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  • 1995-1999  (44)
  • 1985-1989  (41)
  • 1925-1929
  • 1880-1889
  • 1850-1859  (1)
  • Chemistry  (77)
  • Genetics  (6)
  • Engineering  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Regulation of NAD metabolism in Salmonella typhimurium: Genetic analysis and cloning of the nadR repressor locus (1987)
    Springer
    Molecular genetics and genomics 208 (1987), S. 279-287 
    Details
    ISSN: 1617-4623
    Keywords: NAD metabolism ; Regulation ; nadR ; Salmonella typhimurium ; Genetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The nadR locus (99 min) controls the transcription of several genes involved with either the biosynthesis (nadAB) or recycling (pncB) of NAD in Salmonella typhimurium. Point mutations in this locus were found to cause defects either in the transport of nicotinamide mononucleotide (PnuA-), the regulation of nadAB (NadR-) or both transport and regulation (PnuA-NadR-). Deletions or insertions into nadR always resulted in the PnuA- NadR- phenotypes. Merodiploids constructed with various combiminations of PnuA-, NadR- or PnuA-NadR- strains indicate a single complementation group. The results suggest the NadR product is a bifunctional regulatory protein. Operon fusions to lacZ (nadR:: Mud1-8) were used to show that nadR is not autoregulated and is transcribed in a clockwise direction. The gene was also cloned and located within a 2 kb EcoR1-BglII fragment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00330454
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  • 2
    Electronic Resource
    Electronic Resource
    The pyridine nucleotide cycle of Salmonella typhimurium: Genetic characterization of the pncXA operon (1986)
    Springer
    Molecular genetics and genomics 205 (1986), S. 507-514 
    Details
    ISSN: 1617-4623
    Keywords: Pyridine nucleotide cycle ; NAD metabolism ; Salmonella typhimurium ; Genetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A series of Mud1 and Tn10 insertions were identified in the pncA chromosome region of Salmonella typhimurium which is responsible for the production of nicotinamide deamidase. Both pncA (resulting in no nicotinamide deamidase activity) and pncX (resulting in lowered nicotinamide deamidase activity) insertions were constructed. In addition, mutants which could utilize nicotinamide as a sole source of nitrogen were isolated. These mutants, designated pncH, hyperproduce nicotinamide deamidase. Genetic studies utilizing pncX-lacZ and pncA-lacZ operon fusions indicate that pncX::Tn10 insertions reduce transcription of pncA-lac while pncH mutations increase the expression of both pncA-lacZ and pncX-lacZ. The gene order was determined as purB-pncA-pncX-gdh with transcription of both pncA and pncX occurring in the counterclockwise direction. Merodiploid studies suggest a model whereby pncX and pncA form an operon with the major promoter occurring upstream from pncX. A second, weaker promoter for pncA must be situated between pncX and pncA. The pncH mutations appear to occur in the pncX promoter (pncXp) increasing promoter activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00338090
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  • 3
    Electronic Resource
    Electronic Resource
    Multiple denaturational transitions in fibrillar collagen (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1875-1893 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The heat denaturation of pepsinized bovine nonfibrillar and fibrillar collagen was studied by differential scanning calorimetry. For fibrillar preparations that had been rapidly precipitated with stirring at low ionic strength, then resuspended at physiological ionic strength, multiple denaturational transitions were observed. At heating rates of 10°C/min, melting endotherms occurred at about 44, 50, 53, and 57°C. Fibrillar collagen that was slowly gelled without stirring at physiological ionic strength exhibited a similar series of endotherms, but the lower melting transitions were less conspicuous. In contrast, nonfibrillar bovine collagen in acidic solution showed only a single denaturational transition at 40°C. Nonfibrillar solutions at pH 7, to which inhibitors of fibrillogenesis were added, showed a major endotherm as high as 46°C. These results suggest that reconstituted fibrillar collagen contains a heterogeneous fibril population, possibly including molecules in a nonfibrillar state. It was proposed that the multiple melting endotherms of such preparations were due to sequential melting of molecular and fibril classes, each with a distinct melting temperature. The fibrillar classes may represent three or more types of banded and nonbanded species that differ from each other in packing order, collagen concentration, and possibly also in fibril width and level of cross-linking.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360251006
