Silver(I) Complex Formation with Cysteine, Penicillamine, and Glutathione

Abstract

The complex formation between silver(I) and cysteine (H2Cys), penicillamine (H2Pen) or glutathione (H3Glu) in alkaline aqueous solution was examined using extended X-ray absorption fine structure (EXAFS) and 109Ag NMR spectroscopic techniques. The complexes formed in 0.1 mol·dm−3 Ag(I) solutions with cysteine and penicillamine were investigated for ligand/Ag(I) (L/Ag) mole ratios increasing from 2.0 to 10.0. For the series of cysteine solutions (pH 10 - 11) a mean Ag-S bond distance 2.45 ± 0.02 Å consistently emerged, while for penicillamine (pH 9) the average Ag-S bond distance gradually increased from 2.40 to 2.44 ± 0.02 Å. EXAFS and 109Ag NMR spectra of a concentrated Ag(I)-cysteine solution (CAg(I) = 0.8 mol·dm−3, L/Ag = 2.2) showed the mean Ag-S bond distance 2.47 ± 0.02 Å and δ(109Ag) = 1103 ppm, consistent with prevailing, partially oligomeric AgS3 coordinated species, while for penicillamine (CAg(I) = 0.5 mol·dm−3, L/Ag = 2.0) the mean Ag-S bond distance 2.40 ± 0.02 Å and δ(109Ag) = 922 ppm indicate that mononuclear AgS2 coordinated complexes dominate. For Ag(I)-glutathione solutions (CAg(I) = 0.01 mol·dm−3, pH ~ 11), mononuclear AgS2 coordinated species with the mean Ag-S bond distance 2.36 ± 0.02 Å dominate for L/Ag mole ratios from 2.0 to 10.0. The crystal structure of the silver(I)-cysteine compound (NH4)Ag2(HCys)(Cys)·H2O (1) precipitating at pH ~ 10 was solved and showed a layer structure with both AgS3 and AgS3N coordination to the cysteinate ligands. A redetermination of the crystal structure of Ag(HPen)·H2O (2) confirmed the proposed digonal AgS2 coordination environment to bridging thiolate sulfur atoms in polymeric intertwining chains forming a double helix. A survey of Ag-S bond distances for crystalline Ag(I) complexes with S-donor ligands in different AgS2, AgS2(O/N) and AgS3 coordination environments was used, together with a survey of 109Ag NMR chemical shifts, to assist assignments of the Ag(I) coordination in solution.

Voltammetric Detection of Captopril on Graphite Screen Printed Electrodes

“…Given the strong interaction between thiols and silver ions 41–44, the question arises to if the behaviour observed for captopril at a GSPE is similar for the other common thiols. Therefore, four other common thiols were oxidised at a GSPE in 0.1 M KNO 3 at 50 mV s −1 .…”

Exposure-dependent Ag+release from silver nanoparticles and its complexation in AgS2sites in primary murine macrophages

“…Our XANES results suggest that silver populates mainly two binding sites in the exposed macrophages: one is AgNP-like and the other is AgGSH-like. dependent on the stoichiometry, pH, and phase of the complex; 15 it is therefore necessary to characterize the Ag coordination sphere in our model AgGSH compound before defining the model to fit to the spectra acquired in cellular environments. 19 The geometry of the AgS x coordination sphere in Ag : GSH complexes is strongly Fig.…”

“…9 The present context fosters the need to develop experimental solutions aimed at disclosing the fate of AgNPs in cellulo, namely their dissolution rate, the chemistry of the released Ag + ions, and the nature of the biomolecules involved in Ag + binding; this information would help in elucidating the molecular and cellular basis of nanoparticle toxicity. 14 At the molecular level, Ag complexation with sulfur organics has been characterized in basic solutions 15 and in crystallized samples: 14,16 Ag is found in digonal AgS 2 and trigonal AgS 3 binding sites organized in extended networks or in compact ring structures; Leung et al 15 provided a survey of Ag-S bond distances from the Cambridge Structural Database (CSD), 17 which reveals two distinct average characteristic bond lengths for Ag-S in digonal or trigonal sites. 10,11 In intracellular compartments, the most potent thiol-containing ligands that might form complexes with Ag + ions are metallothioneins, glutathione (GSH) and cysteine.…”

Glutathione binding to dirhodium tetraacetate: a spectroscopic, mass spectral and computational study of an anti-tumour compound

“…This tendency to bind soft metals also extends to the wide range of metals used in therapeutic complexes, for example, Ag(I), Bi(III), Pt(II) in cisplatin, and Au(I) in Auranofin 10,12,[23][24][25][26] . A marked increase in glutathione synthesis is often correlated with cisplatin resistance, such as the case in human ovarian cancers 10,27,28 .…”