Fluorescence characterization o f human hemoglobin binding with tannic acid

General and Physical Chemistry

Abstract

The nature of the interactions between human hemoglobin (HHb) and tannic acid (TA) has been studied using fluorescence spectroscopy. It has been shown that the quenching mechanism (dynamic or static) of HHb fluorescence in the presence of TA depends on structural changes of protein. Physicochemical characteristics of HHb-TA interactions (Stern-Volmer constant, the binding constant, thermodynamic parameters, Hill coefficient and distance between TA and HHb) have been determined. Thermodynamic analysis suggests that van der Waals forces and hydrogen bonds are the predominant forces in the binding of TA to HHb when the protein molecule has loosen structure, and hydrophobic association plays a major role when the protein molecule is in a nonseparated state.