Ovalbumin, Ovotransferrin, Lysozyme: Three Model Proteins for Structural Modifications at the Air−Water Interface

Structural modifications of ovalbumin, ovotransferrin, and lysozyme at the air−water interface have been investigated using SDS-PAGE, both intrinsic and ANS fluorometry, and circular dichroism experiments. Ovalbumin contact with an interface induced an exposure of aromatic residues, a slight decrease in α-helix structures (−1.7%), and an increase in both β-sheet (+3.4%) and β-turn (+7.9%) structures. Moreover, these conformational changes led to the formation of insoluble polymers of ovalbumin through intermolecular disulfide bonds. Ovotransferrin contact with an interface led to an increase in its surface hydrophobicity (+30%) and modifications of its secondary structure (−33% of α-helices, +96.4% of β-sheets, +13.2% of β-turns, and +21.2% of random coils), characteristic of major conformational changes. On the other hand, lysozyme did not undergo any structural modification. These results clearly underscore that at the air−water interface proteins are susceptible to denaturation. Keywords: Ovalbumin; ovotransferrin; lysozyme; air−water interface; structure