The correlation between the aggregate state (monomers, associates), rheological properties and the secondary structure of the native and recombinant beta-caseins was studied by the complex of biophysical methods (fluorescence, CD and IR spectroscopy, dynamic light scattering). The experimental data on the mechanisms of beta-casein self-association that specifies its colloidal state limits was obtained, the temperature of monomer-micelle transitions, the size of aggregates of protein native and modified forms were determined. Micelle-forming ability and micellar solubilization capacity of beta-casein micelles towards hydrophobic vitamin retinol were characterized. The effect of the low ionic strength of the solution on the binding and thermodynamic stability of beta-casein complexes with a hydrophobic ligand was analyzed. The resulting binding constants confirm that the binding in retinol-beta-casein complexes depends on the conformation of the protein molecule and the ionic strength of the solution. The obtained insights on the mechanisms of conformational transitions, self-association, interaction of beta-casein with target ligands at the molecular level, contribute to the design and development of effective protein carriers of bioactive additives and drugs.
beta-casein, micelle, self-association, critical micelle concentration (CMC), binding constant
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