title: Mercury(II) complex formation with N-acetylcysteine.
abstract: N-Acetylcysteine (H2NAC) is a potent antioxidant, a precursor for cysteine and glutathione, and a potential antidote against certain metal ions such as cadmium and mercury. Little is known about the structural aspects of complexes formed between Hg(II) and N-acetylcysteine, despite many biological tests on its ability to bind to organic and inorganic mercury, and a few reports on formation constants for Hg(NAC)n (n = 1-3) complexes. We have combined several techniques, including Hg L3-edge EXAFS (extended X-ray absorption fine structure), (199)Hg NMR and Raman spectroscopy, to investigate the nature and structure of Hg(II) N-acetylcysteine complexes formed in aqueous solution at pH 7.5 and 10.5. To allow measurements on the same samples, rather concentrated solutions containing CHg(II) = 0.1 M and variable H2NAC/Hg(II) mole ratios = 2.0-10.0 were used. At physiological pH, Hg(NAC)2(2-) and Hg(NAC)3(4-) complexes form, while in ligand excess and at alkaline pH (H2NAC/Hg(II) > 4), a novel tetra-thiolate species Hg(NAC)4(6-) dominates. Comparison between the Hg(II) complex formation with cysteine, penicillamine and N-acetylcysteine in alkaline aqueous solution has been made to elucidate the influence of the blocked amino group of N-acetylcysteine.
authors.affiliation: Department of Chemistry, University of Calgary, Calgary, Alberta T2N 1N4, Canada. faridehj@ucalgary.ca.
authors.forename: Farideh
authors.initials: F
authors.lastname: Jalilehvand
authors.forename: Karnjit
authors.initials: K
authors.lastname: Parmar
authors.forename: Stephen
authors.initials: S
authors.lastname: Zielke
mesh_terms: D000111:Acetylcysteine / Q000737:chemistry*; D005583:Fourier Analysis; D016018:Least-Squares Analysis; D009682:Magnetic Resonance Spectroscopy; D008628:Mercury / Q000737:chemistry*; D012996:Solutions; D013059:Spectrum Analysis, Raman; D056928:X-Ray Absorption Spectroscopy
chemical_list: D012996:Solutions; D008628:Mercury; D000111:Acetylcysteine