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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    European biophysics journal 10 (1983), S. 197-204 
    ISSN: 1432-1017
    Keywords: Ascorbic acid ; ESR ; Na+ ; K+
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract ESR investigations on lyophilized systems have shown that the signal at g = 2.005 can be explained by an interaction between Na+ or K+ and the anionic ascorbyl radical. The unpaired electron is probably localized near the C(4) region and is produced by a cleavage of an H atom belonging to a water molecule bound tightly to C(4). Experiments on aqueous samples revealed that ascorbic acid in its radical configuration and in its highest concentration exists only at physiological pH and temperature. An additional splitting is obtained by the ring formation between C(3) and C(6)-OH. The coupling constants of the triplets produced by the CH2-6 protons differ between ascorbic acid and isoascorbic acid. Thus, the ESR technique can be applied for an easy distinction between these two epimers.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    European biophysics journal 10 (1983), S. 205-210 
    ISSN: 1432-1017
    Keywords: Ascorbic acid ; Na+/K+-transport ; ESR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Ascorbic acid/isoascorbic acid are present as radicals at physiological pH with the unpaired electron located in the C(4) region. Since a distinction can be made between both types of radicals, the electron spin resonance technique can be used for discrimination between the epimers of vitamin C. The radical has a cyclic side-chain structure which is formed by the hydrogen bond C(3)-O− ... HO-C(6) (≈ 2.7 kJ) and which engulfs Na+ or K+ in the case of the ascorbyl or the isoascorbyl radical, respectively. The radicals Na-ASC and K-Iso-ASC are electroneutral. Red. glutathione affects both types of radicals by restoring the original electronic configuration at C(4) without changing the electroneutral bicyclic structure. In this way, the mobile carriers Na-ASC and K-Iso-ASC can transport Na+ and K+ across membranes. Its highest efficiency is around 37
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  • 3
    ISSN: 1432-0584
    Keywords: Acute myeloic leukemia ; Glutathione ; Ascorbic acid ; ESR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Electron spin resonance (ESR) spectra of lyophilized erythrocytes obtained from patients with acute myeloic leukemia (AML) show, in comparison to controls, a characteristic change especially in the low-field region of the spectrum concomitant with a reduction of the spin concentration. This effect can be simulated by addition of SH-containing substances (e.g. reduced glutathione or cysteine) to healthy erythrocytes. S-S containing compounds exhibit no effect. Since SH-containing substances can hardly permeate plasma membranes, the membrane surface seems to be defective in the case of “AML” erythrocytes. Furthermore, it can be concluded that the concentration of SH-containing substances, such as cysteine, is increased in the plasma of AML-patients, which could be confirmed by HPLC-measurements. In the case of a successful treatment of the patients with alexan, daunoblastin, and thioguanine the spin concentration increased again and the resulting ESR spectrum is very similar to the control spectrum. It should be pointed out, that the ascorbic acid concentration is very low in both plasma and erythrocytes of AML patients.
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  • 4
    ISSN: 1432-0584
    Keywords: ESR ; LeukÄmie ; AscorbinsÄure ; Antioxidanzien ; oxidierende Substanzen ; ESR ; Leukemia ; Ascorbic acid ; Antioxidants ; Oxidizing agents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Addition of ascorbic acid to native blood or to erythrocytes and leukocytes of healthy persons results in an ESR spectrum which is identical to the one obtained with blood or its fractions of leukemic patients. After an initial increase the spin concentration decreases at higher (〉 100 mM) concentrations of ascorbic acid. These findings confirm observations made thus far that cancerous tissue, finally, exhibits a lower spin concentration and a higher concentration of antioxidants than its corresponding healthy tissue. Application of oxidizing substances, such as KMnO4 or CuCl2, to erythrocytes either before or after administration of vitamin C compensates the effect of the latter substance depending, of course, on the concentration used. The effect produced by ascorbic acid on blood and its fractions seems to be unique since neither vitamin E or vitamin A or catechol and its amines noradrenaline, adrenaline, dopamine, and its precursor amino acid dopa, cytochrome c, FMN, NADH, Na2S2O4, ethylenglycol, glyceraldehyde, or tyrosine produce this effect. Ascorbic acid seems to play, thus, an important role in the balance of health and disease, as has been pointed out by Szent-Györgyi [16]. Its possible receptor(s) and its implication in the formation of cancer, or at least leukemia, will be discussed in detail elsewhere [9].
    Notes: Zusammenfassung Eine Zugabe von AscorbinsÄure zu nativem Blut oder zu Erythrozyten und Leukozyten von gesunden Personen ergibt ein ESR-Spektrum, das identisch zu dem ist, welches mit Blut oder seinen Fraktionen von LeukÄmie-Patienten erhalten wird. Nach einer anfÄnglichen Zunahme nimmt die Spin-Konzentration bei höheren (〉 100mM) AscorbinsÄure-Konzentrationen wieder ab. Diese Ergebnisse bestÄtigen bisherige Beobachtungen, wonach Krebsgewebe im fortgeschrittenen Stadium eine niedrigere Spin-Konzentration und eine grö\ere Konzentration an Antioxidanzien als das dazugehörige gesunde Gewebe besitzt. Eine Zugabe von oxidierenden Substanzen, wie z. B. KMnO4 oder CuCl2, zu Erythrozyten entweder vor oder nach Vitamin C Zugabe kompensiert den Effekt der letzteren Substanz, was natürlich von der gebrauchten Konzentration abhÄngt. Der durch AscorbinsÄure an Blut und seinen Fraktionen erzeugte Effekt scheint spezifisch zu sein, da weder Vitamin E nach Vitamin A oder Catechol und seine Amine Noradrenalin, Adrenalin, Dopamin und sein VorlÄufer, die AminosÄure Dopa, Cytochrom c, FMN, NADH, Na2S2O4, Äthylenglykol, Glyzeraldehyd oder Tyrosin diesen Effekt erzeugen.
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  • 5
    ISSN: 1432-0584
    Keywords: LeukÄmie ; Erythrozyten-Membran ; ESR ; Atomabsorption ; AscorbinsÄure ; Leukemia ; Erythrocyte ghosts ; ESR ; Atomic absorption ; Ascorbic acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary The effect of ascorbic acid on white ghosts of erythrocytes and plasma has been investigated by means of ESR spectroscopy. Since the spectra obtained are identical to the one obtained with leukemic blood, it is concluded that the receptor for vitamin C has to be searched for in membrane and plasma as well. Determination of Cu and Fe by means of atomic absorption spectroscopy revealed that both of the metals are also present in the membrane. In the case of copper, it must exist there as a protein which has not been identified yet. Oxidizing substances, such as KMnO4, reverse the effect produced by ascorbic acid.
    Notes: Zusammenfassung Die Wirkung von AscorbinsÄure auf Erythrozyten-Membran (white ghosts) und Plasma ist mittels der ESR-Spektroskopie untersucht worden. Da die erhaltenen Spektren identisch mit denen sind, die von leukÄmischem Blut erhalten wurden, wird angenommen, da\ der Rezeptor für Vitamin C sowohl in der Membran als auch im Plasma vorhanden sein mu\. Cu- und Fe-Bestimmungen mittels der Atomabsorptionsspektroskopie ergaben, da\ beide Metalle auch in der Membran vorhanden sind. Im Falle des Kupfers mu\ es dort als ein Protein vorliegen, das noch nicht identifiziert wurde. Oxidierende Substanzen, wie z. B. KMnO4, bewirken eine Umkehr des durch die AscorbinsÄure erzeugten Effektes.
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