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  • Articles  (2)
  • 2015-2019  (1)
  • 1985-1989  (1)
  • 1
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: On the Heterogen-Catalytical Oxidation and Ammoxidation of Isobutene. 5. Gas-Phase Oxidation of Methacrolein to Methacrylic Acid on Definite 1:1 Vanadium PhosphatesFor the Oxidation of Methacrolein (MA) to Methacrylic Acid (MAA) definite 1:1 vanadium phosphates were used as test catalysts. (VIVO)2P2O7 (1) is directing the reaction with high selectivity to MAA. On using the VV monophosphates α-(2) and β-VOPO4 (3), a valence-mixed “H-V/P mica” (with α-based structure; 46.5% VIV portion) (4), and also the new phosphate VIVO(HPO4) (5), however, only a modest selectivity is observed. Whereas the diphosphate 1 was found to be unchanged after the catalytical reaction, in the case of the monophosphates solid state reactions occured during the catalysis: 2 was reduced to a H-V/P mica (6) with 29% VIV portion, 4 to the hemi-hydrate VIV O(HPO4) · 0.5 H2O (7); and from 3, as new compounds, 5 (see above) and a VIII/VIV phosphate (8) were formed. On preparing 5 as a pure phase and using it for the catalysis it mostly remained unchanged; only a minor part was reduced to 8. - The catalytical action of 1 is discussed.
    Notes: Bei der Oxydation von Methacrolein (MA) zu Methacrylsäure (MAA) wurden als Versuchskatalysatoren definierte 1:1-Vanadiumphosphate eingesetzt. (VIVO)2P2O7 (1) lenkt die Reaktion mit hoher Selektivität zu MAA. Beim Einsatz der VV-Monophosphate α-(2) und β-VOPO4 (3) sowie eines valenzgemischten „H-V/P-Glimmers“ (mit α-Grundstruktur; 46,5% VIV-Anteil) (4) und des neuen Phosphates VIVO(HPO4) (5) sind dagegen nur geringe Selektivitäten festzustellen. Während das Diphosphat 1 nach der Katalysereaktion unverändert vorlag, traten bei den Monophosphaten während der Katalyse Festkörperreaktionen ein: 2 wurde zu einem H-V/P-Glimmer (6) mit 29% VIV-Anteil und 4 zu dem Halbhydrat VIVO(HPO4) · 0,5 H2O (7) reduziert, und aus 3 resultierten als neue Verbindungen 5 (s. o.) sowie ein noch näher zu charakterisierendes VIII/VIV-Phosphat (8). Präparativ phasenrein dargestelltes und zur Katalyse eingesetztes 5 blieb im wesentlichen unverändert; nur eine geringe Menge wurde zu 8 reduziert. - Die katalytische Wirkung von 1 wird diskutiert.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2016-07-27
    Description: Increasing morbidity and mortality from Clostridium difficile infection (CDI) present an enormous challenge to healthcare systems. Clostridium difficile express type IV pili (T4P), but their function remains unclear. Many chronic and recurrent bacterial infections result from biofilms, surface-associated bacterial communities embedded in an extracellular matrix. CDI may be biofilm mediated; T4P are important for biofilm formation in a number of organisms. We evaluate the role of T4P in C. difficile biofilm formation using RNA sequencing, mutagenesis and complementation of the gene encoding the major pilin pilA1 , and microscopy. RNA sequencing demonstrates that, in comparison to other growth phenotypes, C. difficile growing in a biofilm has a distinct RNA expression profile, with significant differences in T4P gene expression. Microscopy of T4P-expressing and T4P-deficient strains suggests that T4P play an important role in early biofilm formation. A non-piliated pilA1 mutant forms an initial biofilm of significantly reduced mass and thickness in comparison to the wild type. Complementation of the pilA1 mutant strain leads to formation of a biofilm which resembles the wild-type biofilm. These findings suggest that T4P play an important role in early biofilm formation. Novel strategies for confronting biofilm infections are emerging; our data suggest that similar strategies should be investigated in CDI.
    Print ISSN: 0928-8244
    Topics: Biology , Medicine
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