XAS examination of glutathione–cobalt complexes in solution

• We investigated cobalt–glutathione system in solution in neutral and basic conditions.
• We used mainly XAS to examine the coordination mode and the oxidation state of cobalt.
• We performed DFT calculations and NMR experiments to support XAS study in basic pH.

In the present work, we have investigated the coordination modes of cobalt with glutathione (γ-l-glutamyl-l-cysteinyl-glycine, GSH). A systematic study of cobalt–GSH complexes at basic and neutral pH has been undertaken with a multi-spectroscopic approach combined with quantum chemistry calculations. XAS (x-ray absorption spectroscopy) has been performed at the cobalt K edge in order to shed light into the cation coordination sphere and formal oxidation states. XANES (x-ray absorption near edge structure) enabled to show that in basic and neutral media, cobalt oxidation state is equal to + III and + II respectively. EXAFS (extended x-ray absorption fine structure) provided indications on the donor atoms involved in the coordination with cobalt as well as the bond lengths. DFT (density functional theory)-based calculations and NMR experiments have been performed to assess the most stable structure of the cobalt–GSH complex in basic conditions.

Combined XAS, NMR and DFT investigation of cobalt–glutathione complexes at neutral and basic pH is described. Information on the cation coordination sphere, formal oxidation state and most probable conformation of the Co(III)–GSH complex (shown) has been assessed.Figure optionsDownload as PowerPoint slide