Ion specific electrochemical behavior of macrotetrolides in membranes

Štefanac, Z.; Simon, W.

doi:10.1016/0026-265x(67)90014-8

Cited by 166 publications

(57 citation statements)

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“…The two peptide molecules in the asymmetric unit have similar conformations and have approximate threefold symmetry. Naturally occurring cyclic peptides such as enniatin (1)(2)(3) and valinomycin (4,5) are known to bind ions and mediate their transport across natural and prepared biological membranes; these peptides have been the subject of extensive investigations. The conformational changes that facilitate ion binding and transport can be studied in considerable detail by using x-ray crystallographic techniques, and such studies yield insight into the mechanism of ion binding and transport through membranes at the molecular level.…”

mentioning

confidence: 99%

Conformation of cyclo (-L-Pro-Gly-) ₃ and its Ca ²⁺ and Mg ²⁺ complexes

Kartha

Varughese

Aimoto

1982

Proc. Natl. Acad. Sci. U.S.A.

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The synthetic hexapeptide cyclo(-L-Pro-Gly-)3 is an ionophore that shows interesting conformational changes upon binding metal ions. X-ray crystallographic studies of this peptide show that when it is crystallized from an ethanol/ethyl acetate mixture the ring takes up an asymmetric conformation containing one cis peptide bond. In crystals of a Ca"s complex, the cation is sandwiched between two peptide molecules that differ markedly in conformation. However, both exhibit threefold symmetric forms, with all six peptide bonds in.the molecule occurring in the usual trans conformation. The Ca"' is octahedrally surrounded by six glycyl carbonyl oxygens from the two peptides at an average distance of 2.26 A and can easily be released by the disruption-of the peptide sandwich. In the magnesium complex, the peptide forms a 1:1 complex with the ion. The Mg2 is octahedrally coordinated to three glycyl carbonyls and three water oxygens. The average coordination distance between magnesium and the peptide oxygens is 2.03 A and that between magnesium and water oxygen-is 2.11 A. The two peptide molecules in the asymmetric unit have similar conformations and have approximate threefold symmetry. Naturally occurring cyclic peptides such as enniatin (1-3) and valinomycin (4, 5) are known to bind ions and mediate their transport across natural and prepared biological membranes; these peptides have been the subject of extensive investigations. The conformational changes that facilitate ion binding and transport can be studied in considerable detail by using x-ray crystallographic techniques, and such studies yield insight into the mechanism of ion binding and transport through membranes at the molecular level. These studies and. the interpretation of-the results are much simplified by the use of simple model peptides that mimic these properties and can easily be synthesized in the laboratory. One such synthetic peptide that mimics the ion binding properties of antamanide (6) and enniatin is. the hexapeptide cyclo(-L-Pro-Gly-)3 [hereinafter denoted (PC)3], which has been extensively studied by Blout and co-workers by spectroscopic and computed potential energy techniques (7,8). From their studies they concluded that (PG)3 conformation varies significantly writh the nature of the medium. In nonpolar medium as well as when forming complexes with cations, (PG)3 takes up a threefold symmetric conformation, and in polar solvents this changes to an asymmetric conformation with one ofthe peptide bonds in the cis configuration. Even though crystallographic results of a few cyclic hexapeptides have been reported, most of these contain two f-turns, with the peptide rings having at least an approximate twofold or inversion symmetry. The threefold nature of the chemical sequence of (PG)3 and the existence of alternating proline residues exert conformational restrictions that make the usual dou- ble 3-turn structure with intramolecular hydrogen bonds impossible for this hexapeptide. We report here the conformational features of this pep...

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mentioning

confidence: 99%

Conformation of cyclo (-L-Pro-Gly-) ₃ and its Ca ²⁺ and Mg ²⁺ complexes

Kartha

Varughese

Aimoto

1982

Proc. Natl. Acad. Sci. U.S.A.

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“…A wideranging research was started after this not only in the field of precipitate-based ion-selective electrodes but also on the application of complexing agents [12] and other materials to prepare electrodes. Ion transport was generally accepted as the source of electrode potential, so much so that complexing ligands were called 'ion carriers'.…”

Section: Experiments To Study the Establishment Of The Electrode Potementioning

confidence: 99%

“…LaF3, AgI, Ag2S etc. ), and valinomycin-based [12] and bis-crownether-based [ 181 electrodes. It is known that after immersion into a solution, the solid phase is covered by an adhering layer of a thickness of about 1 pm.…”

Section: Kinetic Studiesmentioning

confidence: 99%

Ion‐selective electrodes – analogies and conclusions

Püngor

1996

Electroanalysis

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The author investigated the working mechanism of ion-selective electrodes. The contradictions of theories deduced from so-called analogous phenomena were discussed in detail. Based on experiments made by his research group he came to the conclusion that only the surface (the active groups located there) takes part in the potential-determining reaction, and the bulk resistance of the membrane has a role only in the selection of the instrument used for potential measurement.

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“…In 1967, Ross described the first membrane electrode based on a liquid ion exchanger [2] and Bloch and co-workers introduced the first ionophore-based solvent polymeric membrane based on PVC [3], a matrix still widely used today. At about the same time, Stefanac and Simon discovered that antibiotics inducing selective-ion transport through biological membranes also generate a selective potentiometric response in liquid membranes [4]. Finally, this was also the time of birth of host-guest chemistry [5,6], which later played an important role in developing novel selective ionophores.…”

Section: Introduction -The Status 25 Years Agomentioning

confidence: 99%

The new wave of ion-selective electrodes

Pretsch

2007

TrAC Trends in Analytical Chemistry

141

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During the last decade, the capabilities of potentiometric analysis have changed fundamentally in that the lower limit of detection (LOD) of ion-selective electrodes (ISEs) has improved by a factor of up to one million and the discrimination factor of interferences from ions by up to one billion. These spectacular improvements are related to the control of ion fluxes through the ion-selective membrane. Nowadays, ISEs can be used for trace measurements in environmental samples. However, by reducing the volume of the samples, the LOD in terms of the amount of analytes has been reduced to the attomole range. This is promising for bioanalysis using metal nanoparticle labels. Other recent progress includes the excellent fundamental understanding of the working mechanism, the introduction of a novel kind of calibration procedure that reduces the demands on signal stability and reproducibility, and the advent of pulsed amperometric methods.

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Ion specific electrochemical behavior of macrotetrolides in membranes

Cited by 166 publications

References 7 publications

Conformation of cyclo (-L-Pro-Gly-) ₃ and its Ca ²⁺ and Mg ²⁺ complexes

Conformation of cyclo (-L-Pro-Gly-) ₃ and its Ca ²⁺ and Mg ²⁺ complexes

Ion‐selective electrodes – analogies and conclusions

The new wave of ion-selective electrodes

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Ion specific electrochemical behavior of macrotetrolides in membranes

Cited by 166 publications

References 7 publications

Conformation of cyclo (-L-Pro-Gly-) 3 and its Ca 2+ and Mg 2+ complexes

Conformation of cyclo (-L-Pro-Gly-) 3 and its Ca 2+ and Mg 2+ complexes

Ion‐selective electrodes – analogies and conclusions

The new wave of ion-selective electrodes

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Conformation of cyclo (-L-Pro-Gly-) ₃ and its Ca ²⁺ and Mg ²⁺ complexes

Conformation of cyclo (-L-Pro-Gly-) ₃ and its Ca ²⁺ and Mg ²⁺ complexes