Hg Cations Research Articles

Glutamate: a potential mediator of inorganic mercury neurotoxicity.

Exposure to mercury vapor (Hg0) produces neurotoxic effects which are for the most part subsequent to its biotransformation in brain to the mercuric cation (Hg2 +), which has an exceptionally strong affinity towards the SH groups in proteins. However, neurologic symptoms are often encountered in subjects in which Hg+ concentration in the brain remains in the submicromolar range, markedly below the anticipated threshold for direct inhibition of cerebral metabolism and function. In this report we review biochemical and morphological evidence obtained in this and other laboratories in tissue culture studies suggesting that in such instances mercury neurotoxicity may be mediated by excitotoxic activity of glutamate (GLU). Mercuric chloride (MC) at 1 microM concentration (or less) inhibits GLU uptake and stimulates GLU release in cultured astrocytes, which in vivo is likely to result in excessive GLU accumulation in the extracellular space of the CNS. Inhibition of GLU uptake and stimulation of GLU release by MC may be attenuated by addition to the cultures of a cell membrane-penetrating agent dithiothreitol (DTT) but not of glutathione (GSH), which is not transported to the inside of the cells. However, MC-stimulated release of GLU is suppressed when the intracellular GSH levels are increased by metabolic manipulation. The results indicate that the MC-vulnerable SH groups critical for GLU transport are located within the astrocytic membranes. Ultrastructural evidence for GLU-mediated MC neurotoxicity came from studies in an organotypic culture of rat cerebellum. We have shown that: 1) 1 microM MC lowers the threshold of GLU neurotoxicity, 2) the combined neurotoxic effect of GLU plus MC is attenuated by DTT but not by GSH, which is consistent with the involvement of impaired astrocytic GLU transport, and 3) neuronal damage induced by GLU plus MC becomes less accentuated in a medium with dizocilpine (MK-801), a noncompetitive NMDA receptor antagonist.

Mixed Layers in Copper Based Superconducting Materials

Recently discovered series of high Tc superconductors, characterized by the existence of two types of cations within the same layer, are presented. The first family concerns the mercury based cuprates, Hg 1-x M x A 2 Ca m-1 Cu m O 2m+2+δ , with A = Ba and/or Sr, which exhibit structures closely related to that of the thallium cuprates TlBa 2 Ca m-1 Cu m O 2m+3 . They differ from the thallium cuprates by a high oxygen deficiency at the level of the mercury layer. It is shown that cations such as M = Cu, Pb, Tl, Bi, Ce, Pr, Cr, V, Mo, W, Ti, Sr, Ca,... can partially substitute for mercury ions, stabilizing the structures. The cationic composition of the layer depends indeed on the nature of the M cation but also on that of the alkaline earth A. For given A and M cations, the x value remains unchanged even when the number of copper layers varies. M and Hg cations are either statistically distributed over the same site or ordered. Different types of ordering have been detected. Another way of generating mixed layers is to shear periodically the structure, leading to the formation of the so called collapsed phase. In the collapsed bismuth cuprates, bismuth and copper segments, a few octahedra long, alternate in strongly waving layers. In the collapsed oxycarbonates, carbonate groups and M cations are ordered within the intermediate layer so that they can be simply described from a partial and ordered substitution of carbon for Hg, Tl, Bi and other M cations building the intermediate layer. The oxycarbonitrates (Y 1-x Ca x ) n Ba 2n Cu 3n-1 (C,N)O 3 O 7n-3 can also be described as an ordered substitution of carbon for copper in the 123 matrix. The different families of superconducting materials which are generated by such mechanisms are described as well as the way the different species are distributed within the mixed layers. Their influence on the physical properties are discussed.

Structural and Thermal Characterization of Zeolite Type Y Modified by Ion Exchange with Zn, Cd, and Hg Cations

AbstractThe object of our studies was zeolite NaY and its Zn2+‐, Cd2+‐ and Hg2+ modifications obtained by ion‐exchange method. Influence of the above cations on the crystalline structure of zeolite type Y and its thermal stability has been shown on the grounds of X‐ray diffraction, differential thermal analysis, and infrared spectroscopic measurements.

