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  • 2020-2022  (47)
  • 1985-1989  (40)
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  • 1
    Electronic Resource
    Electronic Resource
    DABCO-catalyzed coupling of aldehydes with activated double bonds. 4. Stereoselective synthesis of trisubstituted olefins and terpenoid building blocks via 2-(hydroxyalkyl)-2-propenoic esters (1985)
    s.l. : American Chemical Society
    The @journal of organic chemistry 50 (1985), S. 3849-3859 
    Details
    ISSN: 1520-6904
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/jo00220a034
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  • 2
    Electronic Resource
    Electronic Resource
    Vibunazole and Its Enantiomers (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 544 (1988), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1988.tb40390.x
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  • 3
    Electronic Resource
    Electronic Resource
    Gluconate accumulation and enzyme activities with extremely nitrogen-limited surface cultures of Aspergillus niger (1986)
    Springer
    Archives of microbiology 144 (1986), S. 151-157 
    Details
    ISSN: 1432-072X
    Keywords: Aspergillus niger ; Nitrogen limitation ; Gluconate accumulation ; Enzyme activities
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Batch cultures of Aspergillus niger grown from conidia on a medium with high C/N ratio accumulated gluconate from glucose with a yield of 57%. During almost the whole time of accumulation there was no net synthesis of total protein in the mycelium but the activity per flask and the specific activity of glucose oxidase (EC 1.1.3.4) in mycelial extracts increased whereas both values decreased for glucose dehydrogenase (EC 1.1.99.10) ‘gluconate 6-phosphatase’ (cf. EC 3.1.3.1, 3.1.3.2), gluconokinase (EC 2.7.1.12), glucose 6-phosphate and phosphogluconate dehydrogenases (EC 1.1.1.49, EC 1.1.1.44), phosphoglucomutase (EC 2.7.5.1), and most enzymes of the Embden-Meyerhof pathway and the tricarboxylic acid cycle. Gluconate dehydratase (EC 4.2.1.39), gluconate dehydrogenase (EC 1.1.99.3) and enzymes of the Entner-Doudoroff pathway could not be detected. By cycloheximide the increase of glucose oxidase activity was inhibited. It is concluded that the high yield of gluconate was due mainly to the net (de novo) synthesis of glucose oxidase which occurred during protein turnover after the exhaustion of the nitrogen source, and which was not accompanied by a net synthesis of the other enzymes investigated. Some gluconate may also have been formed by hydrolytic cleavage of gluconate 6-phosphate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00414726
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  • 4
    Electronic Resource
    Electronic Resource
    Inhibition of Bradyrhizobium japonicum nifA-dependent nif gene activation by oxygen occurs at the NifA protein level and is irreversible (1989)
    Springer
    Archives of microbiology 151 (1989), S. 191-197 
    Details
    ISSN: 1432-072X
    Keywords: Bradyrhizobium japonicum ; NifA activity ; nifA mRNA half-lives ; Oxygen shift ; Post-transcriptional control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Previous work had shown that Bradyrhizobium japonicum nifA-dependent nif gene activation was inhibited by oxygen via a post-transcriptional mechanism. In the present report we demonstrate that this inhibition occurs at the NifA protein level and that it is irreversible. To narrow down the level of control the influence of oxygen on nifA mRNA stability and NifA protein activity was analyzed. The half-lives of B. japonicum and Klebsiella pneumoniae (control) nifA mRNAs derived from constitutively expressed nifA genes did not differ significantly under aerobic and anaerobic conditions which makes it unlikely that oxygen exerts its effect by selectively destabilizing B. japonicum nifA mRNA. By making use of its ability to activate in Escherichia coli a B. japonicum nifD' — 'lacZ fusion, the NifA protein was assayed by the determination of lacZ mRNA and β-galactosidase synthesis. Oxygen shift experiments clearly demonstrated that B. japonicum NifA activity (but not that of K. pneumoniae) was drastically reduced within minutes upon a shift to aerobiosis and that the inactivation was irreversible.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00413129
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  • 5
    Electronic Resource
    Electronic Resource
    Field desorption and fast atom bombardment mass spectrometry of pyridine nucleotides and nucleoside triphosphates (1985)
    Springer
    Fresenius' Zeitschrift für analytische Chemie 321 (1985), S. 531-537 
    Details
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Summary The complete mass spectra of nicotinamide mononucleotide (free acid), β-nicotinamide adenine dinucleotide (free acid and lithium salt), dihydronicotinamide adenine dinucleotide (disodium salt), nicotinamide adenine dinucleotide phosphate (disodium salt) and adenosine-5′- triphosphate (disodium salt) are introduced. The first comparison of field desorption and fast atom bombardment mass spectrometry of these biologically active phosphates is reported. A critical evaluation of the merits and pitfalls of both soft ionization methods for the investigations of pyridine nucleotides and nucleoside triphosphates is given. In particular, the experimental difficulties for ionic desorption of organic phosphates in FD-MS and the basic problems of chemical noise as well as matrix/substance-interaction in FAB-MS are discussed.
