Gel Filtration of Acid Casein and Skimmilk on Sephadex

Abstract

Sodium caseinate solutions were fractionated by Sephadex G-200 columns at pH 8.0, 4[degree]C. The casein components of the chromatographic fractions were identified by starch gel electrophoresis. When 0.02 M_ phosphate buffer containing 1M_ NaCl was used as elutant, the casein was resolved into 3 main fractions. The first 2 were aggregates of [kappa]-, [alpha]s- and [beta]-casein, probably in a form of complex. The 3rd fraction was essentially [beta]-casein present as the monomer. When urea was included in the eluting buffer and pH raised from 8.0 to 8.6 the complexes of [alpha]s - [beta]-casein were dissociated into smaller units, probably monomers. Relatively pure [kappa]-casein was obtained in the void vol. by using G-100 at pH 8.5. When skim milk was passed through column of Sephadex G-200 at 4[degree]C and phosphate buffer of pH 7.0 was used as elutant, the Sephadex acted as an effective dialyzer, removing inorganic Ca and P from the caseinate micelles with resulting micellar disintegration.