Cation and anion disorder in HgBa2Can−1CunO2n+2+δ

Cu and C substitution for Hg in Hg-based cuprate superconductors is discussed. The large Hg Debye-Waller factor usually obtained from refinements based on diffraction data should be interpreted as an indication of carbon substitution for the Hg cations. This assumption is corroborated by HREM, powder x-ray anomalous dispersion, and powder neutron diffraction investigations.

On the possibility of replacing Hg by Cu in the HgBa 2CuO 4+δ phase synthesized under high-pressure

To study the existence of the Hg 1- x Cu x Ba 2CuO 4+δ solid solution, samples with x = 0.00, 0.05, 0.10, 0.15, 0.20, 0.25, and 0.50, were synthesized using a high-pressure and high-temperature technique. These samples have been characterized by X-ray powder diffraction and AC susceptibility measurements. Only the samples with x = 0 and 0.05 were found to be monophase. The sample with x = 0, depending upon the preparation is non-superconducting or has a T c = 50 K. Its lattice parameters show that it is overdoped. All the other samples contain impurities, whose nature and relative quantities depend upon x and the compound used as extra Cu source. From the present results it can be deduced that Hg can in principle be replaced by Cu, but this replacement cannot be more than 10%. The discrepancy between the extra oxygen content determined by iodometric titration (0.13) and that determined by X-ray diffraction (0.20) and the low occupancy factor (or the relatively high thermal parameter) for the Hg cations is explained in terms of the incorporation of CO 3 −2 groups into the structure.

Suppression of superconductivity in Hg-1223 and Hg-1234 by partial replacement of Hg by carbon

Hg based 1223 and 1234 phases were prepared by a high-pressure high-temperature technique using precursors obtained by the decomposition of BaO 2, CaCO 3 and CuO in oxygen flow at 925°C. These phases were found to exhibit much lower T c's (64 K for 1223 phase, and no superconductivity for the 1234 phase) than the corresponding Hg based samples prepared by different precursors and this even after heat treatments in oxygen flow. The structural refinement of this 1223 phase carried out by using synchrotron X-ray powder data revealed a large deficiency on the Hg site; the occupancy factor for this site was found to be 0.69(1). This may be due to the replacement of some of the Hg cations by C. By IR spectroscopy the characteristic frequencies corresponding to the vibrations of the CO 3 −2 group were found in these samples. Large amounts of intergrowth defects were defected by electron microscopy and no superstructure spots were found in the diffraction patterns. The replacement of Hg by C in the structures of the Hg based superconductors induces a decrease of the concentration of the extra oxygen in the (Hg, C) layer bonded to the Hg atoms. Since it is this oxygen which oxidizes the (CuO 2) layers, its decrease causes a reduction of these layers, which is responsible for the decrease of the superconducting transition temperatures.

Corner opening of cyclopropanes by mercury(II) and thallium(III) and transmetalation of the intermediate organomercurials. A novel, stereoselective approach to cyclobutanes and cyclopropanes

The reactivity of the two isoelectronic cations (Hg2+ and T P ) toward the cyclopropane ring is compared, and further evidence for the exclusive corner selectivity for Hg2+ is provided by isotope labeling. Cleavage of cyclopropyl derivative 1 with Hg(NO3)2, followed by KBr quenching, afforded the stable, rearranged organomercurial 3, whose transmetalation has been studied. Whereas reaction of 3 with Pd(I1) afforded lactol 4, treatment with MezCuLi resulted in the formation of cyclobutanol derivative (3 - 29); analogous conjugate addition has also been accomplished (32 - 35). Similarly, the organomercurial 22, obtained from 21 as the major product on the Hg(I1)-mediated ringopening, reacted with MezCuLi or AlC13 to give the ring-closure product 21. These reactions representa novel method for the stereoselective construction of four- and three-membered rings. The stereochemistry of the key steps of these transformations has been established by using stereospecifically deuterated substrates lb, 3b, 21b, and 22b.

Purification and characterization of novel N-acyl-D-aspartate amidohydrolase from Alcaligenes xylosoxydans subsp. xylosoxydans A-6.

