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  • 1
    ISSN: 0899-0042
    Keywords: lipoic acid ; reduction ; dihydrolipoamide dehydrogenase ; antioxidant ; enantiomers ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: For the antioxidant effect of lipoic acid, reduction to dihydrolipoic acid is considered to be important. Dihydrolipoamide dehydrogenase (LipHD) preferentially reduces R-lipoic acid and in a subsequent reaction, the R-dihydrolipoic acid formed may non-enzymatically reduce S-lipoic acid. Using circular dichroism (CD) spectroscopy, the second order rate constant of the latter reaction was determined (k2 = 15 M-1 sec-1). In vitro, it was found that S-lipoic acid is reduced by LipDH using R-lipoic acid as a catalyst. The non-enzymatic dithiol-disulfide reaction leads to synergistic reduction of the enantiomers which can explain the higher antioxidant activity of racemic lipoic acid found in vivo (Maitra et al. Biochem. Biophys. Res. Commun. 221:422-429, 1996) in comparison to the enantiomers. Lipoic acid is therapeutically active in several diseases via antioxidant activity. These findings suggest that racemic lipoic acid can be therapeutically more active than the separate enantiomers. Chirality 9:362-366, 1997. © 1997 Wiley-Liss, Inc.
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 105 (1972), S. 2825-2840 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 1.3-Dipolar Cycloadditions, 68. Additions of Nitrile Oxides to CN-Multiple BondsAzomethines with aromatic or aliphatic substituents (aldimines, ketimines) react with benzonitrile oxide to give Δ2-1.2.4-oxadiazolines in good yields (19 examples). 2.4.6-Trimethyl-benzonitrile oxide combines with phenyl isocyanate to give the 1.2.4-oxadiazolin-5-one 25. The cycloaddition of nitrile oxides to nitriles leads to 1.2.4-oxadiazoles (14 examples). Here the in situ technique in generation of the nitrile oxide is advantageous, because nitriles are dipolarophiles of lower activity than azomethines. Aromatic nitriles are sufficiently active as are aliphatic nitriles with electron-attracting substituents.
    Notes: Aromatisch und aliphatisch substituierte Azomethine (Aldimine, Ketimine) treten mit Benzonitriloxid zu Δ2-1.2.4-Oxadiazolinen in guter Ausbeute zusammen (19 Beispiele). 2.4.6-Trimethyl-benzonitriloxid vereinigt sich mit Phenylisocyanat zum 1.2.4-Oxadiazolinon-(5) 25. Für die zu 1.2.4-Oxadiazolen führende Addition von Nitriloxiden an Nitrile (14 Beispiele) bewährt sich die in situ-Arbeitsweise; Nitrile sind schwächere Dipolarophile als Azomethine. Aromatische Nitrile sowie elektronenanziehend substituierte aliphatische Nitrile sind genügend aktiv.
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 106 (1973), S. 3312-3344 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 1,3-Dipolar Cycloadditions, 73. Relative Dipolarophile Activities in Cycloadditions of Benzonitrile OxideThe cornpetition of pairs of dipolarophiles for benzonitrile oxide, liberated in situ from benzohydroximoyl chloride (4), allows evaluation of the relative addition constants of 39 dipolarophiles which cover a range of four powers of ten. Benzonitrile oxide belongs to the type of 1,3-dipoles which react faster both with electron-deficient and electron-rich multiple bonds than with common alkenes and alkynes. Combination of these data with the known orientations provides the partial rate factors for the two directions of cycloaddition. The additivity of substituent contributions to the free energy of activation is only fulfilled to a first approximation.  -  The specific dipolarophile scale of benzonitrile oxide, as well as the orientation phenomena, are discussed in the light of the new MO perturbation treatments of Sustmann and Houk. The dipolarophile activity sequence of benzonitrile oxide is compared with those of diphenylnitrilimine and N-methyl-C-phenylnitrone.
    Notes: Die Konkurrenz von Dipolarophilen-Paaren um Benzonitriloxid,. In situ aus Benzohydroximoylchlorid (4) freigesetzt, ergab die sich über 4 Zehnerpotenzen erstreckenden relativen Additionskonstanten von 39 Dipolarophilen. Benzonitriloxid gehört zu den 1,3-Dipolen, die sowohl mit elektronen-armen als auch mit elektronen-reichen Mehrfachbindungen rascher reagieren als mit gewöhnlichen Alkenen und Alkinen. Die Kombination mit den bekannten Orientierungsverhältnissen erbrachte partielle Geschwindigkeitskonstanten der beiden Additionsrichtungen. Die Additivität der Substituenten-Beiträge zur freien Aktivierungsenergie ist nur näherungsweise erfüllt.  -  Die spezifische Dipolarophilen-Skala des Benzonitriloxids sowie die Orientierungsphänomene werden im Lichte neuer MO-störungstheoretischer Behandlungen von Sustmann und Houk diskutiert. Die Aktivitätssequenz wird mit denjenigen des Diphenylnitrilimins und des N-Methyl-C-phenylnitrons verglichen.
