A Comparison of Some of the Chemical and Physical Properties of γ-Casein and Immune Globulins of Milk

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Abstract
To identify the slowest component in the electrophoretic pattern of skimmilk at pH 8.7 and to further investigate the chemical and physical properties of gamma-casein and the immune globulins, these proteins were isolated from milk and colostrum. Phosphorus analyses indicate a distinct difference between gamma-casein and immune globulins. In veronal buffer at pH 8.7 [image]/2 = 0.1, the electrophoretic mobilities of gamma-casein and pseudoglobulin are the same. In glycine hydrochloride buffer pH 2.3, [image]/2 = 0.1, the 3 proteins have different electrophoretic mobilities but a mixture of gamma-casein-euglobulin interacts, the extent depending on the time of storage at 4[degree]C. While gamma-casein is electrophoretically homogeneous in glycine hydrochloride buffer at pH 2.3 and 3.25 and [image]/2 = 0.1, it is heterogeneous in comparable sodium lactate buffers, due to interactions with the lactate ion. All 3 proteins contribute to the area of the slowest moving component in the electrophoretic pattern of skimmilk at pH 8.7. They are heterogeneous in the ultracentrifuge. The molecular weight calculated for the major component of gamma-casein varied with pH while the frictional ratios were the same in veronal and glycine hydrochloride buffers but decreased in sodium lactate buffer. Molecular weights of euglobulin and pseudoglobulin were not pH dependent, but their frictional ratios increased with decreasing pH values.

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