Molecular insight into binding behavior of polyphenol (rutin) with beta lactoglobulin: Spectroscopic, molecular docking and MD simulation studies

The interaction of natural polyphenolic compounds (rutin) with β-lactoglobulin (BLG) was carried out by using several optical spectroscopic (UV-visible spectroscopy, fluorescence quenching measurements, synchronous fluorescence, 3D fluorescence spectroscopy and far-UV CD measurements), molecular docking and molecular dynamics (MD) simulation methods. The fluorescence quenching results confirmed that fluorescence intensity of BLG is quenched by rutin and the quenching constant is increased with increase in temperature. The quenching mechanism between rutin-BLG was found to be dynamic in nature. The thermodynamic parameter particularly ΔH0 and ΔS0 obtained through fluorescence measurements clearly indicated that hydrophobic forces are majorly involved in the rutin-BLG interaction. The UV-absorption, synchronous and three-dimensional fluorescence results displayed that the micro-environment of BLG is changed due to rutin interaction. The secondary structure of BLG was found higher in the presence of rutin. Molecular docking results suggested that rutin binds strongly in the internal cavity of BLG at site 1 and superficially at site 2 through both hydrogen bonding and hydrophobic interactions. The binding affinity was found to be higher 5.47 × 106 M−1 for site 1 compared to site 2 (2.86 × 105 M−1). The MD simulation suggested that rutin formed a stable complex with BLG at site 1.This study will explain interacting properties of rutin with carrier BLG proteins and open a new vista for the food industry.