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  • 1
    Electronic Resource
    Electronic Resource
    Serine 90 Is Required for Enzymic Activity by tRNA-Guanine Transglycosylase from Escherichia coli (1994)
    s.l. : American Chemical Society
    Biochemistry 33 (1994), S. 7041-7046 
    Details
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/bi00189a004
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Identification of the most intense volatile flavour compounds formed during autoxidation of linoleic acid (1987)
    Springer
    European food research and technology 184 (1987), S. 277-282 
    Details
    ISSN: 1438-2385
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Description / Table of Contents: Summary The volatile compounds formed during autoxidation of linoleic acid and methyl linoleate at 22–24 °C were analysed by high resolution gas chromatography and eluate sniffing. The application of this technique to stepwise diluted extracts of the volatile compounds allowed the determination of a new parameter, theD-value, which reveals the most intense flavour compounds of an extract. Hexanal, 2(Z)-octenal and 2(E)-nonenal exhibited the highestD-values in both lipids. 1-Octen-3-ol followed in the case of linoleic acid and 1-octen-3-one in that of methyl linoleate. The grading of the flavour compounds was dependent on the autoxidation time. 2(E)-Nonenal was the most potent aroma compound up to 24 h of linoleic acid autoxidation. After 48 h aldehyde and hexanal and after 72 h hexanal and 2(Z)-octenal possessed the highestD-values. TheD-value can also be used for the approximation of odour threshold values as demonstrated for 2(Z)-octenal, 2(E)-nonenal and 1-octen-3-ol.
    Notes: Zusammenfassung Die flüchtigen Verbindungen, die bei der Autoxidation von Linolsäure und Methyllinoleat bei 22–24 °C entstehen, wurden durch Capillar-Gaschromatographie und sensorische Beurteilung des Trägergasstromes analysiert. Die Anwendung des Verfahrens auf schrittweise verdünnte Extrakte ermöglichte die Bestimmung eines neuen Parameters, desD-Wertes, der die intensivsten Aromastoffe einer Probe anzeigt. Hexanal, 2(Z)-Octenal und 2(E)-Nonenal ergaben in beiden Lipiden die höchstenD-Werte. Bei Linolsäure folgte 1-Octen-3-ol und bei Methyllinoleat 1-Octen-3-on. Die Rangfolge der Aromastoffe war von der Autoxidationszeit abhängig. Nach 24stündiger Autoxidation von Linolsäure erschien 2(E)-Nonenal als stärkster Aromastoff. Nach 48 h ergaben dieser Aldehyd und Hexanal und nach 72 h Hexanal und 2(Z)-Octenal die höchstenD-Werte. Wie für 2(Z)-Octenal, 2(E)-Nonenal und 1-Octen-3-ol gezeigt, ist derD-Wert auch zur näherungsweisen Bestimmung von Geruchsschwellen geeignet.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01027663
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Export and activity of hybrid FhuA′-′Iut receptor proteins and of truncated FhuA′ proteins of the outer membrane of Escherichia coli (1989)
    Springer
    Molecular genetics and genomics 216 (1989), S. 230-238 
    Details
    ISSN: 1617-4623
    Keywords: E. coli ; FhuA receptor ; Membrane insertion ; C-terminus ; Activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The FhuA protein in the outer membrane of Escherichia coli serves as a multifunctional receptor for the phages T5, T1, ϕ80, for colicin M, for ferrichrome (Fe3+-siderophore) and for the structurally related antibiotic, albomycin. To determine structural domains required for these receptor functions and for export, a fusion protein between FhuA and Iut (receptor for Fe3+-aerobactin and cloacin DF13) was constructed. In the FhuA′-′Iut hybrid protein, 24 amino acids of FhuA were replaced by 19 amino acids, 18 of which were from Iut. The number of plaque forming units of phage T5 and T1 on cells expressing FhuA′-′Iut was nearly as high as on cells expressing plasmid-encoded wild-type FhuA. However, 107-fold higher concentrations of phage ϕ80 and 103 times more colicin M were required to obtain a zone of growth inhibition. Truncated FhuA′ proteins in which the last 24 amino acids at the carboxy-terminus were replaced by 16 (FhuA′2) or 3 (FhuA′T) amino acids could hardly be detected on polyacrylamide electrophoretograms of outer membrane proteins, due to proteolytic degradation. Sensitivity of cells expressing FhuA′2 to phage T5 and T1 was reduced by several orders of magnitude and sensitivity to phage ϕ80 and colicin M was totally abolished. In contrast, cells expressing FhuA′T were nearly as sensitive to phage T5, T1, and ϕ80 and to colicin M as cells containing FhuA′-′Iut. None of the constructs could grow on ferrichrome as sole iron source and none was sensitive to albomycin. Ferrichrome did not inhibit binding of T5 to TonB− cells expressing FhuA′-′Iut (as it did in FhuA+ cells) due to the lack of ferrichrome binding. It is concluded that very small deletions (relative to the size of FhuA with 714 amino acids) at the C-terminal end render FhuA susceptible to proteolytic cleavage. The C-terminal alterations affect sensitivity to FhuA-specific agents very differently. Apparently, the C-terminus is a very important part of FhuA regarding stability and activity. Expression of active FhuA and partially inactive FhuA derivatives in the same cell revealed no negative complementation, suggesting a FhuA monomer as functional unit.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00334361
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    Paper (German National Licenses)
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