Thematische Bibliographien / Bivalent metal cations

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Auswahl der wissenschaftlichen Literatur zum Thema „Bivalent metal cations“

Autor: Grafiati

Veröffentlicht am 18. Mai 2024

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Zeitschriftenartikel zum Thema "Bivalent metal cations"

Yeung, I. Y. L., E. Phillips, D. A. Mann und C. H. Barton. „Oxidant regulation of the bivalent cation transporter Nramp1“. Biochemical Society Transactions 32, Nr. 6 (26.10.2004): 1008–10. http://dx.doi.org/10.1042/bst0321008.

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Nramp1 (murine natural resistance-associated macrophage protein 1 gene)/Slc11a1 (solute carrier family 11 member a1 gene) encodes a bivalent-metal/iron transporter that is expressed within late endosomes/lysosomes of macrophages. A functionally null Nramp1 allele that exhibits impaired bivalent cation transport enables excessive growth of intracellular pathogens. Iron is important for many cellular activities, including defence against pathogens; however, redox-active/free iron can participate in Fenton chemistry that generates reactive oxygen species. Using Raw264.7 cells, non-functional for Nramp1, and stable Nramp1 transfectants, we have examined the effects of impaired bivalent cation transport on macrophage function using glutathione depletion as OS (oxidant stress). Our results demonstrate that OS itself is a signal for increasing Nramp1 transcription and that Nramp1 expression protects against OS. We suggest that OS-mediated protection by Nramp1 function may arise from direct removal of redox-active bivalent cations from a cytosolic pool. We show that OS transcriptional responses are probably mediated by the Sp1 transcription factor.

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Rowatt, E., und R. J. P. Williams. „The interaction of cations with the dye arsenazo III“. Biochemical Journal 259, Nr. 1 (01.04.1989): 295–98. http://dx.doi.org/10.1042/bj2590295.

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1. The dye arsenazo III combines with a selection of cations to give an altered absorption spectrum. 2. Large metal cations such as Ca2+, La3+ and quadrivalent cations give a 1:1 complex with two new absorption peaks at about 610 nm and 655 nm and a KD of about 10(-6) M. 3. Aliphatic polyamines and complex cobalt ions give a 1:1 complex, with one absorption peak at about 610 nm and a KD from 10(-6) to 10(-3) M. 4. Small metal cations finally form a 2:1 complex and also have one absorption peak at about 610 nm, but with a KD of 10(-5)-10(-4) M. 5. The absorption peak at 610 nm is similar to that formed at high pH in the absence of bivalent cations and is due to ionization of phenolic groups with the dye molecule in an extended form. 6. The peak at 655 nm with 1:1 complex can be explained as a change in orientation of the diazo bonds caused by a conformational change of the molecule when it wraps around the single atom of Ca2+ or other large cation.

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GOSWAMI, Tapasree, Arin BHATTACHARJEE, Paul BABAL, Susan SEARLE, Elizabeth MOORE, Ming LI und Jenefer M. BLACKWELL. „Natural-resistance-associated macrophage protein 1 is an H+/bivalent cation antiporter“. Biochemical Journal 354, Nr. 3 (08.03.2001): 511–19. http://dx.doi.org/10.1042/bj3540511.

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In mammals, natural-resistance-associated macrophage protein 1 (Nramp1) regulates macrophage activation and is associated with infectious and autoimmune diseases. Nramp2 is associated with anaemia. Both belong to a highly conserved eukaryote/prokaryote protein family. We used Xenopus oocytes to demonstrate that, like Nramp2, Nramp1 is a bivalent cation (Fe2+, Zn2+ and Mn2+) transporter. Strikingly, however, where Nramp2 is a symporter of H+ and metal ions, Nramp1 is a highly pH-dependent antiporter that fluxes metal ions in either direction against a proton gradient. At pH9.0, oocytes injected with cRNA from wild-type murine Nramp1 with a glycine residue at position 169 (Nramp1G169; P = 3.22×10-6) and human NRAMP1 (P = 3.87×10-5) showed significantly enhanced uptake of radiolabelled Zn2+ compared with water-injected controls. At pH5.5, Nramp1G169 (P = 1.34×10-13) and NRAMP1 (P = 1.09×10-6) oocytes showed significant efflux of Zn2+. Zn2+ transport was abolished when the proton gradient was dissipated using carbonyl cyanide p-trifluoromethoxyphenylhydrazone. Using pre-acidified oocytes, currents of 130±57 nA were evoked by 100µM Zn2+ at pH7.5, and 139±47 nA by 100µM Fe2+ at pH7.0, in Nramp1G169 oocytes; currents of 254±49 nA and 242±26 nA were evoked, respectively, in NRAMP1 oocytes. Steady-state currents evoked by increasing concentrations of Zn2+ were saturable, with apparent affinity constants of approx. 614nM for Nramp1G169 and approx. 562nM for NRAMP1 oocytes, and a curvilinear voltage dependence of transporter activity (i.e. the data points approximate to a curve that approaches a linear asymptote). In the present study we propose a new model for metal ion homoeostasis in macrophages. Under normal physiological conditions, Nramp2, localized to early endosomal membranes, delivers extracellularly acquired bivalent cations into the cytosol. Nramp1, localized to late endosomal/lysosomal membranes, delivers bivalent cations from the cytosol into this acidic compartment where they may directly affect antimicrobial activity.

