Interaction of B-casein at an emulsion interface studied by ²H NMR and molecular modeling (2001)
- Autor USP: AREAS, JOSE ALFREDO GOMES - FSP
- Unidade: FSP
- Subjects: PROTEÍNAS; LIPÍDEOS
- Language: Inglês
- Abstract: Interactions between B-casein at a lipid/water interface were studied by solid-state ²H NMR using neutral and charged liposomes. The bilayers were composed of dimyristoylphosphatidylcholine with the four hydrogen at A- and B- positions (DMPC-d4), and the nine protons at the Y-position (DMPC-d9), substituted by deuterium, as single component or as mixed bilayers with dimyristoylphosphatidyl-glycerol (DMPG) in a molar ratio, 1:1. Structural characteristics of B-casein were studied by molecular modeling using techniques that permit modeling of the dynamics of proteins in solvents and in water/lipid interfacial regions. It was showm previously that B-casein was able to interact both with the charged and non-charged interface. In this work we observed changes in the ²H NMR qradupole splittings as protein concentration increased from a lipid/protein molar ratio of oo (pure lipid) to 5,000:1. The interaction with the charged liposomes showed an electrostatic behavior with a remarkable effect when the lipid/protein ratio approached 30,000:1. The line shape of the spectra near this concentration changed dramatically reducing the quadrupole splitting from 1,000 to 300 Hz. the interaction with non charged liposomes showed fast two-site exchange kinetics, as tested with equations described previously, between the protein-free part of the bilayer and the protein-associated phase when protein was at low concentration, changing to a distinct type of interaction thereafter whenlipid/protein ratio reached 12,000:1. Molecular modeling from a proposed distented three-dimensional structure for B-casein showed that, after optimization and thermalization, the molecule evolved to a folded structure in the water milieu and had this folding further increased when in presence of a lipid interface. This compact structure remained oriented in a lipid/water interface and proved to be flexible and able to keep spatial separation between charged phosphoserine residues and hydrophobic amino acids. Although different from the accepted distended structure, this more compact configuration reproduced the experimentally observed amphiphilic behavior of B-casein at a water/lipid interface and could account for the typical mass/area ratio observed for B-casein emulsions
- Título do periódico: Magnetic resonance in food science: a view to the future
ABNTAREAS, José Alfredo Gomes; CASSIANO, M. M.; GLAUBITZ, C.; GRÖBNER, G.; WATTS, A. Interaction of B-casein at an emulsion interface studied by ²H NMR and molecular modeling. In: Magnetic resonance in food science: a view to the future[S.l: s.n.], 2001.
APAAreas, J. A. G., Cassiano, M. M., Glaubitz, C., Gröbner, G., & Watts, A. (2001). Interaction of B-casein at an emulsion interface studied by ²H NMR and molecular modeling. In Magnetic resonance in food science: a view to the future. Cambridge: Royal Society of Chemistry.
NLMAreas JAG, Cassiano MM, Glaubitz C, Gröbner G, Watts A. Interaction of B-casein at an emulsion interface studied by ²H NMR and molecular modeling. In: Magnetic resonance in food science: a view to the future. Cambridge: Royal Society of Chemistry; 2001.
VancouverAreas JAG, Cassiano MM, Glaubitz C, Gröbner G, Watts A. Interaction of B-casein at an emulsion interface studied by ²H NMR and molecular modeling. In: Magnetic resonance in food science: a view to the future. Cambridge: Royal Society of Chemistry; 2001.
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