Purification and some physicochemical properties of bovine kappa-casein.
1. A description is given of the fractionation of kappa-casein on DEAE-cellulose using a pH gradient. With this method an improved separation of the kappa-casein components with a higher negative charge is obtained. 2. It is shown that at least one of the kappa-casein fractions has a second phosphate ester group. The heterogeneity of kappa-casein therefore is not exclusively caused by a varying N-acetylneuraminic acid content. 3. Ultracentrifuge experiments and exclusion gel chromatography show that the purified kappa-casein fraction having the lowest electrophoretic mobility exhibits a monomer-polymer association equilibrium. The free energy of association per mol monomer in 0.2 M NaCl is approximately --36 kJ-mol-1.
D000818:Animals; D002364:Caseins / Q000302:isolation & purification; D002417:Cattle; D004592:Electrophoresis, Starch Gel; D005260:Female; D006720:Homozygote; D008892:Milk; D008970:Molecular Weight; D009943:Organophosphorus Compounds / Q000032:analysis; D012794:Sialic Acids / Q000032:analysis
D002364:Caseins; D009943:Organophosphorus Compounds; D012794:Sialic Acids