NUCLEAR-MAGNETIC-RESONANCE STUDY OF THE CONFORMATION AND DYNAMICS OF BETA-CASEIN AT THE OIL WATER INTERFACE IN EMULSIONS/

A(13)C and P-31 nuclear magnetic resonance (NMR) study has been carrie d out on beta-casein adsorbed at the interface of a tetradecane/water emulsion, C-13 NMR spectra show signals from the carbonyl, carboxyl, a romatic, and C-alpha carbons in beta-casein, well resolved from solven t resonances, Only a small fraction of all carbon atoms in beta-casein contribute to detectable signals; intensity measurements show that th e observable spectrum is derived from about 30 to 40 amino acid residu es, P-31 NMR spectra show signals from the five phosphoserines on the hydrophilic N-terminal part of the protein, Analysis of T-1 relaxation times of these nuclei, using the model free approach for the spectral density function and the line shape of the cu-carbon region, indicate s that a large part of the protein is in a random coil conformation wi th restricted motion and a relatively long internal correlation time. The NMR results show that the conformation and dynamics of the N-termi nal part of beta-casein are not strongly altered at the oil/water inte rface, as compared to beta-casein in micelle-like aggregates in aqueou s solution.