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  • 1995-1999  (2)
  • 1985-1989  (2)
  • Crystal structure  (2)
  • Cyanobacteria  (2)
  • 1
    ISSN: 1432-072X
    Keywords: Cyanobacteria ; DNA restriction and cloning ; Gene fusions ; Leucine biosynthesis ; Mutant complementation ; Nostoc ; Transcription
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Genomic DNA extracted from the symbiotically-competent, heterocyst-forming cyanobacterium Nostoc sp. strain 7801 was resistant to cleavage by a number of restriction endonucleases. A cosmid library of Nostoc DNA was prepared and maintained in the modification-limited Escherichia coli strain HB101. Analysis of cloned Nostoc DNA fragments indicated infrequent occurrence of restriction endonuclease recognition sites in the Nostoc genome. The Nostoc genomic library was screened for sequences complementing mutations in the E. coli leucine and proline biosynthetic operons. Two cosmids complementing leuB were isolated but none for leuA, leuC, leuD, or proA were detected in 1000 cosmids. A 3.0 kb fragment subcloned from one of the cosmids complemented mutations in leuB when inserted into the HindIII site of pBR322 in either orientation, demonstrating that transcription of leuB originated within the cloned fragment. The cloned fragment also carries a second site capable of initiating transcription of fused antibiotic resistance genes. While transcription of Nostoc DNA sequences did occur in E. coli, unknown barriers must also exist that prevented additional biological complementation of specific E. coli mutations.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1617-4623
    Keywords: Cyanobacteria ; Nitrate reductase mutants ; Nitrite reductase mutants ; Regulatory mutants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Eighteen mutant strains of the unicellular cyanobacterium Anacystis nidulans R2 that are unable to assimilate nitrate have been isolated after transposon Tn901 mutagenesis. Characterization of phenotypes and transformation tests have allowed the distinction of five different mutant types. The mutants exhibiting a nitrate reductase-less phenotype were identified as being affected in previously defined loci, as they could be transformed to the wild type by one of the plasmids pNR12, pNR63 or pNR193, which contain cloned genes of A. nidulans R2 involved in nitrate reduction. The mutations in strains FM2 and FM16 appear to affect two other genes involved in nitrate assimilation. Strain FM2 apparently bears a single mutation which results in both lack of nitrite reductase activity and loss of ammonium-promoted repression of nitrate reductase synthesis. FM16 has a low but significant level of nitrate reductase that is also freed from repression by ammonium, and an increased level of nitrite reductase activity. FM16 exhibited properties which indicate that this mutant strain might also be affected in the transport of nitrate into the cell.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 547-549 
    ISSN: 1434-1948
    Keywords: Copper ; Trinuclear ; Formamidines ; Magnetism ; Crystal structure ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In situ reaction of CuII triflate with aminopyridine or aminopyrimidine and triethylorthoformate in ethanol results in unique linear trinuclear CuII complexes with the general formula [Cu3(L-)4](CF3SO3)2(EtOH)x (L = dehydronated ligand N,N′-bis(pyridine-2-yl)formamidine or the new ligand N,N′-bis(pyrimidine-2-yl)formamidine). The structure [Cu-Cu-Cu angle 175.19(2)°] consists of four nearly flat molecules of the ligand which contribute to the propeller-type structure around the Cu-Cu-Cu axis. A strong antiferromagnetic interaction between the CuII ions is observed, resulting in an S = 1/2 ground state below 100 K.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1434-1948
    Keywords: Copper ; Methoxo-bridged complexes ; Crystal structure ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A novel chelating ligand, synthesized in situ within the coordination sphere of CuII from 2-amino-3-methylpyridine, MeOH, and dioxygen from the air, is found to form a strongly coupled, dinuclear methoxo-bridged CuII compound with the formula [Cu(L)(CH3O)(NO3)]2 (L = 2-methoxymethylamino-3-methylpyridine). The geometry around the copper atom is square pyramidal and the Cu-Cu distance within the dinuclear unit is 3.011(2) Å with an Cu-O-Cu angle of 103.13(8)°. Synthesis, X-ray crystal structure, and magnetism are reported.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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