Alcaligenes xylosoxydans subsp. xylosoxydans A-6 (Alcaligenes A-6) produced N-acyl-D-aspartate amidohydrolase (D-AAase) in the presence of N-acetyl-D-aspartate as an inducer. The enzyme was purified to homogeneity. The enzyme had a molecular mass of 56 kDa and was shown by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (PAGE) to be a monomer. The isoelectric point was 4.8. The enzyme had maximal activity at pH 7.5 to 8.0 and 50 degrees C, and was stable at pH 8.0 and up to 45 degrees C. N-Formyl (Km = 12.5 mM), N-acetyl (Km = 2.52 mM), N-propionyl (Km = 0.194 mM), N-butyryl (Km = 0.033 mM), and N-glycyl (Km = 1.11 mM) derivatives of D-aspartate were hydrolyzed, but N-carbobenzoyl-D-aspartate, N-acetyl-L-aspartate, and N-acetyl-D-glutamate were not substrates. The enzyme was inhibited by both divalent cations (Hg2+, Ni2+, Cu2+) and thiol reagents (N-ethylmaleimide, iodoacetic acid, dithiothreitol, and p-chloromercuribenzoic acid). The N-terminal amino acid sequence and amino acid composition were analyzed.

Synthesis and selectivity towards divalent inorganic cations of macrocyclic dicarboxamides and disulphonamides bearing pendant electron donor groups

Novel carboxamides and sulphonamides derived from 4,13-diaza-18-crown-6 incorporating ligating groups have been obtained and their ion selectivities have been evaluated by membrane techniques indicating their high affinity for Hg(II) cations.

Electroinitiated cationic polymerization of ε‐caprolactone using sacrificial anodes

AbstractThe polymerization of ϵ‐caprolactone is carried out with metallic cationic initiators generated electrochemically. V, Ti, Cr, Al and Hg cations gave rise to polymers with molecular weights in the range 1 000–13 000. Better yields and higher degrees of polymerization are obtained in the presence of [SbF6]− and [ClO4]− as anion of the supporting electrolyte, which is in accordance with the stability and the poor nucleophilicity of these anions.

Gamma-irradiation effects on the electrical conductivity behaviour of some N,N'-ethylenebis (salicylideneiminato) divalent metal chelates

γ-Irradiation effects on the electrical conductivity behaviour of some newly prepared mono-, homobi- and heterobinuclear metal chelates containing divalent Co, Ni, Cu, Cd and Hg cations of N,N'-ethylenebis (salicylideneimine) H 2SED were investigated. The complexes were identified on the basis of elemental analysis, electronic and infrared spectra. X-Ray diffraction patterns showed that all complexes are well crystalline substances. The variation of the electrical conductivity with temperature was found to be characteristic of an intrinsic semiconductor with impurity centres. The rate constants of the isothermal annealing and the activation energies of the electrical conduction of the irradiated and unirradiated metal chelates were calculated and discussed. It was found that electrical conductivity increases on increasing temperature and decreasing irradiation dose. However, the rate constant of thermal annealing increases in the order mono-, homobi- and heterobinuclear chelates. Seeback effect studies showed that electrons are the majority charge carriers in all irradiated and unirradiated complexes.

Diaza crown ethers bearing heterocyclic ligating groups on nitrogen atoms and their complexing properties with divalent inorganic cations

Two nitrogen-substituted 4,13-diaza-I8-crown-6 compounds, bearing 2-methylquinolyl and 2-methylquinolyl-1-oxide groups, have been prepared. Ionophore-cation selectivities with a range of inorganic divalent cations have been investigated by means of membrane techniques, demonstrating their high selectivity for the Hg(II) cation.

Stabilisation of Hg1-xCdxTe:Hg1-yCdyTex ≠ y) Heterointerfaces and Applications in Infra Red Devices

ABSTRACTThe interface between Hg1-xCdxTe(0 ≦ x ≦ 1) and Hg1-yCdyTe(0 ≦ y ≦ 1) epitaxial layers of different composition (x ≠ y) is unstable with regard to the intermixing of the Hg and Cd cations within the Group II sublattice. This phenomenon may give rise to long-term stability problems in HgTe-(Hg,Cd)Te superlattices and composition grading between (Hg,Cd)Te absorber layers and CdTe buffer or passivation layers in epitaxial infra red detectors. In this paper, a novel approach to the inhibition of interdiffusion in these systems is discussed. This involves the growth of an intervening ZnTe barrier layer at the heterointerface between two (Hg,Cd)Te layers. Initial results are presented which indicate the effectiveness of this technique in reducing interdiffusion in an experimental heterostructure grown by MOVPE. Some possible applications in a variety of HgTe-based long wavelength devices are discussed.

