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Alkali Metal

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Hana Sychrová – One of the best experts on this subject based on the ideXlab platform.

  • fluconazole affects the Alkali Metal cation homeostasis and susceptibility to cationic toxic compounds of candida glabrata
    Microbiology, 2014
    Co-Authors: Hana Elicharova, Hana Sychrová


    Candida glabrata is a salt-tolerant and fluconazole (FLC)-resistant yeast species. Here, we analyse the contribution of plasma-membrane AlkaliMetal-cation exporters, a cation/proton antiporter and a cation ATPase to cation homeostasis and the maintenance of membrane potential (ΔΨ). Using a series of single and double mutants lacking CNH1 and/or ENA1 genes we show that the inability to export potassium and toxic AlkaliMetal cations leads to a slight hyperpolarization of the plasma membrane of C. glabrata cells; this hyperpolarization drives more cations into the cells and affects cation homeostasis. Surprisingly, a much higher hyperpolarization of C. glabrata plasma membrane was produced by incubating cells with subinhibitory concentrations of FLC. FLC treatment resulted in a substantially increased sensitivity of cells to various cationic drugs and toxic cations that are driven into the cell by negative-inside plasma-membrane potential. The effect of the combination of FLC plus cationic drug treatment was enhanced by the malfunction of AlkaliMetal-cation transporters that contribute to the regulation of membrane potential and cation homeostasis. In summary, we show that the combination of subinhibitory concentrations of FLC and cationic drugs strongly affects the growth of C. glabrata cells.

  • Alkali Metal cation influx and efflux systems in nonconventional yeast species
    Fems Microbiology Letters, 2011
    Co-Authors: José Ramos, Joaquin Arino, Hana Sychrová


    To maintain optimal intracellular concentrations of AlkaliMetal–cations, yeast cells use a series of influx and efflux systems. Nonconventional yeast species have at least three different types of efficient transporters that ensure potassium uptake and accumulation in cells. Most of them have Trk uniporters and Hak K+–H+ symporters and a few yeast species also have the rare K+ (Na+)-uptake ATPase Acu. To eliminate surplus potassium or toxic sodium cations, various yeast species use highly conserved Nha Na+ (K+)/H+ antiporters and Na+ (K+)-efflux Ena ATPases. The potassium-specific yeast Tok1 channel is also highly conserved among various yeast species and its activity is important for the regulation of plasma membrane potential.

  • Alkali Metal cation transport and homeostasis in yeasts
    Microbiology and Molecular Biology Reviews, 2010
    Co-Authors: Joaquin Arino, José Ramos, Hana Sychrová


    Summary: The maintenance of appropriate intracellular concentrations of Alkali Metal cations, principally K+ and Na+, is of utmost importance for living cells, since they determine cell volume, intracellular pH, and potential across the plasma membrane, among other important cellular parameters. Yeasts have developed a number of strategies to adapt to large variations in the concentrations of these cations in the environment, basically by controlling transport processes. Plasma membrane high-affinity K+ transporters allow intracellular accumulation of this cation even when it is scarce in the environment. Exposure to high concentrations of Na+ can be tolerated due to the existence of an Na+, K+-ATPase and an Na+, K+/H+-antiporter, which contribute to the potassium balance as well. Cations can also be sequestered through various antiporters into intracellular organelles, such as the vacuole. Although some uncertainties still persist, the nature of the major structural components responsible for Alkali Metal cation fluxes across yeast membranes has been defined within the last 20 years. In contrast, the regulatory components and their interactions are, in many cases, still unclear. Conserved signaling pathways (e.g., calcineurin and HOG) are known to participate in the regulation of influx and efflux processes at the plasma membrane level, even though the molecular details are obscure. Similarly, very little is known about the regulation of organellar transport and homeostasis of Alkali Metal cations. The aim of this review is to provide a comprehensive and up-to-date vision of the mechanisms responsible for Alkali Metal cation transport and their regulation in the model yeast Saccharomyces cerevisiae and to establish, when possible, comparisons with other yeasts and higher plants.

Richard A Bartsch – One of the best experts on this subject based on the ideXlab platform.

