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  • 1
    Electronic Resource
    Electronic Resource
    Glyphosate tolerance of cultured Corydalis sempervirens cells is acquired by an increased rate of transcription of 5-enolpyruvylshikimate 3-phosphate synthase as well as by a reduced turnover of the enzyme (1992)
    Springer
    Plant molecular biology 20 (1992), S. 1029-1036 
    Details
    ISSN: 1573-5028
    Keywords: glyphosate ; 5-enolpyruvylshikimate 3-phosphate synthase ; in vitro transcription ; overproduction ; enzyme stabilization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cell cultures of Corydalis sempervirens, tolerant to the herbicide glyphosate, have a 30–40-fold increased level of the herbicide's target enzyme 5-enolpyruvylshikimate 3-phosphate (EPSP) synthase, a ten-fold enhanced level of the corresponding mRNA but no amplification of the gene (Holländer-Czytko et al., Plant Mol Biol 11 (1988) 215–220). The increase at the transcriptional level is due to a higher rate of transcription of the gene, which was observed in run-off transcription assays with isolated nuclei. The further amplification at the protein level is the result of stabilization of the enzyme by the herbicide. In the presence of glyphosate the half-life of EPSP synthase was doubled leading to higher levels of both protein and enzyme activity. Overproduction of the enzyme in adapted cultures is stable at the transcriptional level, as cells from adapted cultures grown in the absence of glyphosate for three years still display an about ten-fold higher enzyme activity and transcript level than non-adapted cultures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00028890
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  • 2
    Electronic Resource
    Electronic Resource
    Molecular basis for the overproduction of 5-enolpyruvylshikimate 3-phosphate synthase in a glyphosate-tolerant cell suspension culture of Corydalis sempervirens (1988)
    Springer
    Plant molecular biology 11 (1988), S. 215-220 
    Details
    ISSN: 1573-5028
    Keywords: glyphosate ; herbicide ; 5-enolpyruvylshikimic acid 3-phosphate (EPSP) synthase ; enzyme overproduction ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cell cultures of Corydalis sempervirens adapted to growth in the presence of 5 mM glyphosate [N-(phosphonomethyl)glycine] display a 30- to 40-fold increase in the cellular content of 5-enolpyruvylshikimic acid 3-phosphate (EPSP) synthase, the target enzyme of the herbicide. Translatable mRNA activity as well as transcript levels for EPSP synthase were increased 8-to 12-fold in the adapted (glyphosate-tolerant) as compared to the non-adapted (glyphosate-sensitive) cultures. Northern blot analysis revealed a single 1.8 kb transcript after hybridization with an oligonucleotide probe deduced from the N-terminal amino acid sequence of the enzyme. No significant differences in the relative abundance of EPSP synthase-specific DNA sequences could be detected, however, in Southern and dot blot analyses of restricted DNA isolated from the two cultures. We conclude that the overproduction of EPSP synthase in glyphosate-tolerant C. sempervirens cells is not based on the amplification of the corresponding gene.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00015673
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  • 3
    Electronic Resource
    Electronic Resource
    Abfangreaktionen kurzlebiger Radikale, VIII. Über die radikalische Substitution am Stickstoff: Reaktionen von 1-Aryl-triazenen mit Organozinn-hydriden (1972)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 105 (1972), S. 1540-1552 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Reactions of Short-Life Radicals, VIII. Radical Substitution at the Nitrogen Atom: Reactions of 1-Aryltriazenes with Organotin HydridesStannyl radicals react with 1-aryltriazenes 1-12, attacking N3 and forming stannyl amines. The reaction proceeds by an SH2α mechanism; the arylazo group is displaced (“induced degradation”) and splits off N2. This is the only reaction in cases 1-5. With 6-12, however, an SH2γ displacement predominates. Here, substituents bound to N3 are able to form fairly well stabilized radicals. Stannyl radicals attack N1, displace the substituent from N3 and form trialkylstannyl triazenes 10-12, 15, 20, which are surprisingly stable because of pentacoordination at the tin atom. The free-radical fragments abstract hydrogen from the tin hydride, releasing new stannyl radicals, which propagate the chain reaction. Hydrostannation of the azo group has not been observed. It is shown that stannyl radicals are capable of reversible addition across the azo double bond.
    Notes: Stannylradikale R3Sn⋅ können 1-Aryl-triazene 1-12 and N3 unter Bildung von Stannylaminen angreifen. Dabei wird in einer SH2α-Reaktion die Arylazogruppe verdrängt (“induzierter Zerfall”) und spaltet N2 ab. Dies tritt bei 1-5 ausschließlich ein. Bei 6-12, die an N3 einen als Radikal stabilisierten Substituenten tragen, überwiegt jedoch eine SH2γ-Reaktion. Der Angriff eines Stannylradikals an N1 verdrängt dabei den Substituenten von N3. Es entstehen Trialkylstannyl-triazene 10-12, 15 und 20, durch Pentakoordination am Zinnatom überraschend stabil. H-Abstraktion aus dem Organozinnhydrid stabilisiert die abgespaltenen Molekülfragmente. Die hinterbleibenden Stannylradikale setzen die Reaktionskette fort. Hydrostannierung der Azodoppelbindung wird nicht beobachtet. Es wird gezeigt, daß sich Stannylradikale reversibel an die Azodoppelbindung addieren können.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19721050510
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  • 4
    Electronic Resource
    Electronic Resource
    Abfangreaktionen kurzlebiger Radikale, XI. Über die radikalische Substitution am Stickstoff: Der induzierte Zerfall von 2-Tetrazenen (1973)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 106 (1973), S. 2395-2407 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Reactions of Short-Life Radicals, XI. Free Radical Substitution at the Nitrogen Atom: The Induced Degradation of 2-TetrazenesThe radical degradation of tetraphenyl-2-tetrazene (1a) and 1,4-dicyclohexyl-1,4-diphenyl-2-tetrazene (1b) is found to be accelerated by trialkyltin hydride. Stannyl radicals attack at N-1 or N-4. In a SH2α reaction, N2, the corresponding stannylamine and a radical ·N(R)R′ are formed. The latter is scavenged by R3SnH giving the amine; or it recombines with a stannyl radical at low hydride concentrations. Dicarbizolyldiazene 1c reacts by the same way, but not so the dipiperidinodiazene (1d). Importance of stabilization of ground and transition states on the spontaneous and the induced degradation are discussed. Values of t1/2, k, ΔH±, and ΔS± are given. Stannyl radicals also accelerate the splitting of tetraphenylhydrazine.
    Notes: Der radikalische Zerfall von Tetraphenyl-2-tetrazen (1a) und 1,4-Dicyclohexyl-1,4-diphenyl-2-tetrazen (1b) wird durch Trialkylzinnhydrid beschleunigt. Beim Angriff von Stannyl-Radikalen an N-1 oder N-4 entstehen in einer SH2α-Reaktion N2, Stannylamin und ein Radikal ·N(R)R′, das durch R3SnH zum Amin abgefangen wird oder mit einem Stannyl-Radikal bei niedriger Hydrid-Konzentration rekombiniert. Auch Dicarbazolyldiazen 1c reagiert analog, nicht jedoch Dipiperidinodiazen (1d). Einflüsse der Stabilisierung von Grund- und Übergangszustand auf den Spontan- wie den induzierten Zerfall werden diskutiert, Werte für t1/2, k, ΔH* und ΔS* angegeben. Auch Tetraphenylhydrazin wird durch Stannyl-Radikale beschleunigt gespalten.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19731060737
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