Tetrapyrrolic compounds as hosts for binding of halides and alkali metal cations

2009 ◽  
Vol 13 (11) ◽  
pp. 1148-1158 ◽  
Author(s):  
Mikalai M. Kruk ◽  
Aleksander S. Starukhin ◽  
Nugzar Zh. Mamardashvili ◽  
Galina M. Mamardashvili ◽  
Yulia B. Ivanova ◽  
...  
Keyword(s):  
Alkali Metal ◽  
Pyridine Ring ◽  
Alkali Metal Cation ◽  
Metal Cations ◽  
Cation Binding ◽  
Halide Ions ◽  
Alkali Metal Cations ◽  
Cation Complexation ◽  
Iodide Ions ◽  
Binding Isotherms

In this paper the binding of halides and alkali metal cations with porphyrin hosts is reported. The halide ions are complexed with diprotonated porphyrin macrocycle with high affinity and stable complexes of 1:1 and 1:2 structures with halide ions are formed. Strong (up to 300 times) quenching of the porphyrin fluorescence has been found upon the titration of porphyrin solutions with iodide ions. It was established that both static quenching upon formation of the non-fluorescent complex and dynamic diffusion-controlled quenching took place. It is shown that the halide ions binding isotherms can be linearized with double-logarithmic plots. The alkali metal cations are trapped with mono-meso-arylporphyrins containing a conformationally mobile complexing polyether fragment on the benzene ring with a terminal pyridine ring. The alkali metal cation binding constant depends on the polyether chain length. The five-membered (n = 5) polyether chain provides very high binding selectivity for potassium over lithium or sodium. The potassium complexation constants 3.6 × 105 and 7.2 × 104 M-1 have been obtained for Zn 2+ complex and diprotonated porphyrin, respectively. For signaling of the alkali cation complexation, it is proposed to use the binding between the terminal pyridine ring with either the Lewis acidic site (chelated Zn 2+ ion) or the diprotonated macrocycle core ( H 4 P 2+) acting as salt bridging site.

scholarly journals Discrimination between Alkali Metal Cations by Yeast

1967 ◽  
Vol 50 (4) ◽  
pp. 967-988 ◽  
Author(s):  
W. McD. Armstrong ◽  
A. Rothstein
Keyword(s):  
Alkali Metal ◽  
Competitive Inhibition ◽  
Metal Cations ◽  
Competitive Inhibitor ◽  
Cation Binding ◽  
Alkali Metal Cations ◽  
System A ◽  
Low Concentrations ◽  
K Transport ◽  
Noncompetitive Inhibitors

K+ is a competitive inhibitor of the uptake of the other alkali metal cations by yeast. Rb+ is a competitive inhibitor of K+ uptake, but Li+, Na+, and Cs+ act like H+. At relatively low concentrations they behave as apparent noncompetitive inhibitors of K+ transport, but the inhibition is incomplete. At higher concentrations they inhibit the remaining K+ transport competitively. Ca++ and Mg++ in relatively low concentrations partially inhibit K+ transport in an apparently noncompetitive manner although their affinity for the transport site is very low. In each case, in concentrations that produce "noncompetitive" inhibition, very little of the inhibiting cation is transported into the cell. Competitive inhibition is accompanied by appreciable uptake of the inhibiting cation. The apparently noncompetitive effect of other cations is reversed by K+ concentrations much higher than those necessary to essentially "saturate" the transport system. A model is proposed which can account for the inhibition kinetics. This model is based on two cation-binding sites for which cations compete, a carrier or transporting site, and a second nontransporting (modifier) site with a different array of affinities for cations. The association of certain cations with the modifier site leads to a reduction in the turnover of the carrier, the degree of reduction depending on the cation bound to the modifier site and on the cation being transported.

Neutral glycoconjugated amide-based calix[4]arenes: complexation of alkali metal cations in water

2018 ◽  
Vol 16 (6) ◽  
pp. 904-912 ◽  
Author(s):  
Nikola Cindro ◽  
Josip Požar ◽  
Dajana Barišić ◽  
Nikola Bregović ◽  
Katarina Pičuljan ◽  
...  
Keyword(s):  
Alkali Metal ◽  
Aqueous Solutions ◽  
Binding Sites ◽  
Metal Cations ◽  
Cation Binding ◽  
Water Soluble ◽  
Alkali Metal Cations ◽  
Complexation Reactions

Novel water-soluble calix[4]arene glycoconjugates with efficient cation-binding sites were synthesized and their complexation reactions in methanol and aqueous solutions were studied.

scholarly journals The effect of the alkali metal cation on the electrocatalytic oxidation of formate on platinum

RSC Advances ◽  
2014 ◽  
Vol 4 (29) ◽  
pp. 15271-15275 ◽  
Author(s):  
Bruno A. F. Previdello ◽  
Eduardo G. Machado ◽  
Hamilton Varela
Keyword(s):  
Alkali Metal ◽  
Metal Cation ◽  
Electrocatalytic Oxidation ◽  
Alkali Metal Cation ◽  
Metal Cations ◽  
Alkali Metal Cations ◽  
Non Covalent Interactions ◽  
Electro Oxidation ◽  
Covalent Interactions

Non-covalent interactions between hydrated alkali metal cations and oxygenated species on platinum considerably impact the mechanism of formate electro-oxidation.

