Binding mechanisms between lycopene extracted from tomato peels and bovine β-lactoglobulin

Fluorescence spectroscopy and computational methods were used to study the interaction mechanism between lycopene extracted from tomato peels and bovine beta-lactoglobulin (beta-LG). The chromatographic analysis of the extract allowed identification and quantification of nineteen carotenoids, with lycopene representing approximately 72% from the total carotenoids in the extract. The beta-LG fluorescence has been regularly quenched upon increasing the lycopene concentration, suggesting the formation of the complex, whereas a dynamic quenching process was highlighted. The thermodynamic parameters suggested that the interactions between the protein and ligand are driven by van der Waals' force and hydrogen bonding. Molecular docking was employed to find out details on lycopene binding to the beta-LG molecule equilibrated by means of molecular dynamics at different temperatures. The key interactions assuring beta-LG - lycopene complex formation varied with the temperature. When the protein was heated at mild temperatures, the lycopene was found to bind on top of the calyx, whereas due to the conformational changes enabled by the thermal treatment at 90 degrees C, the most favorable ligand binding site involved amino acids responsible for stabilizing the dimmer.