Multidimensional evaluation of structural properties of ovalbumin at the air-water interface: Spectroscopy and molecular dynamics simulations

The structural transitions and molecular properties of the most abundant ovalbumin in eggs at the air-water (foam) interface were investigated by spectroscopic and molecular dynamics (MD) simulation techniques. The results of UV-Vis, second-derivative and CD spectra demonstrated that the alkaline environment and the airwater interface promoted the structural stretching of ovalbumin and the increase of polarity especially for tryptophan. The higher zeta potential detected in foam and high pH conditions meant that electrostatic repulsion due to negative surface charges provided the driving force for the unfolding of ovalbumin. Moreover, MD analysis illustrated that the second half of the ovalbumin structure possessed more complex interactions and that non-hydrogen bonding forces played an essential role in protein migration. Both the protein skeleton and protein-water interactions were strongly disturbed by the air-water interface. Amino acids at positions 110, 136, 168 and 318 might be critical in the structural rearrangement. This work would provide new insights into protein interface properties and provide theoretical support for the targeted regulation of egg white foam capacity and stability.