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AGRANOFF, Daniel, Lauren COLLINS, David KEHRES, Tom HARRISON, Michael MAGUIRE und Sanjeev KRISHNA. „The Nramp orthologue of Cryptococcus neoformans is a pH-dependent transporter of manganese, iron, cobalt and nickel“. Biochemical Journal 385, Nr. 1 (14.12.2004): 225–32. http://dx.doi.org/10.1042/bj20040836.

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Cryptococcus neoformans is an important human opportunistic pathogen and a facultative intracellular parasite, particularly in HIV-infected individuals. Little is known about metal ion transport in this organism. C. neoformans encodes a single member of the Nramp (natural resistance-associated macrophage protein) family of bivalent cation transporters, known as Cramp, which we have cloned and expressed in Xenopus laevis oocytes and Spodoptera frugiperda Sf 21 insect cells. Cramp induces saturable transport of a broad range of bivalent transition series cations, including Mn2+, Fe2+, Co2+ and Ni2+. Maximal cation transport occurs at pH 5.5–6.0, consistent with the proton gradient-based energetics of other Nramp orthologues. Mn2+ transport is diminished in the presence of 140 mM Na+, compatible with a Na+ slippage mechanism proposed for the Saccharomyces cerevisiae Nramp orthologue Smf1p. Cramp resembles Smf1p with respect to predicted membrane topology, substrate specificity and pH dependence, but differs in terms of its apparent affinity for Mn2+ and negligible inhibition by Zn2+. Cramp is the first Nramp orthologue from a fungal pathogen to be functionally characterized. Insights afforded by these findings will allow the formulation of new hypotheses regarding the role of metal ions in the pathophysiology of cryptococcosis.

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Lasia, Andrzej. „Study of the CEE mechanism by voltammetry and chronoamperometry“. Canadian Journal of Chemistry 64, Nr. 12 (01.12.1986): 2319–23. http://dx.doi.org/10.1139/v86-381.

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The electroreduction of bivalent metal cations may proceed by a CEE mechanism with a heterogenous chemical reaction on the electrode surface. The applications of the convolutive linear sweep voltammetry and chronoamperometry to study that mechanism are presented. The behaviour of the electrochemical reactions was simulated using an implicit finite difference technique for different values of kinetic parameters. The simulated curves were analysed and an agreement between the introduced and obtained data was found.

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Field, A. M., E. Rowatt und R. J. P. Williams. „The interaction of cations with lipopolysaccharide from Escherichia coli C as shown by measurement of binding constants and aggregation reactions“. Biochemical Journal 263, Nr. 3 (01.11.1989): 695–702. http://dx.doi.org/10.1042/bj2630695.

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Lipopolysaccharide from Escherichia coli C interacts with polyvalent cations at low ionic strength at more than one site. The first site has high affinity with a KD value of 10(-8) M for Ca2+ and even stronger binding for [(NH3)5CoNH2Co(NH3)5]5+ and La3+. The high-affinity site for the latter cations is beyond the sensitivity of the assay method. The second, low-affinity, site for bivalent cations has a Km of 10(-3) M, whereas, for tervalent and quinquevalent metal cations and spermine and hexacyclen (1,4,7,10,13,16-hexa-azacyclo-octadecane), this constant has a value of 10(-5) M. Binding of cations to the high-affinity site does not alter the aggregation state of the lipopolysaccharide, but combination with the low-affinity site gives particles twice the size of those of the sodium salt. Very high Ca2+ concentrations (30 mM) give particles eight times the size of those of the sodium salt.

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Bie?kowski, Tomasz, Agnieszka Brodzik-Bie?kowska und Witold Danikiewicz. „Complexes of bivalent metal cations in electrospray mass spectra of common organic compounds“. Journal of Mass Spectrometry 37, Nr. 6 (2002): 617–22. http://dx.doi.org/10.1002/jms.322.

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Kar, L., P. Matsumura und M. E. Johnson. „Bivalent-metal binding to CheY protein. Effect on protein conformation“. Biochemical Journal 287, Nr. 2 (15.10.1992): 521–31. http://dx.doi.org/10.1042/bj2870521.

