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  • Agrobacterium tumefaciens  (1)
  • Hydroxy-functionalized dendrons  (1)
  • 1
    ISSN: 1617-4623
    Keywords: Agrobacterium tumefaciens ; fixNOQP operon ; respiration ; cytochromec oxidase ; Rhizobiaceae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Hybridization analysis using theRhizobium meliloti nitrogen fixation genefixN as a probe revealed the presence of a homologous DNA region in the phytopathogenic bacteriumAgrobacterium tumefaciens. Hybridization signals were also detected with total DNAs ofRhizobium leguminosarum bv.phaseoli, Rhodobacter capsulatus andEscherichia coli, but not those ofXanthomonas campestris pv.campestris andPseudomonas putida. The hybridizing fragment fromA. tumefaciens was cloned and sequenced. The predicted gene product of one of the two open reading frames identified on the sequenced fragment shows homology to FixN of differentRhizobiaceae as well as a low but significant similarity to subunit I of heme copper oxidases from various bacteria. The presence of five strictly conserved histidine residues previously implicated in forming ligands to heme and CuB in oxidases and the predicted membrane topology provide evidence that theA. tumefaciens fixN-like gene product is a component of the heme copper oxidase superfamily. The incomplete open reading frame starting only 8 nucleotides downstream of thefixN-like gene exhibits homology toRhizobium fixO. Using anuidA (GUS) gene fusion it could be shown that theA. tumefaciens fixN-like gene is preferentially expressed under microaerobic conditions. Expression of theuidA fusion is abolished inR. meliloti fixJ andfixK mutants, indicating that an Fnr-like protein is involved in transcriptional regulation of thefixN-like gene in A.tumefaciens. The presence of an upstream DNA sequence motif identical to the Fnr-consensus binding site (anaerobox) further supports this hypothesis.A. tumefaciens mutated in thefixN-like gene shows decreased TMPD-specific oxidase activity under microaerobic conditions, indicating that thefixN-like gene or operon codes for proteins involved in respiration under reduced oxygen availability.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2551-2556 
    ISSN: 1434-193X
    Keywords: Dendrimers ; Hydroxy-functionalized dendrons ; Orthogonal protective groups ; Building blocks ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A convenient and practical multi-gram procedure for the synthesis of second- (G2; 4a, 5a, 5d) and third-generation (G3; 6a) dendrons with orthogonally protected functional groups in the periphery (hydroxy) and at the focal point (carboxylic acid) is described. It uses the amply available first-generation dendrons with amine and carboxylic ester functions (1) and tetrahydropyranyl-protected hydroxy and carboxylic acid functions (2b, 3), respectively, which are connected via amides by peptide methods. Purification is either done by recrystallization or simple filtration through silica gel and yields the products as analytically pure materials on a several-gram scale (even for G3). ‘The dendrons’ protective groups are proven to be orthogonal (500-MHz NMR) which makes them useful components (building blocks) of a future dendron construction kit for a versatile synthesis of, for example, dendronized polymers.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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