Self-assembly and secondary structure of beta-casein

The secondary structure alterations during isothermal and temperature guided beta-casein micellization were studied by dynamic light scattering, circular dichroism and Fourier transform infrared spectroscopy techniques. Micelle formation induced by the increase in the protein concentration at constant temperature is accompanied by the formation of a small number of additional peptide hydrogen bonds, preliminary assigned to the intraprotein beta-structure. The heating results in more pronounced but qualitatively different changes consisted in dehydration of the peptide groups and disruption of the polyproline II helix segments with the subsequent conversion to the random conformation and the beta-turns. Nevertheless, in both cases the total number of residues involved in the transition is very few and cannot be regarded as a decisive factor for casein micellization.