Structural and functional changes of bovine beta-lactoglobulin - a food allergen - after adsorption on hydrophobic surfaces

Adsorption of protein molecules on interfaces occurs in natural and man-made systems, and plays a central role in many events related to human health, to food science, and to environmental issues. Structural rearrangements upon contact with the sorbent phase may affect the protein's biological activities (allergenicity, bioavailability, ability to bind micro- and macromolecular ligands). Structural and functional changes that bovine beta-lactoglobulin (BLG) - a relevant food allergen - undergoes upon adsorption on hydrophobic surfaces (polystyrene nanoparticles or oil-in-water microemulsions) were evaluated by means of intrinsic fluorescence spectroscopy, binding of fluorescent probes, accessibility of cysteine thiols, and limited proteolysis. Changes in immunoreactivity were evaluated by competitive ELISA using epitope-specific monoclonal antibodies. Our results indicate that BLG undergoes an extended stretch of the native structure after adsorption on hydrophobic surfaces, exposing regions buried from the aqueous media in the native structure. As a result, both the proteolytic resistance and the immunoreactivity of BLG are markedly altered upon absorption.