Binding and conformational changes of human serum albumin upon interaction with 4-aminoantipyrine studied by spectroscopic methods and cyclic voltammetry

• We explored the interaction between 4-aminoantipyrine and HSA by spectroscopic and voltammetric techniques.
• The fluorescence quenching of HSA induced by 4-aminoantipyrine is dynamic quenching.
• The binding constants and thermodynamic parameters were calculated.
• The interaction is driven mainly by hydrophobic force.

The interactions of 4-aminoantipyrine (AAP) with human serum albumin (HSA) have been studied by UV–visible spectroscopy, fluorescence spectroscopy and cyclic voltammetry. The binding of 4-aminoantipyrine quenches the HSA fluorescence, revealing a 1:1 interaction with a binding constant of about 105 M−1. The experimental results showed that AAP effectively quenched the intrinsic fluorescence of HSA via dynamic type of quenching. In addition, according to the synchronous fluorescence spectra of HSA in presence of 4-aminoantipyrine, the tryptophan residue of the proteins are most perturbed by the binding process. The number of binding sites, the binding constant, site probe study, some common metal ions effect and the thermodynamic parameters were calculated.

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