Multispectral and molecular docking studies on the interaction of human serum albumin with iohexol

Abstract

Interaction between iohexol and human serum albumin (HSA) was studied by using some spectroscopic and molecular docking methods at different temperatures (298, 303, 310 and 318K) under physiological pH. Fluorescence quenching was the result of the collision between fluorophore and the iohexol and dynamic quenching mechanism was dominant. The binding constant (K~103) and the number of binding sites (n~1) were also obtained from fluorescence titration data. The thermodynamic parameters namely enthalpy change (ΔH), Gibbs free energy change (ΔG), and entropy change (ΔS) were calculated and the results suggested that hydrophobic interaction was the significant intermolecular force between HSA and iohexol. FT-IR analyses showed that interaction iohexol with HSA caused a conformational change of the protein. The CD spectra revealed major alterations in the secondary structure of HSA with increase of α-helices content and reduction of β-turn. Binding distance between iohexol and HSA was calculated by the Förster Resonance Energy Transfer (FRET) method. The site marker competitive experiments suggested that the binding site of iohexol and HSA was probably located on sites I and II. Results determined by molecular docking method were in agreement with thermodynamic and spectroscopic data and confirmed the binding mechanism of iohexol to HSA.