PHOSPHORYLATION OF BETA-LACTOGLOBULIN UNDER MILD CONDITIONS

beta-Lactoglobulin was phosphorylated with different molar ratios of POCl3/protein (20, 40, and 80) in the presence of either triethylamine or hexylamine (6 mol of base/mol of POCl3) in aqueous conditions. Urea-PAGE, SDS-PAGE, and isofocusing patterns showed increasing negative charges and little cross-linking on beta-lactoglobulin molecule. The circular dichroism spectra showed that phosphorylation has disordered the secondary structure of beta-lactoglobulin. The phosphorylation-induced structural and electrostatic changes have displaced modified beta-lactoglobulin solubility minima toward lower values.