Interaction of human serum albumin with Fe(III)-deferasirox studied by multispectroscopic methods

The interaction between the iron complex of deferasirox (Fe(III)-DFX) and human serum albumin (HSA) was studied by fluorescence, UV-vis absorption and circular dichroism (CD) spectroscopy. Binding constants, number of binding sites and binding distance (r) were calculated. Fluorescence data at different temperatures revealed that the fluorescence intensity of HSA is decreased in the presence of Fe(III)-DFX complex, and the fluorescence quenching was the result of the formation of the Fe(III)-DFX-HSA complex, therefore the quenching mechanism was static. The binding constant (Ka) for the interaction was 104, and the number of binding site was obtained ~1. The thermodynamic parameters including enthalpy (∆H), entropy (∆S) and Gibb׳s free energy (∆G) changes were calculated according to the van׳t Hoff equation. These data suggested that hydrophobic interaction was the dominant intermolecular force in stabilizing the complex and the association process was spontaneous. The interaction of HSA with Fe(III)-DFX was also confirmed by UV-vis absorption spectra. The quantitative analysis data of CD spectra showed significant alterations of HSA secondary structure in the presence of Fe(III)-DFX complex in aqueous solution with reduction of α-helices content and increase of β-turn structure.