• Title/Summary/Keyword: Ionophores

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Lipid Peroxidation revisited : are Oxidized Fatty Acide cell's Own Calcium-specific Ionophores Produced by Higher Organisms\ulcorner (과산화지질에 대한 재고찰 : 지방산 산화물은 고등생물이 만들어내는 칼슘-수송체인가\ulcorner)

  • 송영순
    • YAKHAK HOEJI
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    • v.35 no.1
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    • pp.45-60
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    • 1991
  • lonophores, uniquely, create specific pathways of ion permeability in model and cell membranes. Calcium-transporting ionophores of microbiological origin, such as A23187 and ionomycin, have been used as experimental tools to elucidate the physiological role of calcium as a second messenger in many cell types. These ionophores are believed to bypass the initial ligand-receptor step in the activation of cells by increasing membrane permeability to calcium. In this report, we shall discuss several naturally occurring substances that share some properties of calcium-ionophores, primarily concentrating on oxidized fatty acids. We have previously demonstrated that oxidized linoteic and arachidonic acids, obtained either by lipoxygenase catalysis or nonenzymatic processes, significantly promote calcium translocation in a two-phase partition model and modulate calcium-transporting function in the isolated sarcoplasmic reticulum vesicles obtained from mammalian hearts. We have also confirmed that calcium-ionophoric properties are due not to their general amphiphilic nature of certain lipids, but to distinct structural characteristics. Although there are some skeptical views on the occurrence of ionophores in higher organisms, increasing evidence suggests that membrane lipids or their derivatives may serve as physiological calcium-ionophores. Abnormal accumulation of lipid peroxidation products(particularly end products), however, may be associated with the general oxidative damages as seen in many pathological conditions.

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The Potentiometric Performances of the Cation Selective Electrodes based on Tetracycline and Chemically Modified Tetracycline

  • Kang, Sang-Hyuk;Rhee, In-Sook;Paeng, Ki-Jung
    • Journal of Electrochemical Science and Technology
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    • v.2 no.3
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    • pp.143-145
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    • 2011
  • Metal-binding antibiotics are very attractive choices as cation selective ionophores. The ability of tetracycline (TC) antibiotics to bind to metal ions has obtained much attention. TCs exhibit the potentiometric performance changes for various cations dependant on several experiment conditions. In this report, we investigated the potentiometric performance changes of TC as the modification of TC's possible metal binding site. We found that the selectivity alter with the blocking main binding site of ionophores for cations. And, additionally it is possible to control the selectivity of sensors with chemical modification of ionophores.

Lithium Ion Selective Electrode Based on a Synthetic Neutural Carrier (중성운반체를 이용한 리튬이온 선택 전극)

  • Kim, Jae Sang
    • Analytical Science and Technology
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    • v.5 no.1
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    • pp.33-39
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    • 1992
  • THF-based crown-4 of 16-membered rings having tetrahydrofuran unit was synthesized by an acid-catalyzed condensation of furan and acetone followed by hydrogenation in an effort to obtain highly elective ionophores for lithium ions. The new ionophore was compared with previously reported ionophores under similar measurement conditions with the same plasticizer, tris(2-ethylhexyl) phosphate in poly(vinyl chloride)(PVC) membrane electrodes. Separate solution method was used to determine relative selectivity coefficients for the electrode. The selectivity coefficients($K_{LiM}^{POT}$) of lithium over ammonium, alkali and alkaline earth metal ions go from about $2.4{\times}10^{-1}$ to $2.3{\times}10^{-4}$ to working range and pH dependence have also been studied.

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Theoretical Study of Trioxane Derivatives as Amphi-ionophores: Importance of Charge-Dipolar Moiety Orientation

  • Cho, Seung Joo
    • Bulletin of the Korean Chemical Society
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    • v.35 no.9
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    • pp.2723-2725
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    • 2014
  • Recently we have reported a novel class of anion receptors which are based on 2n-crown-n topology. Trioxane derivatives are capable of anion sensing through pure aliphatic C-H hydrogen bonding. In this work, we highlight another interesting property, i.e., they can also recognize cations as normal crown ethers (3n-crown-n topology). Since the same functional moiety can recognize anions and cations, these coronands are predicted to be amphi-ionophores. However, we could not detect cations even in the gas phase. Considering trioxane is analogous to [$1_6$]starand, this was rather counter-intuitive. The calculation results show that these coronands can detect alkali metals with very low affinity. The low affinity toward cations should be responsible for this failure of experimental detection. With careful theoretical study, we found that this low affinity toward cations could be explained by the unfavorable charge-dipolar moiety orientations as proposed by Cui et al. As in the case of [$1_6$]starand, this is an example that underscores the importance of charge-dipolar moiety orientation in supramolecular interactions.