Two-Dimensional Electrophoresis of Bovine Milk Proteins

A two-dimensional electrophoretic technique for the analysis of bovine milk proteins was developed.The first dimension separation was by isoetectric focusing in the presence of a nonionic detergent (Nonidet NP-40) and urea and utilized a modified pH gradient from pH 3 to 10. Isoelectric separation was followed by discontinuous, dissociating PAGE using a 14% acrylamide concentration for the resolving gel.This procedure is able to separate the major bovine milk caseins into classes, and to resolve at least some of the genetic variants of these classes.~3-Lactoglobulin was also resolved into two bands differing in isoelectric point.The technique was used to examine the effects of high speed centrifugation on the distribution of casein proteins in raw skim milk.