Nuclear magnetic resonance study of the conformation and dynamics of beta-casein at the oil/water interface in emulsions

A (13)C and (31)P nuclear magnetic resonance (NMR) study has been carried out on beta-casein adsorbed at the interface of a tetradecane/water emulsion. (13)C NMR spectra show signals from the carbonyl, carboxyl, aromatic, and C alpha carbons in beta-casein, well resolved from solvent resonances. Onl...

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Bibliographic Details
Published in:Biophysical journal 1996-05, Vol.70 (5), p.2396-2402
Main Authors: ter Beek, L.C., Ketelaars, M., McCain, D.C., Smulders, P.E., Walstra, P., Hemminga, M.A.
Format: Article
Language:English
Subjects:
ADSORCION
ADSORPTION
AGUA
ALKANES
Animals
CARBON
Carbon Isotopes
CARBONE
CARBONO
CASEIN
CASEINA
CASEINE
Caseins - chemistry
Cattle
EAU
EMULSION
EMULSIONS
ESPECTROSCOPIA RMN
FOSFORO
HIDROCARBUROS
HYDROCARBONS
HYDROCARBURE
INTERFACE
INTERFACE PHENOMENA
ISOTOPE RADIOACTIF
Magnetic Resonance Spectroscopy - methods
MOLECULAR CONFORMATION
NMR SPECTROSCOPY
Oils
PHENOMENE D'INTERFACE
PHOSPHORE
PHOSPHORUS
Phosphoserine - analysis
Protein Conformation
RADIOISOTOPES
RADIOISOTOPOS
SPECTROSCOPIE RMN
STABLE ISOTOPES
STRUCTURE
TETRADECANE
WATER
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Description
Summary:A (13)C and (31)P nuclear magnetic resonance (NMR) study has been carried out on beta-casein adsorbed at the interface of a tetradecane/water emulsion. (13)C NMR spectra show signals from the carbonyl, carboxyl, aromatic, and C alpha carbons in beta-casein, well resolved from solvent resonances. Only a small fraction of all carbon atoms in beta-casein contribute to detectable signals; intensity measurements show that the observable spectrum is derived from about 30 to 40 amino acid residues.(31)P 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 alpha-carbon region, indicates that a large part of the protein is in a random coil conformation with restricted motion and a relatively long internal correlation time. The NMR results show that the conformation and dynamics of the N-terminal part of beta-casein are not strongly altered at the oil/water interface, as compared to beta-casein in micelle-like aggregates in aqueous solution.
ISSN:0006-3495
1542-0086
DOI:10.1016/S0006-3495(96)79807-7