Isoelectric fractionation of sulfated glycoproteins on polytetrafluoroethylene-coated columns

The isolation of the acidic glycoproteins in mucous secretions is impeded by their low solubility and high viscosity in aqueous media. Mucin preparations have therefore been treated with alkali (1), detergents or reducing agents (2), boiling (3) or proteolytic enzymes (4,5) prior to conventional fractionation procedures. However, such agents may irreversibly alter the protein structure (1–5). In the present paper a fractionation method based on isoelectric focusing, and without sample pretreatment, is described.