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CheY is a 14 kDa cytoplasmic protein that is activated by the transfer of a phosphoryl moiety to Asp-57 from phosphoCheA during signal transduction in bacterial chemotaxis. It has been established that metal ions are necessary for the autophosphorylation of CheA, the transfer of phosphate from phosphoCheA to CheY and the autodephosphorylation of phosphoCheY. In this work, paramagnetic relaxation enhancement has been used in conjunction with one- and two-dimensional n.m.r. to study the interaction of CheY with bivalent metal ions. These studies have led to the discovery of two conformations of the protein in water, corresponding to the metal-free and the metal-bound states. Binding of bivalent cations like Mg2+, Ca2+, Sr2+, Zn2+ and Mn2+ results in a conformational change from the metal-free to the metal-bound state. Preliminary assignments of the aromatic proton resonances are reported. Comparison of phase-sensitive double-quantum-filtered COSY, homonuclear Hartmann-Hahn coherence transfer and nuclear Overhauser enhancement spectra from the metal-bound and metal-free protein indicates that Trp-58, Thr-87 and Tyr-106 are particularly affected by the conformational change involved, and that this change is limited to a small number of residues. In addition, homonuclear Hartmann-Hahn coherence transfer experiments with paramagnetic Mn2+ show significant suppression of cross-peaks associated with Trp-58 and several neighbouring residues. Comparison of the distances estimated using n.m.r. with the CheY crystal structure indicates that the n.m.r. results are consistent with bivalent metal binding at the cluster of aspartic acid residues that includes Asp-13 and Asp-57. These studies also demonstrate the utility of paramagnetic metal-induced relaxation in conjunction with two-dimensional n.m.r. measurements for exploring ligand-binding sites.

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Veiga, Nicolás, Julia Torres, Carla Bazzicalupi, Antonio Bianchi und Carlos Kremer. „The copper(ii)–phytate–terpyridine ternary system: the first crystal structures showing the interaction of phytate with bivalent metal and ammonium cations“. Chem. Commun. 50, Nr. 95 (2014): 14971–74. http://dx.doi.org/10.1039/c4cc07226j.

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This work reports the solution and crystallographic study of the Cu(ii)–phytate–terpyridine systems, showing for the first time the phytate binding mode toward a bivalent cation and protonated polyamine groups.

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Plazinski, Wojciech, und Mateusz Drach. „Binding of bivalent metal cations by α-l-guluronate: insights from the DFT-MD simulations“. New Journal of Chemistry 39, Nr. 5 (2015): 3987–94. http://dx.doi.org/10.1039/c4nj02206h.

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Dissertationen zum Thema "Bivalent metal cations"

Chaudhury, Rajat Narayan. „Physico-chemical studies on the interaction of bivalent metal cations with natural and snthetic humic substances“. Thesis, Physico-chemical studies on the interaction of bivalent metal cations with natural and snthetic humic substances, 1985. http://hdl.handle.net/123456789/1034.

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Buchteile zum Thema "Bivalent metal cations"

Zhidomirov, G. M., A. A. Shubin, A. V. Larin, S. E. Malykhin und A. A. Rybakov. „Molecular Models of the Stabilization of Bivalent Metal Cations in Zeolite Catalysts“. In Practical Aspects of Computational Chemistry I, 579–643. Dordrecht: Springer Netherlands, 2011. http://dx.doi.org/10.1007/978-94-007-0919-5_20.

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Sposito, Garrison. „Soil Minerals“. In The Chemistry of Soils. Oxford University Press, 2016. http://dx.doi.org/10.1093/oso/9780190630881.003.0006.

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The chemical elements in soil minerals occur typically as charged species arranged in spatial configurations held together by ionic bonds. Ionic bonds involve atoms that retain their unique “electron clouds” and, therefore, they are weaker than covalent bonds, which involve significant mixing of the electron clouds of the bonding atoms, leading to the electron sharing that makes covalent bonds stronger. However, ionic and covalent bonds are idealizations that real chemical bonds only approximate. A real chemical bond shows some degree of ionic character, which maintains the electronic identity of the bonding partners, and some degree of electron sharing, which blurs their electronic identity. The Si—O bond, for example, is said to be an even partition between ionic and covalent character, and the Al—O bond is thought to be about 40% covalent and 60% ionic. Aluminum, however, is exceptional. Almost all the metal–oxygen bonds that occur in soil minerals are ionic. For example, Mg—O and Ca—O bonds are considered to be 75% to 80% ionic whereas Na—O and K—O bonds are 80% to 85% ionic. Covalence thus plays a minor role in determining the atomic structures of soil minerals, aside from the important feature that Si—O bonds, being 50% covalent, impart mineral resistance to weathering, as discussed in Section 1.3. Given this perspective on bonding, the two most important properties of the chemical elements in soil minerals should be their ionic valence and radius. Valence is the ratio of the electric charge on an ionic species to the charge on the proton. Ionic radius is a less direct concept, because the radius of a single ion cannot be measured. Accordingly, ionic radius is a defined quantity based on the following three assumptions: (1) the radius of the bivalent oxygen ion (O2-)in all minerals is 0.140 nm, (2) the sum of radii of the cation and anion participating in a chemical bond equals the measured interatomic distance between the two, and (3) the ionic radius has the same value in all mineral structures containing an ion with a given coordination number (CN).

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