    Additional Material: 8 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 106 (1973), S. 3258-3274 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 1,3-Dipolar Cycloadditions, 70. Additions of Benzonitrile Oxide to Olefinic and Acetylenic DipolarophilesBenzonitrile oxide (2) forms with monosubstituted ethylenes and acetylenes 2-isoxazolines (3-10) and isoxazoles (29, 42) substituted in the 5-position. β-Substituted styrenes yield a mixture of two possible orientation isomers (17/18, 19/20), except β-pyrrolidinostyrene, which produces only 3,4-diphenyl-5-pyrrolidino-2-isoxazoline (22). In other enamines, too, the amino function dictates this direction of addition notwithstanding steric effects. The stereospecificity of the cycloaddition has been shown by the reactions of the cis-trans-isomeric 2-butenes and stilbenes (13-16). Besides cyclopentene the less reactive cyclohexene could be combined with benzonitrile oxide (36, 37). The labile bicyclic primary adduct of cyclooctatetraene (38) undergoes electrocyclic ring closure to form the tricyclic product 39.
    Notes: Benzonitriloxid (2) bildet mit monosubstituierten Äthylenen und Acetylenen 2-Isoxazoline (3-10) und Isoxazole (29, 42), bei denen der Rest in der 5-Position erscheint. Ein Gemisch der beiden möglichen Orientierungsisomeren (17/18, 19/20) geht aus den Additionen an β-substituierte Styrole hervor. Abweichend verhielt sich β-Pyrrolidinostyrol, aus dem mit Benzonitriloxid nur 3,4-Diphenyl-5-pyrrolidino-2-isoxazolin (22) entsteht. Auch bei anderen Enaminen diktiert die Aminfunktion ungeachtet sterischer Effekte diese Additionsrichtung. Die Stereospezifität der Cycloaddition wurde an den cis-trans-isomeren 2-Butenen und Stilbenen dargetan (13-16). Neben Cyclopenten wurde auch das reaktionsträgere Cyclohexen zur Reaktion gebracht (36, 37). Das labile bicyclische Primäraddukt des Cyclooctatetraens (38) erleidet einen elektrocyclischen Ringschluß zum tricyclischen Produkt 39.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Cell Biochemistry and Function 5 (1987), S. 143-147 
    ISSN: 0263-6484
    Keywords: Radioligand binding ; HeLa cells ; beta-adrenergic receptor ; cell morphology ; non-specific binding ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Harvesting of plated growing HeLa cells, followed by incubation of these cells without any addition at 37°C was found to cause changes in the cell shape. This phenomenon is accompanied by a diminished binding of the beta-adrenergic antagonist [3H]-dihydroalprenolol and the alpha-adrenergic antagonist phentolamine to a binding compartment not representing beta-adrenergic receptors. These binding sites have a high affinity for hydrophobic agents and most probably represent lipophilic structures in the cellular membrane. Changes in the cell shape obviously cause alterations in the physical properties of the plasma membrane. This might lead to misinterpretations of the results from experiments in which the redistribution of beta-adrenergic receptors is followed during incubation with agonists, as receptor occupation with subsequent receptor redistribution is possibly accompanied by effects on the membrane microviscosity.It is concluded that investigations performed in order to follow physiological events like receptor redistribution and desensitization processes, may be obfuscated by changes in the normal physical state of the living cells.
