In this paper, the interaction of gamma seroglobulinum humanum (GSH) with Ir(IV) has been investigated by using absorption spectra, fluorescence spectroscopy and synchronous fluorescence spectroscopy. In the system of acetic acid-sodium acetate buffer (0.1 mol•L^－1, pH 5.0), Ir(IV) enhanced the intensity of the characteristic absorption peak of GSH, accompanied with red shift, showing that binding of Ir(IV) to GSH had strong impact on protein conformation with decrease of α-helical content of the protein and local perturbation around the hydrophobic binding pocket of tryptophan and tyrosine amino acid residues. The fluorescence intensity of GSH at 342 nm was quenched when Ir(IV) was added, the quenching mechanism of GSH affected by Ir(IV) was a static quenching procedure, and the binding number n and binding constant K were calculated. The effect of Ir(IV) on the conformation of GSH was further analyzed using synchronous fluorescence spectroscopy. The results indicated the perturbation around the tryptophan residues, which was in agreement with that by absorption spectra.

Key words: Ir(IV), gamma seroglobulinum humanum (GSH), absorption spectroscopy, fluorescence spectroscopy, synchronous fluorescence spectroscopy