Polarimetric and nuclear magnetic resonance studies of the complexation of mercury by thiols

Shoukry, Mohamed M.; Cheesman, Bruce V.; Rabenstein, Dallas L.

doi:10.1139/v88-492

Cited by 23 publications

(15 citation statements)

References 15 publications

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“…A three coordinate [Hg(GS) 3 ] − and a four coordinate [Cd(GS) 4 ] 2− have been reported [21–23]. Similarly, the complexation of As(III) with glutathione is proposed as a trigonal pyramidal structure, As(GS) 3 , at physiological pH [24].…”

Section: Resultsmentioning

confidence: 99%

Pb-207 NMR spectroscopy reveals that Pb(II) coordinates with glutathione (GSH) and tris cysteine zinc finger proteins in a PbS3 coordination environment

Neupane

Pecoraro

2011

Journal of Inorganic Biochemistry

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207Pb NMR spectroscopy can be used to monitor the binding of Pb(II) to thiol rich biological small molecules such as glutathione and to zinc finger proteins. The UV/visible (UV/Vis) absorption band centered at 334 nM and the observed 207Pb-signal in 207Pb NMR (δ ~ 5750 ppm) indicate that glutathione binds Pb(II) in a trigonal pyramidal geometry (PbS3) at pH 7.5 or higher with a 1:3 molar ratio of Pb(II) to GSH. While previous studies using UV/Vis and extended X-ray absorption fine structure (EXAFS) spectroscopy were interpreted to show that the zinc binding domain from HIV nucleocapsid protein (HIV-CCHC) binds Pb(II) in a single PbS3 environment, the more sensitive 207Pb NMR spectra (at pH 7.0, 1:1 molar ratio) provide compelling evidence for the presence of two PbS3 structures (δ = 5790 and 5744 ppm), one of which is more stable at high temperatures. It has previously been proposed that the HIV-CCHH peptide does not fold properly to afford a PbS2N motif, because histidine does not bind to Pb(II). These predictions are confirmed by the present studies. These results demonstrate the applicability of 207Pb NMR to biomolecular structure determination in proteins with cysteine binding sites for the first time.

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Section: Resultsmentioning

confidence: 99%

Pb-207 NMR spectroscopy reveals that Pb(II) coordinates with glutathione (GSH) and tris cysteine zinc finger proteins in a PbS3 coordination environment

Neupane

Pecoraro

2011

Journal of Inorganic Biochemistry

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“…The previously reported formation constants for the [Hg(AH) 2 ] 2− and [Hg(AH) 3 ] 4− species, log β = 40.95 and 44.18, respectively, show that a tris -thiolate Hg(II) complex with weaker bonding to the (AH) 2− groups than in [Hg(AH) 2 ] 2− , can form at physiological pH in excess of glutathione (8, 18, 19). In the present work, the structure and composition of the Hg(II)-glutathione complexes formed in solution at physiological pH have been studied by combining Hg L III -edge EXAFS and 199 Hg NMR spectroscopy, complemented by ESI-MS.…”

Section: Discussionmentioning

confidence: 98%

“…pH, calculated by means of the available stability constants from the literature (see Appendix I and Refs. (8, 19). Such calculated diagrams confirm that the [Hg(AH) 2 ] 2− and [Hg(AH) 3 ] 4− complexes are the major Hg(II)-GSH species at neutral pH, with the glutathione amine group still being protonated.…”

Section: Discussionmentioning

confidence: 99%

Glutathione Complex Formation with Mercury(II) in Aqueous Solution at Physiological pH

Mah

Jalilehvand

2010

Chem. Res. Toxicol.