  • side arm participation in lariat ether carboxylate Alkali Metal cation complexes in solution
    Tetrahedron, 2005
    Co-Authors: Lokman Torun, Thomas W Robison, Jan Krzykawski, David W Purkiss, Richard A Bartsch


    Abstract Lariat ether carboxylic acids of structure CECH2OCH2C6H4–2-CO2H with crown ether (CE) ring sizes of 12-crown-4, 15-crown-5 and 18-crown-6 are prepared and converted into Alkali Metal–lariat ether carboxylate complexes. Absorptions for the diastereotopic benzylic protons in the 1H NMR spectra of the complexes in CDCl3 are utilized to probe the extent of side arm interaction with the crown ether-complexed Metal ion as a function of the crown ether ring size and identity of the Alkali Metal cation.

  • influence of structural variation in room temperature ionic liquids on the selectivity and efficiency of competitive Alkali Metal salt extraction by a crown ether
    Analytical Chemistry, 2001
    Co-Authors: Sangki Chun, And Sergei V Dzyuba, Richard A Bartsch


    An improved method for the preparation of 1-alkyl-3-methylimidazolium hexafluorophosphates provides a series of room-temperature ionic liquids (RTILs) in which the 1-alkyl group is varied systematically from butyl to nonyl. For competitive solvent extraction of aqueous solutions of Alkali Metal chlorides with solutions of dicyclohexano-18-crown-6 (DC18C6) in these RTILs, the extraction efficiency generally diminished as the length of the 1-alkyl group was increased. Under the same conditions, extraction of Alkali Metal chlorides into solutions of DC18C6 in chloroform, nitrobenzene, and 1-octanol was undetectable. The extraction selectivity order for DC18C6 in the RTILs was K+ > Rb+ > Cs+ > Na+ > Li+. As the alkyl group in the RTIL was elongated, the K+/Rb+ and K+/Cs+ selectivities exhibited general increases with the larger enhancement for the latter. For DC18C6 in 1-octyl-3-methylimidazolium hexafluorophosphate, the Alkali Metal cation extraction selectivity and efficiency were unaffected by variation of…

  • new lipophilic crown ethers with intraannular carboxylic acid groups synthesis and Alkali Metal cation extraction
    Journal of Heterocyclic Chemistry, 2000
    Co-Authors: Larry D Bratton, Richard A Bartsch


    A six-step synthetic route to four lipophilic crown ethers with intraannular carboxylic acid groups and ring sizes of 15-crown-4, 18-crown-5, 21-crown-6 and 24-crown-7 is described. Eight new polyether compounds that bear inward-facing bromo and formate ester substituents are prepared as synthetic intermediates. Selectivities and efficiencies of the four new lipophilic crown ether carboxylic acids in competitive Alkali Metal cation extraction from aqueous solutions into chloroform are evaluated.

Robe C Haddo – One of the best experts on this subject based on the ideXlab platform.

  • electronic structure conductivity and superconductivity of Alkali Metal doped c60
    Pure and Applied Chemistry, 1993
    Co-Authors: Robe C Haddo


    The curvature and topology required for fullerene formation strongly enhances the electronegativity of the carbon clusters and as a result c60 readily accepts electrons. Solid c60 undergoes doping with Alkali Metal vapors to produce intercalation compounds which are conductors.During the doping process the predominant phases present are: C60r and A&). The compounds are formed from c60 by occupancy of the interstitial sites of the fcc lattice.These phases constitute the first three-dimensional organic conductors and for A = K, Rb, the A3C6, compounds are superconductors.

  • electronic structure conductivity and superconductivity of Alkali Metal doped c60
    Accounts of Chemical Research, 1992
    Co-Authors: Robe C Haddo


    The high electron affinity and the existence of radiating [pi]-orbitals when combined with simple ideas for the design of molecular Metals and superconductors led the authors to pursue conductivity and superconductivity in the Alkali Metal doped fullerenes. Further, the authors discuss the preparation and characterization of conducting and superconducting solids and films based on these materials and the current state of understanding within this field.