Preparation of κ-Casein by Gel Filtration

A procedure for the preparation of pure κ-casein by Sephadex gel filtration is described. Unreduced casein is filtered through a 2.5- by 95-cm column of Sephadex G-150 equilibrated with 0.005m triscitrate buffer, pH 8.6, containing 6 m urea. κ-Casein is excluded from the gel and emerges as a sharp peak at the void volume; all other caseins are retarded by the gel. The method is particularly suitable for preparing pure κ-casein in good yield from small quantities of whole casein, but larger amounts of κ-casein are readily prepared. The method is also suitable for the purification of κ-casein-rich preparations.