Crystal Structures of Titanium(III) Bis(acetylide) Tweezer Complexes with Alkali Metal Cations

1997 ◽  
Vol 62 (9) ◽  
pp. 1446-1456 ◽  
Author(s):  
Jörg Hiller ◽  
Vojtech Varga ◽  
Ulf Thewalt ◽  
Karel Mach
Keyword(s):  
Alkali Metal ◽  
Crystal Structures ◽  
Metal Cation ◽  
Alkali Metal Cation ◽  
Metal Cations ◽  
Polymer Chains ◽  
Alkali Metal Cations ◽  
Bonding Interaction ◽  
Intermolecular Bonding ◽  
Trimethylsilyl Groups

Crystal structures of the Ti(III) tweezer complexes [(C5HMe4)2Ti(σ-C≡CSiMe3)2]-[Li(THF)2]+ (2a), [(C5HMe4)2Ti(σ-C≡CSiMe3)2]-Na+ (3) and [(C5HMe4)2Ti(σ-C≡CSiMe3)2]-Cs+ (5) have been determined. In all of them the alkali metal cation is placed away from the Ti-Cα1-Cα2 plane at the distance: Li+ 0.511 Å, Na+ 1.023 Å and Cs+ 0.521 Å. The reason for the deviation of Li+ in 2a is the asymmetrical orientation of the THF ligands in the [Li(THF)2]+ cation with respect to the Ti-Cα1-Cα2 plane, which seems to release the steric congestion between the THF ligands and the trimethylsilyl groups. In 3 and 5, the molecules form polymer chains with a weak intermolecular bonding interaction between the cations and one of the C5HMe4 ligands of the neighbouring molecule in a sandwich manner.

scholarly journals Cation and anion sequences in dark-adapted Balanus photoreceptor.

1977 ◽  
Vol 70 (4) ◽  
pp. 531-543 ◽  
Author(s):  
H M Brown ◽  
J H Saunders
Keyword(s):  
Membrane Potential ◽  
Alkali Metal ◽  
Resting State ◽  
Alkali Metal Cation ◽  
Membrane Conductance ◽  
Metal Cations ◽  
Alkali Metal Cations ◽  
Inward Current ◽  
Current Pulses ◽  
Cation Permeability

Anion and cation permeabilities in dark-adapted Balanus photoreceptors were determined by comparing changes in the membrane potential in response to replacement of the dominant anion (Cl-) or cation (Na+) by test anions or cations in the superfusing solution. The anion permeability sequence obtained was PI greater than PSO4 greater than PBr greater than PCl greater than Pisethionate greater than Pmethanesulfonate. Gluconate, glucuronate, and glutamate generally appeared more permeable and propionate less permeable than Cl-. The alkali-metal cation permeability sequence obtained was PK greater than PRb greater than PCx greater than PNa approximately PLi. This corresponds to Eisenman's IV which is the same sequencethat has been obtained for other classes of nerve cells in the resting state. The values obtained for the permeability ratios of the alkali-metal cations are considered to be minimal. The membrane conductance measured by passing inward current pulses in the different test cations followed the sequence, GK greater than GRb greater than GCs greater than GNa greater than GLi. The conductance ratios obtained for a full substitution of the test cation agreed quite well with permeability ratios for all the alkali-metal cations except K+ which was generally higher.

Study of photocatalytic reaction of methanol with water over Rh-, and Pd-loaded TiO2 catalysts. The role of added alkali metal cations

1986 ◽  
Vol 64 (9) ◽  
pp. 1795-1799 ◽  
Author(s):  
Shuichi Naito
Keyword(s):  
Alkali Metal ◽  
Metal Cation ◽  
Methyl Formate ◽  
Alkali Metal Cation ◽  
Metal Cations ◽  
Photocatalytic Reaction ◽  
Product Selectivity ◽  
Alkali Metal Cations ◽  
Selectivity Change

The product selectivity of the photocatalytic reaction of methanol with water is changed drastically by the addition of alkali metal cations to Rh- and Pd-loaded TiO2 catalysts. Over alkali metal cation free catalysts, the main products are 1:1 ratio of H2 and dimethoxymethane, which is replaced with H2, methyl formate, and CO2 over alkali metal cation added catalysts. The role of added alkali metal cations is the stabilization of the reaction intermediate as adsorbed formate instead of adsorbed formaldehyde, which causes the selectivity change from dimethoxymethane to methyl formate.

scholarly journals Alkali Metal Cation Transport and Homeostasis in Yeasts

2010 ◽  
Vol 74 (1) ◽  
pp. 95-120 ◽  
Author(s):  
Joaquín Ariño ◽  
José Ramos ◽  
Hana Sychrová
Keyword(s):  
Plasma Membrane ◽  
Alkali Metal ◽  
Metal Cation ◽  
Higher Plants ◽  
Alkali Metal Cation ◽  
Metal Cations ◽  
Cation Transport ◽  
Transport Processes ◽  
Alkali Metal Cations ◽  
Yeast Saccharomyces Cerevisiae

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.

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