Publication Date

10-1992

Abstract

A preparative isoelectric focusing (IEF) method was applied to separate skim milk proteins using the Rotofor device in a pH 3-10 gradient containing 4 M urea/1% triton X-100. Each of the 20 fractions obtained from the Rotofor device was then analyzed by polyacrylamide gel electrophoresis (PAGE). Both urea-PAGE and SDS-PAGE were used to separate purified caseins and skim milk resulting in comparable two-dimensional pattern. The major bovine caseins (αs1, αs2, β, κ-casein) were resolved better on urea-PAGE. The αs1- and β -casein were focused at pH ~ 4.5 and 4.8, respectively, whereas αs2-caseins focused as several bands at pH 6.2- 6.8. The A variant of κ -casein focuses at Fractions 6 9 which is slightly more acidic than the B variant that focuses at Fractions 7-13. No sample pretreatment was necessary to analyze skim milk proteins and urea-PAGE clearly resolved bans of all major caseins and whey proteins. Preparative isoelectric focusing followed by PAGE was found to be a useful and powerful method to analyze milk proteins in two-dimensions. This technique facilitates the analysis of the relative amounts of proteins in milk, as well as simplifies the detection of changes and foreign proteins in milk.

Disciplines

Dairy Science

Included in

Dairy Science Commons

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URL: http://digitalcommons.calpoly.edu/dsci_fac/59