Electrochemical reduction of monovalent cation complexes of macrocyclic ionophores. II. Valinomycin and macrotetrolide complexes

Hofmanová, A.; Koryta, J.; Březina, M.; Ryan, T. H.; Angelis, Karel J.

doi:10.1016/s0020-1693(00)95534-8

Cited by 34 publications

(16 citation statements)

References 19 publications

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“…[5][6][7][8][9][10][11][12][13][14][15][16] It should thus require a certain ion radius, ideally that of K þ (or larger). This idea has been supported by the known difference of three to four orders of magnitude between the stability constants of the K þ and Na þ complexes of valinomycin [17][18][19] and thus led to the conclusion that the structure of the latter complex must be different. 16 An even more different structure should thus be expected in the case of the proton complex (although, owing to the presence of small amounts of water, the proton is probably present in the form of hydroxonium ion H 3 O þ ).…”

Section: Discussionmentioning

confidence: 99%

“…In accord with this idea, valinomycin was found to be a selective K þ carrier, the stability of its complex with potassium ion being three to four orders of magnitude higher than that with sodium ion. [17][18][19] This is one of the reasons of interest whether valinomycin forms a stable complex with protons, the other being a possible role of valinomycin in the transmembrane transport of protons. We show in this study that such a complex is formed in an appropriate medium and in the presence of a sufficiently strong acid as a source of free protons.…”

Section: Introductionmentioning

confidence: 99%

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NMR evidence of a valinomycin–proton complex

2005

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In addition to the well-known complexes of valinomycin with alkali metal cations, an equimolar complex of the same compound with proton was found to be formed in nitrobenzene. Hydrogen bis(1,2-dicarbollylide) cobaltate (HDCC) was used as a proton source. According to NMR spectra, the complex formation is quantitative at proton/valinomycin molar ratios up to 1:1 but there is fast exchange of protons between coordinated and uncoordinated valinomycin molecules at lower ratios. 1 H and 13 C NMR spectra show a dramatic change in the valinomycin conformation during its coordination with protons, probably from a propeller-like to a bracelet-like form. As valinomycin is one of the well-known ion-carrying ionophores facilitating especially the K þ ion transport across a biological membrane, the existence of the valinomycin-proton complex could be important in biochemistry and biology. #

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

NMR evidence of a valinomycin–proton complex

2005

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“…Then, adequate volumes of 1 M NaCl and 1 M KCl were added into W1 and W2, respectively. The ionic composition in W1 was adjusted to 10 [16]. In this system, the concentration of anion in W1 (10 À3 M Â C ratio Cl À ) was same as that in W2 (10…”

Section: Preparation Of Blmsmentioning

confidence: 99%

Electrochemical Elucidation of the Facilitated Ion Transport Across a Bilayer Lipid Membrane in the Presence of Neutral Carrier Compounds

2010

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The ion transport facilitated by neutral carrier compounds (valinomycin, nonactin) has been investigated by cyclic voltammetry in the several electrolyte solutions (KF, KCl, KBr, KNO 3 , KSCN, KClO 4 ), and we demonstrated the effect of the counter anions on the facilitated transport of K þ from the viewpoint of electroneutrality. Voltammograms for the ion transport were generated at steady state and the current density between W1 and W2, j W1-W2, increased with the absolute value of the applied membrane potential, E W1-W2 . Then, the magnitude of j W1-W2 at a certain E W1-W2 increased with the hydrophobicity of the counter anion. It was proved that the logarithm of j j W1-W2 j at a certain E W1-W2 is almost proportional to the hydration energy of the counter anion. This indicates that not only K þ but also the counter anion distributes into the BLM. Therefore, the magnitude of j W1-W2 at a certain E W1-W2 increased with an increase of pH, because the hydroxide ion was served as a counter anion. Based on the variation of the zero-current potential in case of various asymmetrical ionic compositions, it is found that the amount of cation transport is much larger than that of anion transport.

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“…Fig. 8 shows the relation between the hydration energy of the alkali metal ions and the ion transfer current and that between the stability constant of the alkali metal ion-Val complex in the acetonitrile and the ion transfer current [24]. For the calculation, the hydration energies are used instead of the transfer energies from the aqueous phase to the BLM, since the transfer energies of the alkali metal ions from the aqueous to the BLM would be mainly attributed to the hydration energies because the exact values of their transfer energies cannot be evaluated.…”

Section: W1mentioning

confidence: 99%