Some physicochemical properties of bovine alpha s 2-casein.

The self-association of purified bovine alpha s 2-casein in 0.005 M EDTA, pH 6.7, at ionic strengths varying from 0.02 to 1.2 depends strongly on the ionic strength. The association reaches its maximum at an ionic strength (I) between 0.02 and 0.3 and can be described by the so-called isodesmic model. The standard free energy of association is about -38 kJ/mol at 20 degrees C. If it is assumed that the particles are spherical and have a voluminosity which is independent of the degree of association, then from the intrinsic viscosities at different ionic strengths the radius of the spherical particle (approximately equal to 3.7 nm), the voluminosity (approximately equal to 5 ml . g-1) and the solvation (approximately equal to 4.2. g . g-1) can be obtained.