Structural Changes of Interfacial Proteins in Emulsions Evaluated by Molecular Dynamics Combined with Raman Spectroscopy

Abstract

In this study, 1.5% (m/m) tilapia myofibrillar protein (MP) and corn oil (0%, 10%, 68% or 70%, V/V) were used to prepare emulsions. Molecular dynamics (MD) combined with Raman spectroscopy was used to investigate the structural changes of MP adsorbed at the emulsion interface. MD simulation showed that the spatial conformation of myosin was changed when the protein adsorbed onto the interface of emulsions with different proportions of oil phase; the secondary structure contained about 48% α-helix, and the structure remained relatively stable after the protein adsorbed onto the interface. The change of myosin spatial conformation was accompanied by the increase of solvent accessible surface area (SASA) and the enhancement of hydrophobic interaction, which made the emulsion stable. Raman spectra showed secondary structural changes similar to those of MD. In addition, Raman spectroscopy results showed that tryptophan (Trp) and tyrosine (Tyr) residues were exposed on the protein surface and participated in hydrogen bond formation and hydrophobic interaction, which was conducive to the stability of the emulsion system. In conclusion, changes in the spatial conformation and the microenvironment of side chain groups of MP adsorbed at the oil/water interface of emulsions can promote the hydrogen bond and hydrophobic interaction between protein molecules, and consequently the formation of a tight interfacial film at the oil/water interface, which is conducive to improving the stability of emulsions.

Keywords

• emulsion; interfacial protein; molecular dynamics; raman spectroscopy