Biophysical Characterization of Genistein in Its Natural Carrier Human Hemoglobin Using Spectroscopic and Computational Approaches

Steady state and time resolved fluorescence spectroscopy, combined with molecular dynamics simulation, have been used to explore the interactions of a therapeutically important bioflavonoid, genistein, with normal human hemoglobin (HbA). Binding constants estimated from the fluorescence studies were K = (3.5  0.32)  10 M for genistein. Specific interactions with HbA were confirmed from flavonoid-induced fluorescence quenching of the tryptophan in the protein HbA. The mechanism of this quenching involves both static and dynamic components as indicated by: (a) increase in the values of Stern-Volmer quenching constants with temperatures, (b) 0  / is slightly > 1 (where 0  and  are the unquenched and quenched tryptophan fluorescence lifetimes (averaged) respectively). Molecular docking and dynamic simulations reveal that genistein binds between the subunits of HbA, ~18 Å away from the closest heme group of chain α1, emphasizing the fact that the drug does not interfere with oxygen binding site of HbA.