Spectroscopic methodologies and computational simulation studies on the characterization of the interaction between human serum albumin and astragalin

In the present work, the interactions of astragalin (AST) with human serum albumin (HSA) were studied systematically thought fluorescence spectra, ultraviolet-visible (UV-vis) absorption spectra, circular dichroism (CD), molecular docking and molecular dynamics (MD) simulations. Fluorescence spectra elaborated that AST reduced the intrinsic fluorescence of HSA through static quenching and non-radiative energy transfer with moderate binding constants in the order of 10(4) mol/L. Thermodynamic parameters and computational simulations elaborated that hydrogen bond, van der Walls force and hydrophobic interaction played a major role in the binding process of AST to HSA. UV-vis absorption, synchronous fluorescence, three-dimensional (3D) fluorescence and CD spectra illustrated that AST disturbed slightly the microenvironment of tryptophan (Trp) and tyrosine (Tyr) residues and decreased alpha-helical structure content. The effect of some biologically significant metal ions, such as Mg2+, Cu2+ and Fe3+, on the binding of AST to HSA was also investigated in detail. Binding displacement and docking studies revealed that AST was located in the binding site I of subdomain IIA in HSA. Finally, MD simulations evaluated the binding stability of the HSA-AST system in a simulated environment. Communicated by Ramaswamy H. Sarma [GRAPHICS] .