Interaction of coomassie brilliant blue G250 with human serum albumin: Probing of the binding mechanism and binding site by spectroscopic and molecular modeling methods

The interaction between coomassie brilliant blue G250 and human serum albumin was investigated by spectroscopic methods such as fluorescence quenching, synchronous fluorescence, 3D fluorescence spectra, circular dichroism spectra and UV–vis absorption as well as molecular modeling. The fluorescence quenching of human serum albumin by coomassie brilliant blue G250 was attributed to static interaction. The binding reaction was mainly enthalpy-driven. Both van der Waals and hydrogen bonding forces played major roles in stabilizing the coomassie brilliant blue G250–human serum albumin complex. The Stern–Volmer quenching constant (KSV) and corresponding thermodynamic parameters (ΔHΘ, ΔGΘ and ΔSΘ) were determined. Site marker competitive experiments indicated that coomassie brilliant blue G250 bound to site I (subdomain IIA) of human serum albumin. Molecular docking study further confirmed the binding mode obtained by experimental study. The conformational investigation demonstrated very minor micro-environmental and conformational changes in human serum albumin molecules.