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The mercury(II) complexes formed in neutral aqueous solution with glutathione (GSH, here denoted AH3 in its tri-protonated form) were studied using Hg LIII-edge extended X-ray absorption fine structure (EXAFS) and 199Hg NMR spectroscopy, complemented with electrospray ionization mass spectrometric (ESI-MS) analyses. The [Hg(AH)2]2− complex, with the Hg-S bond distances 2.325 ± 0.01 Å in linear S-Hg-S coordination and the 199Hg NMR chemical shift −984 ppm, dominates except at high excess of glutathione. In a series of solutions with CHg(II) ~17 mM and GSH/Hg(II) mole ratios rising from 2.4 to 11.8, the gradually increasing mean Hg-S bond distance corresponds to an increasing amount of the [Hg(AH)3]4− complex. ESI-MS peaks appear at −m/z values of 1208 and 1230 corresponding to the [Na4Hg(AH)2(A)]− and [Na5Hg(AH)(A)2]− species, respectively. In another series of solutions at pH = 7.0 with CHg(II) ~50 mM and GSH/Hg(II) ratios from 2.0 to 10.0, the Hg LIII-edge EXAFS and 199Hg NMR spectra show that at high excess of glutathione (~0.35 mol·dm−3) about ~ 70% of the total mercury(II) concentration is present as the [Hg(AH)3]4− complex, with the average Hg-S bond distance 2.42 ± 0.02 Å in trigonal HgS3 coordination. The proportions of HgSn species, n = 2, 3 and 4, quantified by fitting linear combinations of model EXAFS oscillations to the experimental EXAFS data in our present and previous studies, were used to obtain stability constants for the [Hg(AH)3]4− complex, and also for the [Hg(A)4]10− complex that is present at high pH. For Hg(II) in low concentration at physiological conditions (pH = 7.4, CGSH = 2.2 mM) the relative amounts in the HgS2 species [Hg(AH)2]2−, [Hg(AH)(A)]3− and the HgS3 complex [Hg(AH)3]4− was calculated to be 95 : 2 : 3. Our results are not consistent with the formation of dimeric Hg(II)-GSH complexes proposed in a recent EXAFS study.

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“…Several types of cysteine derivatives (e.g., pencillamine and N -actylcysteine) form soluble complexes and have been suggested as possible detoxification agents [16][17][18][19]. Although mercury(II) being a soft Lewis acid forms quit stable complexes with thiol groups [20][21][22][23], many thiolates remain labile and undergo ligand exchange, which is more pronounced in low (two and three)-coordinate compounds [24,25]. Mercurythiolates provide representative examples of the structural diversity shown by the extensive family of metal thiolates [5][6][7][8]13,[26][27][28].…”

Section: Introductionmentioning

confidence: 99%

Synthesis, spectroscopic characterization and antimicrobial studies of mercury(II) complexes of thiolates

et al. 2009

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Abstract. Mercury(II) complexes of thiolates having the general formula [Hg(RS)Cl 2 ]− and [Hg(RS) 2 ] have been prepared and characterized by IR and NMR ( 1 H and 13 C) spectroscopy (RSH = 2-aminoethanethiol hydrochloride (Aet), cysteine (Cys), thiosalicylic acid (Ts) and 2-mercaptonicotinic acid (Mnt)). The spectral data suggests that the coordination of thiolates to mercury(II) occurs through the sulfur as indicated by the absence of S-H vibrations in IR and significant downfield shifts in the C-S resonance in 13 C NMR. However, in Mnt complexes, coordination through both sulfur and nitrogen is indicated. Antimicrobial activities of the complexes were evaluated by minimum inhibitory concentration and the results showed that the complexes exhibited a wide range of activities against gram-negative bacteria (E. coli, P. aeruginosa), while moderate activity was observed against a mold, P. citrinum.

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Polarimetric and nuclear magnetic resonance studies of the complexation of mercury by thiols

Cited by 23 publications

References 15 publications

Pb-207 NMR spectroscopy reveals that Pb(II) coordinates with glutathione (GSH) and tris cysteine zinc finger proteins in a PbS3 coordination environment

Pb-207 NMR spectroscopy reveals that Pb(II) coordinates with glutathione (GSH) and tris cysteine zinc finger proteins in a PbS3 coordination environment

Glutathione Complex Formation with Mercury(II) in Aqueous Solution at Physiological pH

Synthesis, spectroscopic characterization and antimicrobial studies of mercury(II) complexes of thiolates

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