    Additional Material: 5 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 561 (1949), S. 165-173 
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 7
    ISSN: 1434-193X
    Keywords: Isoquinolinium N-arylimides ; Azomethine imines ; Cycloadditions ; Heterocycles ; 1,3-Dipoles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The red isoquinolinium N-arylimides 19-23 are azomethine imines of which the C=N bond is part of an aromatic ring. The N-(4-nitrophenyl)imide 22 and the N-(2-pyridyl)imide 23 were obtained crystalline; in solution the latter equilibrates with the hexahydrotetrazine 24 as its dimer. The N-phenylimide 19 is not stable; an isolated solid appears to be a tetramer. Generated by deprotonation of 11-13, the N-arylimides 19-21 undergo in situ cycloadditions to carbon disulfide, phenyl isocyanate, phenyl isothiocyanate, and diphenylketene. The storable CS2 adduct 29 offers a neutral source of theN-phenylimide 19, since a cycloreversion equilibrium is established in solution.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 59 (1995), S. 219-222 
    ISSN: 0730-2312
    Keywords: Detection molecular markers ; ovarian cancer ; prevention ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: More than 90% of epithelial ovarian cancers arise from single cells. Malignant transformation can be associated with a number of molecular alterations including upregulation of tyrosine kinases and phosphatases, physiologic activation of ras, mutation of p53, amplification of myc, and increased activity of matrix metalloproteinases 2 and 9. Proliferation of transformed epithelial cells can be enhanced through the persistence of autocrine growth stimulation by TGF-α, loss of autocrine growth inhibition by TGF-β, as well as paracrine growth stimulation by macrophage derived cytokines and OCAF, a novel lyso-phospholipid. Ascites tumor cells retain responsiveness to growth inhibition by TGF-β which induces apoptosis in malignant ovarian epithelial cells, but not in normal ovarian surface epithelium.Proliferation of surface epithelial cells following ovulation my contribute to the pathogenesis of ovarian cancer. Use of oral contraceptives that suppress evulation has been associated with reduced risk of ovarian cancer in later life. Retinoids also deserve further evaluation for chemoprevention. Treatement with fenretinide was associated with decreased incidence of ovarian cancer. Additive or synergistic inhibition of ovarian tumor cell proliferation has been observed with TGF-β in combination with all-trans-retinoic acid.Early detection of ovarian cancer could improve survival. Transvaginal sonography (TVS) and serum markers such as CA-125 have been evaluated in multiple clinical trials. The former lacks adequate specificity, whereas the latter is not sufficiently sensitive. Use of multiple serum markers can improve sensitivity. A combination of CA-125, M-CSF and OVX-1 has detected 〉 95% of Stage I ovarian cancers. If similar results are obtained with different data sets, multiple serum markers could be used to trigger the performance of TVS, providing a potentially cost effective screening strategy. Prospective trials will be required to demonstrate that screening for early stage ovarian actually impacts on survival.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 131 (1987), S. 36-42 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Treatment of murine peritoneal macrophages for 30 min with lipopolysaccharide (LPS) resulted in a transient increase in c-fos proto-oncogene mRNA levels (Introna et al., 1986). After 2 h from the initial treatment, c-fos mRNA could no longer be detected and its expression could not be restimulated either by LPS or by other signals including colony stimulating factor-1 (CSF-1) and phorbol myristate acetate (PMA), both of which are able to induce expression of the c-fos gene in unstimulated macrophages. When LPS was removed after an initial 30 min incubation, responsiveness to a second exposure to LPS began to reappear after 3 h and was completely restored by 20 h. The same pattern of desensitization of c-fos induction was observed when CSF-1 stimulated macrophages were subsequently exposed to LPS. The loss of sensitivity to PMA following pretreatment with LPS was selective for c-fos expression as LPS treated macrophages remained responsive to PMA with respect to the ability to stimulate secretion of H2O2. The mechanism of desensitization was localized, at least in part, at the level of transcription as demonstrated by analysis of c-fos transcripts in nuclei isolated from macrophages pretreated and restimulated with LPS.
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 99 (1987), S. 1242-1250 
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Die moderne NMR-Spektroskopie, insbesondere die zweidimensionalen Meßmethoden, eröffnen auch für die Strukturaufklärung von Organolithium-Verbindungen neue Wege, wobei das Zusammenspiel der 1H-, 13C- und 6(7)Li-NMR-Spektroskopie besonders nützlich ist. So ermöglichen homo- und heteronucleare Verschiebungskorrelationen die komplette Zuordnung der 1H-, 13C- und 6Li-NMR-Spektren und geben damit wichtige Aufschlüsse über die in Lösung vorliegenden Aggregate und Komplexe. Nachbarschaften von 6Li und 1H lassen sich zudem durch Kern-Overhauser-Experimente nachweisen und die 6(7)Li-NMR-Austauschspektroskopie liefert Informationen über Mechanismen und Energetik in Lösung ablaufender dynamischer Prozesse wie Aggregataustausch und Komplexierung. Anwendungsbereiche dieser neu konzipierten ein- und zweidimensionalen NMR-Experimente werden  -  nach einer kurzen Beschreibung der wichtigsten experimentellen Aspekte sowie der typischen NMR-Parameter dieser Verbindungsklasse  -  anhand ausgewählter Beispiele erläutert. Die Ergebnisse zeigen, daß von hochauflösenden NMR-spektroskopischen Untersuchungen lithiumorganischer Verbindungen in Zukunft noch detailliertere Auskünfte über Struktur und Reaktionsweisen dieser für die organische Synthese wichtigen Stoffklasse zu erwarten sind.
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