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  • Best von Kryptanden, Kryptaten  (1)
  • DNA-Directed RNA Polymerases/*chemistry/genetics/*metabolism  (1)
  • 1995-1999  (1)
  • 1975-1979  (1)
  • 1
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    Mapping of catalytic residues in the RNA polymerase active center (1996)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1996-07-05
    Description: When the Mg2+ ion in the catalytic center of Escherichia coli RNA polymerase (RNAP) is replaced with Fe2+, hydroxyl radicals are generated. In the promoter complex, such radicals cleave template DNA near the transcription start site, whereas the beta' subunit is cleaved at a conserved motif NADFDGD (Asn-Ala-Asp-Phe-Asp-Gly-Asp). Substitution of the three aspartate residues with alanine creates a dominant lethal mutation. The mutant RNAP is catalytically inactive but can bind promoters and form an open complex. The mutant fails to support Fe2+-induced cleavage of DNA or protein. Thus, the NAD-FDGD motif is involved in chelation of the active center Mg2+.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Zaychikov, E -- Martin, E -- Denissova, L -- Kozlov, M -- Markovtsov, V -- Kashlev, M -- Heumann, H -- Nikiforov, V -- Goldfarb, A -- Mustaev, A -- New York, N.Y. -- Science. 1996 Jul 5;273(5271):107-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Limnological Institute, Russian Academy of Sciences, Irkutsk, Russia.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8658176" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Aspartic Acid/metabolism ; Binding Sites ; DNA/metabolism ; DNA-Directed RNA Polymerases/*chemistry/genetics/*metabolism ; Dithiothreitol/pharmacology ; Electrophoresis, Polyacrylamide Gel ; Escherichia coli/*enzymology ; Ferrous Compounds/metabolism ; Hydroxyl Radical ; Magnesium/metabolism ; Molecular Sequence Data ; Mutagenesis ; Promoter Regions, Genetic
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 2
    Electronic Resource
    Electronic Resource
    Titrimetric determinations of cryptands and cryptates (1979)
    Springer
    Fresenius' Zeitschrift für analytische Chemie 298 (1979), S. 358-362 
    Details
    ISSN: 1618-2650
    Keywords: Best von Kryptanden, Kryptaten ; Volumetrie ; HCl, Metall-Standardlösung, Standardzugabeverfahren
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Summary Using bromocresol green as a visual endpoint indicator solutions of the cryptands [2.2.1] and [2.2.2] can be determined by titration with HCl in the concentration range of 10−1–10−3 M with relative standard deviations of 0.2–0.4 %. If both cryptand and cryptate are present in one solution, then the sum of them can be determined titrimetrically in the same way. It is also possible to determine the contents of [2.2.1] and [2.2.2] by using a calcium or barium standard solution and the unknown cryptand solution as a titrant. By evaluation of the pH-curve thus obtained, the endpoint of the titration can be determined. In the concentration range of 10−1–10−2 M relative standard deviations of about 0.5% are obtained. [2.2.1] cryptand solutions are determined by using the standard addition technique of Gran with a calcium chloride solution. An ion-selective electrode is used as a probe for calcium ions. If this method is applied, the relative standard deviation in the range of 10−2–10−4 M solutions is approximately 3%. With this technique cryptand can be analysed even when cryptate is present in the solution.
    Notes: Zusammenfassung Bei Verwendung von Bromkresolgrün als visueller Endpunktindicator kann man [2.2.1] und [2.2.2] Kryptandlösungen im Konzentrationsbereich 10−1–10−3 M mit relativen Standardabweichungen von 0,2–0,4% mit HCl titrieren. Wenn in einer Lösung sowohl Kryptand als auch Kryptat vorhanden ist, ist die Summe beider Substanzen auf die gleiche Weise bestimmbar. [2.2.1] und [2.2.2] können auch dadurch bestimmt werden, daß eine Calciumbzw. Barium-Standardlösung mit der Kryptandlösung unbekannter Konzentration titriert wird. Die Auswertung der dabei erhaltenen pH-Kurve ergibt den Titrationsendpunkt, wobei hierdurch im Konzentrationsbereich von 10−1–10−2 M Kryptandlösungen relative Standardabweichungen von etwa 0,5% erreicht werden. [2.2.1] Kryptandlösungen werden außerdem mit der Standard-Additionstechnik nach Gran bestimmt, wobei eine calciumselektive Elektrode als Indicatorelektrode dient. Dabei werden im Konzentrationsbereich von 10−2–10−4 M relative Standardabweichungen von etwa 3 % erhalten. Diese Methode kann auch überschüssigen Kryptand neben Kryptat bestimmen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00482014
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