- Full (HTML) - Full (PDF) - Related EHP Articles - PubMed:Related Articles - PubMed:Citation - Cited in PMC - Purchase This Issue

Elena Gaggelli,¹ Francesco Berti,¹ Nicola D'Amelio,¹ Nicola Gaggelli,¹ Gianni Valensin,¹ Lucia Bovalini,²
Alessandro Paffetti,² and Lorenza Trabalzini²

¹Department of Chemistry and the NMR Center, and ²Department of Molecular Biology, Biochemistry Section, University of Siena, Siena, Italy

Abstract

The products of hexavalent chromium [Cr(VI) ] reduction by glutathione (GSH) alone or in the presence of equimolar quantities of aspartate (Asp) and/or glutamate (Glu) and a chromium-containing material extracted from bovine liver were studied by ultraviolet-visible spectrum (UV-vis) studies, electrospray mass spectrometry (ES-MS) , electron paramagnetic resonance (EPR) , and nuclear magnetic resonance (NMR) . Reduction of chromate by GSH was followed by UV-vis and NMR, revealing the formation of a paramagnetic complex in which GSH acts as a ligand. ES-MS and EPR measurements provided unequivocal evidence of a dimeric Cr(V) ₂GSH₂ species in which the two metal ions are bridged by the -Glu carboxylate. The analysis of the ¹H and ¹³C shifts experienced by GSH protons and the values of paramagnetic contributions to proton spin-lattice relaxation rates provided a set of constraints for structural determination. The same experiments were repeated in the presence of an equimolar concentration of Asp, revealing the formation of a dimeric Cr(V) paramagnetic complex in which the two metals are now bridged by Asp. Nuclear magnetic resonance dispersion profiles show that water is not displaced by Asp and that the correlation time of this complex is slowed by the increased complexity. When Glu is also included in the solution in equimolar concentration to GSH and Asp, data are consistent with the formation of many mono- and dinuclear species, with the three ligands competing with each other. Finally, the spectroscopic investigation of the chromium-containing material extracted from bovine liver revealed the presence of a complicate mixture of Cr(IV) or Cr(V) complexes, among which some Cr(V) -GSH species are present alone or with other ligands in the metal coordination sphere. Key words: Asp, chromium, electron paramagnetic resonance, electrospray mass spectrometry, Glu, glutathione, LMWCr, nuclear magnetic resonance, ultraviolet-visible spectrum. Environ Health Perspect 110(suppl 5) :733-738 (2002) .

http://ehpnet1.niehs.nih.gov/docs/2002/suppl-5/733-738gaggelli/abstract.html