High Field NMR Study of the Binding of Lead(ii) to Cysteine and Glutathione

Kane‐Maguire, Leon A. P.; Riley, Peter J.

doi:10.1080/00958979308035150

Cited by 21 publications

(34 citation statements)

References 12 publications

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“…This is in contrast to a previous 1 H NMR study of a D 2 O solution containing GSH/Pb 2+ = 2.0 (at pD = 12.9, C Pb 2+ = 5 mM) where the observed Δδ for the Cys β proton was only 0.23-0.35 ppm. 41 These chemical shift differences may indicate that the speciation of Pb 2+ -GSH complexes is different in highly alkaline media, where the amino groups are deprotonated, and hydrolysis of the Pb 2+ ions is also a competing factor. 92 A closer look at Figure 3 shows that the NMR signal observed for Glu α proton in free GSH shifts downfield in the spectrum of solution A , which can be attributed to the Pb 2+ coordination to Glu amine or COO - groups at pH 8.5.…”

Section: Discussionmentioning

confidence: 99%

Lead(II) Complex Formation with Glutathione

2012

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A structural investigation of complexes formed between the Pb2+ ion and glutathione (GSH, denoted AH3 in its triprotonated form) the most abundant non2protein thiol in biological systems, was carried out for a series of aqueous solutions at pH 8.5 and CPb2+ = 10 mM, and in the solid state. The Pb LIII-edge EXAFS oscillation for a solid compound with the empirical formula [Pb(AH2)]ClO4 was modeled with one Pb-S and two short Pb-O bond distances at 2.64 ± 0.04 Å and 2.28 ± 0.04 Å, respectively. In addition Pb···Pb interactions at 4.15 ± 0.05 Å indicate dimeric species in a network where the thiolate group forms an asymmetrical bridge between two Pb2+ ions. In aqueous solution at the mole ratio GSH / Pb(II) = 2.0 (CPb2+ = 10 mM, pH 8.5), lead(II) complexes with two thiolate ligands form, characterized by a ligand-to-metal charge transfer band (LMCT) S- → Pb2+ at 317 nm in the UV-vis spectrum and mean Pb-S and Pb-(N/O) bond distances of 2.65 ± 0.04 Å and 2.51 ± 0.04 Å, respectively, from a Pb LIII-edge EXAFS spectrum. For solutions with higher mole ratios, GSH / Pb(II) ≥ 3.0, ESI-MS spectra identified a trisglutathionyl lead(II) complex, for which Pb LIII-edge EXAFS spectroscopy shows a mean Pb-S distance of 2.65 ± 0.04 Å in PbS3 coordination, 207Pb NMR spectroscopy displays a chemical shift of 2793 ppm, and in the UV-vis spectrum an S- → Pb2+ LMCT band appears at 335 nm. The complex persists at high excess of glutathione, and also at ~25 K in frozen glycerol (33%) / water glasses for GSH / Pb(II) mole ratios from 4.0 to 10 (CPb2+ = 10 mM) measured by Pb LIII-edge EXAFS spectroscopy.

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Section: Discussionmentioning

confidence: 99%

Lead(II) Complex Formation with Glutathione

2012

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“…For example, Cys can be coordinated to Pb 2+ ions in a tridentate fashion in 1:1 complexes, while in 2:1 complexes, it binds in a bidentate fashion. 61 Prompted by these results, we suggested that the concentration of Cys might influence its binding mode, and, consequently, the G-factor intensity of Cys-stabilized QDs.…”

Section: Some Investigations Of Cys Binding Modes On the Surface Ofmentioning

confidence: 91%

Effect of Chiral Ligand Concentration and Binding Mode on Chiroptical Activity of CdSe/CdS Quantum Dots

et al. 2019

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Chiroptically active fluorescent semiconductor nanocrystals, quantum dots (QDs), are of high interest, from a theoretical and technological point of view, because they are promising candidates for a range of potential applications. Optical activity can be induced in QDs by capping them with chiral molecules, resulting in circular dichroism (CD) signals in the range of the QD ultraviolet−visible (UV-vis) absorption. However, the effects of the chiral ligand concentration and binding modes on the chiroptical properties of QDs are still poorly understood. In the present study, we report the strong influence of the concentration of a chiral amino acid (cysteine) on its binding modes upon the surface of CdSe/CdS QDs, resulting in varying QD chiroptical activity and corresponding CD signals. Importantly, we demonstrate that the increase of cysteine concentration is accompanied by the growth of the QD CD intensity, reaching a certain critical point, after which it starts to decrease. The intensity of the CD signal varies by almost an order of magnitude across this range. Nuclear magnetic resonance and Fourier transform infrared data, supported by density functional theory calculations, reveal a change in the binding mode of cysteine molecules from tridentate to bidentate when going from low to high concentrations, which results in a change in the CD intensity. Hence, we conclude that the chiroptical properties of QDs are dependent on the concentration and binding modes of the capping chiral ligands. These findings are very important for understanding chiroptical phenomena at the nanoscale and for the design of advanced optically active nanomaterials.

