Redox and ligand exchange reactions of potential gold(I) and gold(III)-cyanide metabolites under biomimetic conditions.
Biomimetic pathways for the oxidation of [Au(CN)(2)](-), a gold metabolite, and further cyanation of the gold(III) products to form Au(CN)(4)(-) were investigated using 13C NMR and UV-Visible spectroscopic methods. Hypochlorite ion, an oxidant released during the oxidative burst of immune cells, was employed. The reaction generates mixed dicyanoaurate(III) complexes, trans-[Au(CN)(2)X(2)](-), where X(-) represents equilibrating hydroxide and chloride ligands, and establishes the chemical feasibility of dicyanoaurate oxidation by OCl(-) to gold(III) species. This oxidation reaction suggests a new procedure for synthesis of H[Au(CN)(2)Cl(2)]. Reaction of trans-[Au(CN)(2)X(2)](-) (X(-)=Cl(-) and Br(-)) or [AuCl(4)](-) with HCN in aqueous solution at pH 7.4 leads directly to [Au(CN)(4)](-) without detection of the anticipated [Au(CN)(x)X(4-x)](-)intermediates, which is attributed to the cis- and trans-accelerating effects of the cyanides. The reduction of [Au(CN)(4)](-) by glutathione and other thiols is a complex, pH-dependent process that proceeds through two intermediates and ultimately generates [Au(CN)(2)](-). These studies provide further insight into the possible mechanisms of an immunogenically generated gold(I)/gold(III) redox cycle in vivo.
Canumalla
A J
AJ
Department of Chemistry, The University of Wisconsin-Milwaukee, Milwaukee, WI 43201-0413, USA.
Al-Zamil
N
N
Phillips
M
M
Isab
A A
AA
Shaw
C F
CF
D003485:Cyanates; D003486:Cyanides / Q000737:chemistry* / Q000378:metabolism*; D005978:Glutathione / Q000378:metabolism; D006046:Gold / Q000737:chemistry* / Q000378:metabolism*; D017612:Gold Compounds / Q000737:chemistry* / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D010084:Oxidation-Reduction; D013056:Spectrophotometry, Ultraviolet; D013816:Thermodynamics
D003485:Cyanates; D003486:Cyanides; D017612:Gold Compounds; C043041:gold cyanide; D006046:Gold; D005978:Glutathione