Study of the Interaction of Quercetin and Taxifolin with β-Lactoglobulin by Fluorescence Spectroscopy and Molecular Dynamics Simulation

The interaction between quercetin and taxifolin with β-lactoglobulin (BLG) was investigated via various methods, including fluorescence spectroscopy, molecular docking and molecular dynamics (MD) simulation. The results have demonstrated that quercetin binds BLG with an affinity higher than that of taxifolin, which is attributed to the nonplanar C-ring and steric hindrance effect in taxifolin. The synchronous fluorescence spectra shows that quercetin and taxifolin do not induce conformational changes of BLG. Molecular docking studies have demonstrated that several amino acids are involved in stabilizing the interaction. Analysis of the MD simulation trajectories shows that the root mean square deviation (RMSD) of various systems reaches equilibrium. Time evolution of the radius of gyration shows as well that BLG and BLG-flavonoid complexes are stable within 5 ns. In addition, analyzing the RMS fluctuations, one can suggest that the structure of the ligand binding site remains rigid during the simulation. The secondary structure of BLG is preserved upon interaction with these flavonoids.