    Notes: Zusammenfassung Erstmals werden die kompletten Massenspektren von Nicotinamid-Mononucleotid (freie Säure), β-Nicotinamid-Adenin-Dinucleotid (freie Säure und Lithiumsalz), Dihydronicotinamid-Adenine-Dinucleotid (Dinatriumsalz), Nicotinamid-Adenin-Dinucleotidphosphat (Dinatriumsalz) und Adenosin-5′-triphosphat (Dinatriumsalz) vorgestellt. Über einen ersten Vergleich der Felddesorptions- und Fast Atom Bombardment-Massenspektrometrie von diesen biologisch aktiven Phosphaten wird berichtet. Eine kritische Wertung der Vor- und Nachteile der beiden schonenden Ionisierungsverfahren für die Untersuchungen von Pyridin-Nucleotiden und Nucleosid-Triphosphaten wird gegeben. Insbesondere werden die experimentellen Schwierigkeiten der ionischen Desorption von organischen Phosphaten bei der FD-MS und die grundsätzlichen Probleme des chemischen Untergrundes sowie der Matrix/Substanz-Wechselwirkung bei FAB-MS angesprochen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00464359
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  • 6
    Electronic Resource
    Electronic Resource
    Identification of nifE-, nifN- and nifS-like genes in Bradyrhizobium japonicum (1987)
    Springer
    Molecular genetics and genomics 207 (1987), S. 503-508 
    Details
    ISSN: 1617-4623
    Keywords: Bradyrhizobium ; Nif genes ; Nitrogen fixation ; Root nodule symbiosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The 17 kb region between the Bradyrhizobium japonicum nitrogenase genes (nifDK and nifH) was investigated for the presence of further nif or fix genes by site-directed insertion or deletion/replacement mutagenesis and interspecies hybridization. Mutant strains were tested for their ability to reduce acetylene in free-living, microaerobic culture (Nif phenotype) and in soybean root nodules (Fix phenotype). The presence of a gene, previously identified by hybridization with the Klebsiella pneumoniae nifB gene, was proved by isolation of a nifB insertion mutant which was completely Nif- and Fix-. Three other regions were found to be homologous to the K. pneumoniae genes nifE, nifN, and nifS, NifE and nifN insertion mutants were completely Nif-/Fix- whereas nifS mutants were leaky with 30% residual Fix activity. Taken together, the data show that the B. japonicum genome harbours a cluster of closely adjacent genes which are directly concerned with nitrogenase function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00331622
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  • 7
    Electronic Resource
    Electronic Resource
    Mapping of Rhizobium japonicum nifB-,fixBC-, and fixA-like genes and identification of the fixA promoter (1985)
    Springer
    Molecular genetics and genomics 199 (1985), S. 315-322 
    Details
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary New DNA regions likely to be involved in symbiotic nitrogen fixation were identified and mapped, by interspecies hybridization, on cloned DNA from the slowgrowing Rhizobium japonicum strain 110. NifB-and fixBC-like genes were located near the nifH and nifDK operons encoding the nitrogenase polypeptides, whereas a fixA-like gene is not linked to this cluster. NifB was detected by interspecies hybridization with a Klebsiella pneumoniae nifA/nifB probe, and its identity was confirmed due to its homology with the Rhizobium leguminosarum nifB gene. NifB of R. japonicum was located between nifDK and nifH at a distance of 11 kb downstream from the 3′ end of nifK. Using the Rhizobium meliloti fixABC operon as heterologous probe it was found that, in R. japonicum, fixA is distantly separated from fixBC. FixB and fixC are probably contained together in one operon (fixBC). The approximate start of fixB was located 2.8 kb downstream of the 3′ end of nifH. All genes of the nifDK-nifB-nifH-fixBC cluster are transcribed in the same direction. The DNA region harboring fixA was identified in a cosmid clone bank. The promoter and transcription start site of fixA were sequenced and mapped by a nuclease S1 protection experiment. The promoter sequence (5′-ATGGTAC-5bp-TTGCT-3′) is very similar to the nif-type consensus promoter sequence. Hence, the expression of R. japonicum nif and fix genes may be regulated coordinately.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00330274
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  • 8
    Electronic Resource
    Electronic Resource
    Direct response of Bradyrhizobium japonicum nifA-mediated nif gene regulation to cellular oxygen status (1987)
    Springer
    Molecular genetics and genomics 209 (1987), S. 621-626 
    Details
    ISSN: 1617-4623
