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  • 1
    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.
    Type of Medium: Electronic Resource
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  • 2
    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.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1017
    Keywords: Stacking ; selfassociation ; NMR ; Isodesmic Model ; Enthalpy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The selfassociation of N6,N9-dimethyladenine and N6-dimethyl-N9-ethyladenine has been studied by means of NMR technique. The thermodynamic quantities have been calculated using an isodesmic NMR model with three NMR parameters (the monomer shift δM and two complex shifts δ 2 and δ 3). The dependence of the thermodynamic quantities on the NMR parameters is discussed. Special attention is given to the determination of δ M and its temperature dependence. Calculations with δ 3=2·δ 2 and δ M taken independently of temperature result in an average entropy δ S =−17.9±1.8 e.u. for N6,N9-dimethyladenine and δ S =−16.7±1.7 e.u. for N6-dimethyl-N9-ethyladenine and in an average enthalpy δH=−7.2±0.6 kcal· mol−1 for both substances investigated.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    European biophysics journal 1 (1975), S. 311-318 
    ISSN: 1432-1017
    Keywords: Stacking ; Selfassociation ; NMR ; Nucleobases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The selfassociation of various purine- and pyrimidine-derivatives in D2O has been studied by means of NMR technique. The thermodynamic quantities have been calculated using an isodesmic NMR model. Among the nucleobases investigated, the adenine-derivatives were found to be most suitable for quantitative determination. A comparison of methylated adenine-derivatives and the pH-dependence of the selfassociation lead to the conclusion, that the stacking associates are stabilized by special van der Waals interactions based, essentially, on the polarizability of the π-electron-system of the associated molecules.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    European biophysics journal 4 (1978), S. 327-335 
    ISSN: 1432-1017
    Keywords: Stacking ; Solvent-mixtures ; 6-methylpurine ; Self-association
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The stacking interaction between nucleic acid bases has been investigated by the determination of the self-association of 6-methylpurine in various mixtures of water and nonaqueous solvents in order to elucidate the solvent effect. The parameters of stacking association as well as of local solvent-solute interactions have been measured by means of NMR technique. The influences of local hydration and of solvent-solvent interactions on the stacking ability are discussed.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    European biophysics journal 1 (1975), S. 319-328 
    ISSN: 1432-1017
    Keywords: Sexual Hormones ; Nucleobases ; NMR ; Stacking ; Enthalpies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The mixed association of testosterone-sulfate and estradiol-sulfate with several derivatives of nucleobases in D2O has been investigated by means of nuclear magnetic resonance spectroscopy. From, the differences among the chemical shifts of the hormone-protons it is concluded, that the nucleobases in the complexes are located above the center of the steroid molecule. The Β-side of the steroid which is characterized by the axial methyl-groups is directed towards the bases. The enthalpies of mixed association of the hormones with a certain nucleobase are of the same order of magnitude as the enthalpy of selfassociation of this nucleobase (Schimmack et al., to be published). It is suggested that the complexes are stabilized by van-der-Waals forces. This stacking-like interaction is not specific for the male or female sex hormones: no qualitative or quantitative differences have been observed among the complexes of the two hormone-sulfates with the nucleobases.
    Type of Medium: Electronic Resource
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