Multi-spectroscopic and molecular modelling approach to investigate the interaction of riboflavin with human serum albumin

Abstract

Riboflavin (RF) plays an important role in various metabolic redox reactions in the form of flavin adenine dinucleotide and flavin mononucleotide. Human serum albumin (HSA) is an important protein involved in the transportation of drugs, hormones, fatty acid and other molecules which determine the biodistribution and physiological fate of these molecules. In this study, we have investigated the interaction of riboflavin RF with HSA under simulative physiological conditions using various biophysical, calorimetric and molecular docking techniques. Results demonstrate the formation of riboflavin–HSA complex with binding constant in the order of 10⁴ M⁻¹. Fluorescence spectroscopy confirms intermediate strength having a static mode of quenching with stoichiometry of 1:1. Experimental results suggest that the binding site of riboflavin mainly resides in sub-domain IIA of HSA and that ligand interaction increases the α-helical content of HSA. These parameters were further verified by isothermal titration calorimetry ITC which confirms the thermodynamic parameters obtained by fluorescence spectroscopy. Molecular docking was employed to suggest a binding model. Based on thermodynamic, spectroscopic and computational observations it can be concluded that HSA-riboflavin complex is mainly stabilized by various non-covalent forces with binding energy of −7.2 kcal mol⁻¹.

Keywords:

• riboflavin
• human serum albumin
• calorimetry
• molecular docking

Acknowledgements

Md. Maroof Alam is thankful to University Grants Commission, New Delhi, for the award of BSR-Fellowship. The authors also thank the Department of Biochemistry, Aligarh Muslim University, Aligarh, and Department of Agricultural Microbiology, Aligarh Muslim University, Aligarh for providing the necessary facilities.