The association of bovine SH-kappa-casein at pH 7.0.

The self-association of SH-kappa-casein at pH 7.0 in 0.01 M-EDTA, 0.001 M-dithiothreitol buffer, containing 0.1, 0.2, 0.5 or 1.0 M-NaCl is of a monomer-polymer type. The polymer is a spherical particle, diam. 23 nm and mol. wt 570000 (30 monomers). These parameters are not greatly influenced by variations in ionic strength above 0.1. The critical micelle concentration, which is a property of a monomer--polymer equilibrium, decreases with increasing ionic strength. The standard free energy of association is about -36 kJ/mol. monomer at 20 degrees C.