Two-dimensional electrophoretic analysis of human milk-fat-globule membrane proteins with attention to apolipoprotein E patterns

Two-dimensional (2-D; Iso Dalt method) electrophoresis was done on lipid membrane fractions from human milk samples collected in polypropylene tubes at home by the mother. The samples represent milk from two weeks to ten months post partum. Identification was made by immunoassay of Western blots. Apolipoprotein E was not easily seen on silver-stained gels because concentration is small and spots overlap another protein. Blot assays show a more complex pattern than 34 kDa plasma apo E with molecular size isoforms at 36 kDa, 34 kDa, 20 kDa and 15 kDa. One sample was negative for apo E. Apo E plays an important role in lipid transport in tissue and in the brain. It is synthesized in a variety of tissues by specific cells. Milk may reflect several sources.