    Keywords: Bradyrhizobium japonicum ; nifA gene ; Nitrogen fixation ; Oxygen control ; Transcriptional control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The nifA genes of Klebsiella pneumoniae and Bradyrhizobium japonicum were constitutively expressed from the pBR329-derived chloramphenicol resistance promoter. The inserts of these nifA plasmid constructs were devoid of any other intact flanking genes. The nifA genes thus expressed led to a marked activation of a B. japonicum nifD-lacZ fusion under microaerobic conditions. Under aerobic growth conditions, however, activation was mediated only by the K. pneumoniae nifA gene but not by the B. japonicum nifA gene. This selective effect was observed in both the Escherichia coli as well as the B. japonicum backgrounds. Several lines of evidence suggest that in these experiments oxygen adversely affects B. japonicum nifA-dependent nif gene regulation at the post-transcriptional level, probably even at the post-translational level, and that this effect does not require a nifL-like gene. Models are proposed in which oxygen inhibits the B. japonicum NifA protein either directly or indirectly via other cellular components involved in general protein oxidation pathways.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00331174
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  • 9
    Electronic Resource
    Electronic Resource
    On the Macrolactonization of β-Hydroxy Acids. Crystal structures of the pentolide and the hexolide from (R)-3-hydroxybutanoic acid. Molecular modeling studies of the tetrolideDedicated to Prof. Dr. Wilhelm Simon on the occasion of his 60th birthday (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 1704-1717 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The temperature and concentration dependence of the previously reported formation of oligolides from (R)- or (S)-3-hydroxybutanoic acid under Yamaguchi's macrolactonization conditions (2,4,6-trichlorobenzoyl chloride/base) was studied. While the content of hexolide 2 in the product mixture is almost invariably ca. 35%, the amounts of pentolide 1 and of the larger rings strongly depend upon the temperature employed (Fig.1). Cyclic oligomers (5,6) are also obtained from 3-hydroxypentanoic acid. Enantiomerically pure β-butyrolactone can be used for the preparation of pento-, hexo-, and heptolide under Shanzer's macrolactonization conditions (tetra-oxadistannacyclodecane ‘template’). The X-ray crystal structures of the pentolide 1 and of two modifications (space groups C 2 and P 21) of the hexolide 2 were determined (Figs. 2-6 and Tables 1 and 5). No close contacts between substituent atoms and atoms in the rings or between ring atoms are observed in these structures. The hexolide C 2 modification is ‘just a large ring’, while the crystals of the P 21 modification contain folded rings the backbones of which resemble the seam of a tennis ball. A comparison of the torsion angles in the folded hexolide ring of the P 21 modification with those in the helical poly-(R)-3-hydroxybutanoate (PHB) suggests (Table 2) that the same interactions might be responsible for folding in the first and helix formation in the second case. Molecular modeling with force-field energy minimization of the tetrolide from four homochiral β-hydroxybutanoic acid units was undertaken, in order to find possible reasons for the fact that we failed to detect the tetrolide in the reaction mixtures. The calculated conformational energies (per monomer) for some of the tetrolide models (Figs. 7-9 and Tables 3 and 4) are not significantly higher than for the pentolide and hexolide crystal structures. We conclude that thermodynamic instability is an unlikely reason for the lack of tetrolide isolation. This result and failure to observe equilibration of pentolide 1 to a mixture of oligomers under the reaction conditions suggest that product distribution is governed by kinetic control.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720807
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  • 10
    Electronic Resource
    Electronic Resource
    Ringöffnung von N-(Tetraalkylamidinio)pyridinium-Salzen durch Anionen methylenaktiver Verbindungen (1986)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 119 (1986), S. 3276-3296 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Ring Opening of N-(Tetraalkylamidinio)pyridinium Salts by Anions of CH-Acidic Methylene CompoundsN-Carbeniopyridinium salts 2, 4, 14, and 18 offer three sites to nucleophilic attack; depending on the reactants, all three modes have been realized. With anions of CH-acidic methylene compounds, α-attack at the pyridinium ring followed by ring opening leads to azahexamethine merocyanines (8, 15, 23). In some cases, kinetically controlled reactions yield 1,4-dihydropyridines which isomerize thermally to give 1,2-dihydropyridines which undergo ring opening spontaneously. Also, nucleophilic attack at the cationic substituent of the N-carbeniopyridinium salts is possible as is indicated by the formation of push-pull olefins 11, 16 and of enol ether 12.
    Notes: Die N-Carbeniopyridinium-Salze 2, 4, 14 und 18 bieten für den Angriff eines Nucleophils drei Möglichkeiten, die sich in Abhängigkeit von den Reaktionspartnern alle realisieren lassen. Mit Anionen methylenaktiver Verbindungen führt der α-Angriff am Pyridinium-Ring unter Ringöffnung zu Azahexamethinneutrocyaninen (8, 15, 23). In einigen Fällen bilden sich kinetisch kontrolliert 1,4-Dihydropyridine, die sich thermisch zu den 1,2-Dihydro-pyridinen bzw. deren ringgeöffneten Folgeprodukten umlagern. Schließlich ist auch der nucleophile Angriff am kationischen Substituenten der N-Carbeniopyridinium-Salze möglich, wie die Bildung der Push-pull-Olefine 11, 16 und des Enolethers 12 zeigt.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19861191109
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