Characterizing the interaction between pyrogallol and human serum albumin by spectroscopic and molecular docking methods

In the present study, the interaction of Pyrogallol (PG) with human serum albumin (HSA) was investigated by UV, fluorescence, Circular dichroism (CD), and molecular docking methods. The results of fluorescence experiments showed that the quenching of intrinsic fluorescence of HSA by PG was due to a static quenching. The calculated binding constants (K) for PG-HSA at different temperatures were in the order of 10(4) M (-1), and the corresponding numbers of binding sites, n were approximately equal to unity. The thermodynamic parameters, Delta H and Delta S were calculated to be negative, which indicated that the interaction of PG with HSA was driven mainly by van der Waals forces and hydrogen bonds. The negative value was obtained for Delta G showed that the reaction was spontaneous. In addition, the effect of PG on the secondary structure of HSA was analyzed by performing UV-vis, synchronous fluorescence, and CD experiments. The results indicated that PG induced conformational changes in the structure of HSA. According to Forster no-radiation energy transfer theory, the binding distance of HSA to PG was calculated to be 1.93 nm. The results of molecular docking calculations clarified the binding mode and the binding sites which were in good agreement with the results of experiments. Communicated by Ramaswamy H. Sarma