title: Isoelectric focusing of heparin. Evidence for complexing with carrier ampholytes.
abstract: The basis for heparin fractionation into 21 components by isoelectric focusing has been shown to be a strong interaction between the polysaccharide and different amphoteric species in the Ampholine mixture. This was demonstrated by altering the heparin/Ampholine ratio, by loading the sample either before focusing or to a prefocused gel slab and by re-running single heparin bands. The complexes exhibiting apparent pI values in the pH range 3.2--4.5 appear to be particularly stable, probably because an optimal amount of amino groups (4 to 5) in the Ampholine molecules are protonated. When stained with Toluidine blue, the heparin/Ampholine complexes precipitated in the gel exhibited different degrees of metachromasia, reflecting competition of the dye and individual components of Ampholine with respect to binding sites of heparin: at least three colours, violet, blue and indigo, are distinguishable. Ampholine, when added to a heparin . Toluidine blue complex in solution displaces the dye from the polysaccharide.
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D006493:Heparin / Q000302:isolation & purification; D007525:Isoelectric Focusing; D007700:Kinetics; D013053:Spectrophotometry; D013552:Swine; D014048:Tolonium Chloride
chemical_list: D014048:Tolonium Chloride; D006493:Heparin