Carbohydrate adducts with zinc-group-metal ions. Interactions of β- d-fructose with Zn(II), Cd(II), and Hg(II) cations, and the effects of metal-ion coordination on the sugar isomer binding

Interaction of β- d-fructose with hydrated salts of zinc-group-metal has been studied in aqueous solution and solid adducts of the type M( d-fructose)X 2· nH 2O, where M = Zn(II), Cd(II), and Hg(II) ions, X = Cl − or Br −, and n = 0–2, have been isolated, and characterized by means of F.t.-i.r. spectroscopy, X-ray powder diffraction, and molar conductivity measurements. The marked spectral similarities observed with the Mg( d-fructose)X 2·4 H 2O (X = Cl − or Br −) compounds indicated that the Zn(II) and Cd(II) ions are six-coordinated, binding to two d-fructose molecules through O-2, O-3 of the first d-fructose, and O-4, O-5 of the second, as well as to two H 2O. The Hg(II) ion binds to two sugar moieties in the same fashion as do the Zn(II) and Cd(II) ions, resulting in four-coordination geometry around the mercury ion. The crystalline sugar is in the β- d-fructopyranose form, and the coordination of the of the Ca(II) ion takes place through the β- d-fructopyranose isomer, whereas the binding of the Mg(II), Zn(II), Cd(II), Hg(II), and UO 2+ 2 cations could be via the β- d-fructopyranose and the β- d-fructofuranose structures.

Intercalation of M F−6 ions (M = Nb, Ta, As, and Sb) into pyrolytic graphite using Hg2+ and Hg2+2 salts

The mercury cation Hg2+ is used to intercalate NbF−6 and TaF−6 anions into pyrolytic graphite (HOPG). The Hg2+ cation in Hg (NbF6)2 and Hg(TaF6)2 oxidizes HOPG to form stage-3 compounds. The Hg2+2 cation is also used as an oxidant to intercalate AsF−6 and SbF−6 ions into graphite. The reduced products of the reactions are identified by Raman spectra. The intercalation compounds are characterized by (00l) x-ray diffraction, and the intercalants are identified with mass spectrometer analysis.

New macrocyclic compounds containing a thiocarbohydrazone grouping

1. New macroheterocyclic compounds containing ether linkages and a thiocarbohydrazone grouping were obtained. The use of Ga and Al salts in the synthesis of these compounds increases their yield, lowers the reaction temperature, and shortens the reaction time. 2. Changes in electronic and IE spectra indicate that the synthesized compounds form complexes with Hg, Ag, Zn, and Ga cations; Hg and Ag cations react with C=S, HN, and C=N groups.

Sugar-metal ion interaction. Synthesis, spectroscopic and structural analysis of Zn(II), Cd(II), and Hg(II) sugar complexes containing l-arabinose

Interaction between l-arabinose and the zinc group metal-ion salts has been studied in aqueous solution and solid complexes of the type M( l-arabinose)X 2· nH 2O, where M = Zn(II), Cd(II), and Hg(II) ions, X = Cl − or Br −, and n = 0–2 have been isolated and characterized. On comparison with the structurally known Ca( l-arabinose) Cl 2·4H 2O and the corresponding magnesium compounds, it is concluded that the Zn(II) and Cd(II) ions are six-coordinated, binding to two arabinose moieties via 03, 04 of the first and 01, 05 of the second sugar molecule as well as to two H 2O molecules. The Hg(II) ion binds only to two sugar molecules in a similar fashion to zinc and cadmium ions, resulting in a four coordination around the mercury ion. The strong intermolecular hydrogen bonding network of the free arabinose is rearranged to that of the sugar OH...H 2O...halide system upon metalation. The β-anomer sugar conformation is predominant in the free sugar, while the α-anomer conformation is preferred by the alkaline earth and Zn(II), Cd(II), and Hg(II) cations.

Studies on K+ permeability of rat gastric microsomes.

