex is of a necklace type, not a rod-like type. SDS-polyacrylamide gel electrophoresis is now widely used for the separation and characterization of many proteins (J). Most proteins migrate on SDS-gel according to their molecular weights, but some proteins do not. Collagen peptides are among these "anomalous " proteins. Furthmayr and Timpl (2) suggested that collagen peptides might have a more rigid conformation in SDS (due to the high content of imino acid residues) than common proteins which migrate on SDS-gel according to their molecular weights. It was shown that succinylated collagen, which presum-ably carries more negative charge than the un