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“…However, unlike CadA and ZntA, PbrA possesses two heavy metal-associated motifs with the amino acid sequence Cys-ProThr-Glu-Glu instead of the consensus sequence Cys-X-X-Cys (Table 1). This difference, where one Cys is replaced by two Glu, might reflect the preferential coordination of Pb(II) to oxygen rather than to sulfur (2,13).…”

Section: Discussionmentioning

confidence: 99%

Cloning and Functional Analysis of the pbr Lead Resistance Determinant of Ralstonia metallidurans CH34

et al. 2001

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The lead resistance operon, pbr, of Ralstonia metallidurans (formerly Alcaligenes eutrophus) strain CH34 is unique, as it combines functions involved in uptake, efflux, and accumulation of Pb(II). The pbr lead resistance locus contains the following structural resistance genes: (i) pbrT, which encodes a Pb(II) uptake protein; (ii) pbrA, which encodes a P-type Pb(II) efflux ATPase; (iii) pbrB, which encodes a predicted integral membrane protein of unknown function; and (iv) pbrC, which encodes a predicted prolipoprotein signal peptidase. Downstream of pbrC, the pbrD gene, encoding a Pb(II)-binding protein, was identified in a region of DNA, which was essential for functional lead sequestration. Pb(II)-dependent inducible transcription of pbrABCD from the PpbrA promoter is regulated by PbrR, which belongs to the MerR family of metal ion-sensing regulatory proteins. This is the first report of a mechanism for specific lead resistance in any bacterial genus.The presence of toxic heavy metals in the environment has resulted in the development or acquisition by bacteria of genetic systems that counteract their effects. Many bacterial heavy metal resistance systems are based on efflux, and two groups of efflux systems have been identified. These can be either P-type ATPases, e.g., the Cu(II), Cd(II), and Zn(II) ATPases of gram-negative bacteria (31), or chemiosmotic pumps, e.g., the three-component divalent-cation efflux systems cnr, ncc, and czc of Ralstonia metallidurans (formerly Alcaligenes eutrophus) CH34 (35).Lead resistance has been reported in both gram-negative and gram-positive bacteria isolated from lead-contaminated soils, with Pseudomonas marginalis showing extracellular lead exclusion and Bacillus megaterium demonstrating intracellular cytoplasmic lead accumulation (28). Pb(II)-resistant strains of Staphylococcus aureus and Citrobacter freundii that accumulated the metal as an intracellular lead-phosphate have also been isolated (15, 16), though the molecular mechanism of detoxification remains to be elucidated. Efflux of Pb(II) has also been reported for the CadA ATPase of S. aureus and the ZntA ATPase of Escherichia coli (27).R. metallidurans strain CH34 contains at least seven determinants encoding resistances to toxic heavy metals, located on one of the two endogenous megaplasmids, pMOL28 and pMOL30 (for a review, see reference 35). One of these determinants, located on pMOL30 (20), mediates resistance to Pb(II). In this paper we describe the isolation and characterization of the Pb(II) resistance determinant, pbr, from pMOL30. MATERIALS AND METHODSBacterial strains, plasmids, and media. R. metallidurans and E. coli were grown in 869 medium (20) at 30 and 37°C, respectively. Antibiotic resistance was selected on media supplemented with 20 g of tetracycline or 100 g of ampicillin per ml, as appropriate. To test for Pb(II) resistance, cells were grown on RM medium, a modified 284 gluconate minimal medium (20) in which Tris-HCl is replaced by 20 mM morpholinepropanesulfonic acid (MOPS)-NaOH (pH 7) and Na...

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High Field NMR Study of the Binding of Lead(ii) to Cysteine and Glutathione

Cited by 21 publications

References 12 publications

Lead(II) Complex Formation with Glutathione

Lead(II) Complex Formation with Glutathione

Effect of Chiral Ligand Concentration and Binding Mode on Chiroptical Activity of CdSe/CdS Quantum Dots

Cloning and Functional Analysis of the pbr Lead Resistance Determinant of Ralstonia metallidurans CH34

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