Comparative study of the interaction between β-lactoglobulin and three carotenoids

Area of Science:

• Food Science
• Biochemistry
• Molecular Nutrition

Background:

• Carotenoids are vital nutrients with significant health benefits.
• Beta-lactoglobulin (β-lg) is a primary protein in milk, known for its ligand-binding capabilities.
• Understanding protein-carotenoid interactions is crucial for food fortification and bioavailability.

Purpose of the Study:

• To investigate the binding interactions between beta-lactoglobulin (β-lg) and three distinct carotenoids: lycopene (LYC), β-carotene (β-CA), and lutein (LU).
• To elucidate the molecular mechanisms governing these interactions, including binding forces and conformational changes.
• To assess the impact of carotenoid binding on β-lg's physicochemical properties.

Main Methods:

• Fluorescence spectroscopy was employed to study the quenching mechanism and binding affinity.
• Thermodynamic parameters (e.g., Gibbs free energy) were calculated to determine binding spontaneity.
• Spectroscopic techniques and molecular dynamics simulations were used to analyze conformational changes.
• Particle size and zeta potential measurements assessed alterations in protein aggregation and stability.

Main Results:

• A static quenching mechanism indicated spontaneous binding (ΔG < 0) between β-lg and all tested carotenoids.
• Lutein (LU) exhibited the strongest binding affinity with β-lg compared to lycopene (LYC) and β-carotene (β-CA).
• Carotenoid binding induced conformational alterations in β-lg, reduced surface hydrophobicity, and increased particle size and zeta potential in a concentration-dependent manner.
• Molecular dynamics simulations corroborated the spectroscopic findings, confirming structural changes in the β-lg-carotenoid complexes.

Conclusions:

• The study provides a detailed molecular understanding of carotenoid-β-lg interactions, highlighting differential binding affinities and mechanisms.
• Lutein demonstrates superior binding to β-lg, involving hydrophobic, van der Waals forces, and hydrogen bonds.
• Carotenoid binding significantly modifies β-lg's structure and properties, offering insights for nutritional applications.