Casein electrophoretic separation

Electrophoretic Methods. Several electrophoretic procedures have been developed to fractionate or purify the various caseins (McKenzie 1971C Thompson 1971 Whitney 1977). Wake and Baldwin (1961) fractionated whole casein by zone electrophoresis on cellulose powder in 7 M urea and 0.02 ionic strength sodium phosphate buffer at pH 7 and 5°C. Payens and co-workers employed several somewhat different electrophoretic conditions for the fractionation and purification of the caseins on cellulose columns (Payens 1961 Schmidt and Payens 1963 Schmidt 1967). Three fractions, as-, k-, and /3-caseins, were separated at pH 7.5 and 30°C with 4.6 M urea-barbiturate buffer. The purification of asi-casein and the separation of the genetic variants of K-casein were accomplished by altering the electrophoretic conditions. Manson (1965) fractionated acid casein on a starch gel column stabilized by a density gradient at 25 °C. 

The combined electrophoresis-TLC procedure has proved very satisfactory [299, 342, 692]. The order in which the operations is carried out is immaterial in principle and will be dictated by the circumstances. It is important here also, however, that solvent and electrolyte be completely removed after the first run. If, therefore, salt-containing buffers are to be used for the electrophoresis, the chromatography stage must be the first. The plate for the subsequent electrophoretic separation must however be sprayed most cautiously so as not to wash away the substances already separated. The separation of a casein hydrolysate is shown in Fig. 59. 

Normally, Jf-casein occurs as a trimer or as a higher oligomer in which the formation of disulfide bonds is probably involved. The protein contains varying amounts of carbohydrates (average values 1% galactose, 1.2% galactosamine, 2.4% N-acetyl neuramic acid) that are bound to the peptide chain through Thr-131, 133, 135 or (in variant A) 136. Jf-Casein is separated electrophoretically into various components that... 

Casein is a naturally occurring macromolecule that accounts for approximately 80% of the protein content of cow s milk it is a phosphoprotein that can be separated into various electrophoretic fractions, such as aj-casein, /c-casein, fi-casein, and y-casein in which each constituent differs in primary, secondary, and tertiary structure, amino acid composition, and molecular weight (Ghosh et al., 2009 Audic et al., 2003 Barreto et ai., 2003]. It finds use in making adhesives and paper coatings. 

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