Interaction of uranium(VI) towards glutathione – an example to study different functional groups in one molecule

Abstract

Abstract Glutathione, the most abundant thiol compound of the cell, has a great binding potential towards heavy metal ions. Hence it might influence the distribution of actinides on a cellular level. The unknown strength of the interaction of uranium(VI) with glutathione at physiologically relevant pH is subject of this paper and was studied with UV-vis spectroscopy and time-resolved laser-induced fluorescence spectroscopy (TRLFS). The complex stability constant of UO2H2GS+, logβ 0 121, was calculated to be 39.09 ± 0.15 and 39.04 ± 0.02 in case of UV-vis spectroscopy and TRLFS respectively. Therefore the average formation constant for UO2 2+ + H2GS− = UO2H2GS+ can be assigned to be log K 0 11 = 19.83 ± 0.15. Furthermore it was demonstrated that derivatization of the ligand associated with an enhancement of the ligand's spectroscopic properties can be used for the determination of complex stability constants and to assess the coordination chemistry in more detail. Using UV-vis spectroscopy, the stability constant of the complex between UO2 2+ and glutathione pyruvate S-conjugate, a well absorbing ligand in contrast to glutathione, was calculated to be >39.24 ± 0.08. Furthermore the interaction of UO2 2+ with glutathione derivatized with the fluorescent label monobromobimane was examined with femtosecond laser fluorescence spectroscopy. Thereby the stability constant of the 1:1 complex was determined to be >39.35 ± 0.02. Although the thiol group of glutathione was blocked a strong coordination was found. Thus a significant involvement of the thiol group in the coordination of U(VI) can be excluded.