Characterization of interaction between isoliquiritigenin and bovine serum albumin: Spectroscopic and molecular docking methods

The intermolecular interaction between isoliquiritigenin (ISL) and bovine serum albumin (BSA) under imitated physiological conditions was investigated using fluorescence, circular dichromism (CD) and molecular docking methods. The results revealed that the fluorescence quenching of BSA at 338 nm by ISL resulted from the formation of ISL–BSA complex. The number of binding sites (n) for ISL binding on BSA was approximately equal to 1. The experimental and molecular docking results revealed that after binding ISL to BSA, ISL was close to Tyr residue than Trp residue, the binding of ISL to BSA induced a slight change in conformation of BSA but the BSA still retains its secondary structure, the binding process of ISL with BSA is spontaneous, and ISL could be inserted into the hydrophobic cavity of BSA (Site I) in the binding process of ISL with BSA. The enthalpic change (ΔH0) and entropic change (ΔS0) in the process of interaction of BSA with ISL were –116.74 kJ mol–1 and –286.32 J mol–1 K–1, respectively, indicating that the main interaction forces of ISL with BSA were Van der Waals and hydrogen bonding interactions. And, it can be suggested from the molecular docking results that the flexibility of ISL plays an important role in increasing the stability of the whole system upon association of ISL with BSA. -- Highlights: • ISL binds to hydrophobic cavity (site I) in BSA and forms 1:1 complex with it. • The fluorescence quenching of BSA induced by ISL is static quenching. • ISL binding results in a decreased α-helix. • The main interaction forces were Van der Waals and hydrogen bonding interactions. • The flexibility of ISL plays an important role in increasing the ISL–BSA stability