Preparation of ³H-labeled serum glycoproteins from antarctic fish

Radioactive glycoproteins were prepared from the purified serum glycoproteins of antarctic fish by introducing tritium atoms (³H) into their carbohydrate moiety. The carbohydrate moiety is composed of disaccharides, β-D-galactosyl-(1→4) α-N-acetylgalactosamine, which accounts for 60% of the molecule. The hydroxyl groups (OH) at the carbon-6 positions of both sugar residues were oxidized with galactose oxidase to aldehyde groups and subsequently reduced to hydroxyl groups (O³H) with sodium borohydride-³H (NaB³H₄). Under suitable conditions, the end products (tritiated glycoproteins) are highly radioactive and retain their original unique freezing point depressing activity.