A population of gastric membrane vesicles of high K+ permeability and of lower density than endoplasmic tubulovesicles containing (H+-K+)-ATPase was detected in gastric mucosal microsomes from the rat fasted overnight. The K+-transport activity as measured with 86RbCl uptake had a Km for Rb+ of 0.58 +/- 0.11 mM and a Vmax of 13.7 +/- 1.9 nmol/min X mg of protein. The 86Rb uptake was reduced by 40% upon substituting Cl- with SO2-4 and inhibited noncompetitively by ATP and vanadate with a Ki of 3 and 30 microM, respectively; vanadate also inhibited rat gastric (H+-K+)-ATPase but with a Ki of 0.03 microM. Carbachol or histamine stimulation decreased the population of the K+-permeable light membrane vesicles, at the same time increased K+-transport activity in the heavy, presumably apical membranes of gastric parietal cells, and enabled the heavy microsomes to accumulate H+ ions in the presence of ATP and KCl without valinomycin. The secretagogue-induced shift of K+ permeability was blocked by cimetidine, a H2-receptor antagonist. Four characteristics of the K+ permeability as measured with 86RbCl were common in the resting light and the carbachol-stimulated heavy microsomes; (a) Km for +Rb, (b) anion sensitivity (Cl- greater than SO2-4), (c) potency of various divalent cations (Hg2+, Cu2+, Cd2+, and Zn2+) to inhibit Rb+ uptake, and (d) inhibitory effect of ATP, although the nucleotide sensitivity was latent in the stimulated heavy microsomes. The Vmax for 86RbCl uptake was about 10 times greater in the resting light than the stimulated heavy microsomes. These observations led us to propose that secretagogue stimulation induces the insertion of not only the tubulovesicles containing (H+-K+)-ATPase, but also the light membrane vesicles containing KCl transporter into the heavy apical membranes of gastric parietal cells.

Mercury-199 NMR study of the mercury cations (Hg2+, Hg22+, Hg32+, and Hg42+): the first example of mercury-mercury spin-spin coupling

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMercury-199 NMR study of the mercury cations (Hg2+, Hg22+, Hg32+, and Hg42+): the first example of mercury-mercury spin-spin couplingRonald J. Gillespie, Pierre Granger, Keith R. Morgan, and Gary J. SchrobilgenCite this: Inorg. Chem. 1984, 23, 7, 887–891Publication Date (Print):March 1, 1984Publication History Published online1 May 2002Published inissue 1 March 1984https://doi.org/10.1021/ic00175a019RIGHTS & PERMISSIONSArticle Views301Altmetric-Citations41LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (648 KB) Get e-Alerts Get e-Alerts

Ammonium transport in nitrogen-fixing cyanobacterium Nostoc muscorum: Interaction with copper and sulfhydryl agents.

Ammonium (NH4+) uptake in the cyanobacterium Nostoc muscorum ISU (Anabaena ATCC 27893) and interaction of copper (Cu2+) and sulfhydryl agents was studied. N2-grown cells scavenged extracellular NH4+ via two energy-dependent transport systems: the ‘high-’ (Km=11μM, Vmax=0.22nmol/min/mg protein) and ‘low-affinity’ (Km=66μM, Vmax=1.25nmol/min/mg protein). Both transport systems were competitively inhibited by methylamine (high-affinity Ki=20μM; low affinity Ki=80μM), and showed distinct pH profiles. Addition of Cu2+ (0.1μM) stimulated NH4+ uptake by the high-affinity system (Km=8μM, Vmax=0.42nmol/min/mg protein). Similar effect was not observed with other bivalent cations (Hg2+, Ni2+, Zn2+, Mn2+) applied at equimolar concentrations. The sulfhydryl reducing agents, cysteine and dithiothreitol, inhibited the high-affinity system noncompetitively and caused efflux of accumulated NH4+. Cu2+ eliminated the inhibitory effect of sulfhydryl reducing agents on NH4+ uptake. Inhibition of NH4+ uptake by sulfhydryl blocking agents (N-ethylmaleimide or p-chloromercuribenzoate) which was not reversible by Cu2+ suggested that oxidation of available sulfhydryl residues of membrane proteins (carriers) is an important factor in NH4+ translocation in Nostoc muscorum.