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of pH and temperature on cardioactive polypeptides from sea anemones: A 1H-nmr study (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 1143-1157 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effects of pH and temperature on the 300-MHz 1H-nmr spectra of three cardioactive polypeptides from sea anemones, anthopleurin-A from Anthopleura xanthogrammica (AP-A) and Anemonia sulcata toxins I and II (ATX I and II), are described. AP-A and ATX II exhibit major spectral heterogeneity. Evidence from the pH and temperature studies and from high performance liquid chromatography indicates that this heterogeneity is conformational rather than chemical in origin. By contrast, purified isotoxins of ATX I show no evidence of conformational heterogeneity. The pKa values of most of the ionizable groups in these polypeptides are not strongly perturbed by interactions in the tertiary structure, with the exception of one of the Asp carboxylates, which has a pKa of ≲ 2 in AP-A and ATX II and 3.0 in ATX I. Protonation of this carboxylate, suggested to be Asp-9, leads to a conformational change in all three molecules. All three polypeptides are thermally stable, showing some conformational changes but not major unfolding at elevated temperatures.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360270708
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  • 5
    Electronic Resource
    Electronic Resource
    A small-angle x-ray scattering study of alginate solution and its Sol-Gel transition by addition of divalent cations (1995)
    New York : Wiley-Blackwell
    Biopolymers 35 (1995), S. 227-238 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The small-angle x-ray scattering (SAXS) technique has been applied to investigate solution and gel structures of alginate in the absence and presence of two divalent cations: Ca(II) and Cu(II). We have observed a broad maximum in the scattering curve, a characteristic of polyelectrolyte, for the purified alginate sample. The scattering maximum disappears in excess of added simple salt and shifts toward the higher angle region with increasing alginate concentration. Concentration dependence of the position and intensity of the maximum follows power law relations with exponents close to those predicted by theory. Data analysis shows an increase in correlation length ξ and cross-sectional diameter d0, of polymer chains upon gelation and suggests that a dimeric structure is adopted in the junction zone, consistent with the “egg-box” model previously proposed. In the Ca(II)-alginate system, the molecular parameters ξ and d0 are found to have good correlation with the macroscopic properties of gelation, such as gel point determined by viscosity measurements. However, for the Cu(II)-alginate system there is no clearly transitional behavior observed in ξ and d0, implying that the junction zone may be replaced by a more uniformly distributed site binding of Cu(II) ions to the carboxyl groups of both mannuronate and guluronate residues, in confirmation of previous 13C-nmr results. © 1995 John Wiley & Sons, Inc.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360350211
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  • 6
    Electronic Resource
    Electronic Resource
    Crystal Smectic-B Phase from a Mesomorphic Ferrocene Derivative (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1215-1218 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermal properties of two ferrocene derivatives, substituted by either one or two cholesteryloxycarbonyl units, were investigated. While the monosubstituted ferrocene derivative 1 was found to be non-mesomorphic, the disubstituted ferrocene derivative 2 exhibited a crystal smectic-B phase. This result shows that ferrocene-containing thermotropic liquid crystals, despite the bulkiness of the metallocene core, are not limited to disordered calamitic phases.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19950780514
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  • 7
    Electronic Resource
    Electronic Resource
    Synthesis and structure of Cp3U=CHPMe3: A compound with a U=C multiple bond (1988)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 121 (1988), S. 417-420 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthese und Struktur von Cp3U=CHPMe3: Eine Verbindung mit U=C-MehrfachbindungGrünes, kristallines Cp3U=CHPMe3 wurde durch Umsetzung von Cp3UCl mit Li[CH2]2PMe2 oder H2C=PMe3 dargestellt. Seine Kristallstruktur wurde durch Röntgenbeugungsanalyse an Einkristallen bestimmt. Der kurze U=CH-Abstand von 2.274(8) Å und der große Winkel U—C—P von 143.5(5)° deuten Uran-Kohlenstoff-Mehrfachbindungscharakter an. Die 1J (13C1H)-Kopplungskonstanten in den CH-Gruppen zwischen Uran und Phosphor von Cp3U=CHPMe3 (95 Hz), Cp3U=CHPMe2Ph (100 Hz) und Cp3U=CHPPh2Me (113 Hz) sind auffallend klein. Den Strukturdaten kann aber keine agostische UCHP-Wechselwirkung entnommen werden.
    Notes: Green, crystalline Cp3U=CHPMe3 has been synthesized by the reaction of Cp3UCl with Li[CH2]2PMe2 or CH2=PMe3. Its crystal structure has been determined by single crystal X-ray diffraction. The short U=CH bond distance, 2.274(8) Å, and large U—C—P angle, 143.5(5)°, indicate uranium-carbon multiple bond character. The 1J(13C1H) coupling constants within the CH group between uranium and phosphorus in Cp3U=CHPPh2Me (95 Hz), Cp3U=CHPMe2Ph (100 Hz), and Cp3U=CHPPh2Me (113 Hz) are surprisingly small, but no agostic interaction UCHP can be derived from the structural data.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19881210306
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  • 8
    Electronic Resource
    Electronic Resource
    Supermolecules Containing a Tetrahedral Core: A New Class of Liquid-Crystalline Siloxanes (1996)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 521-525 
    Details
    ISSN: 0009-2940
    Keywords: Liquid crystals ; Siloxanes ; Phase behaviors ; Defined topology ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is shown that supermolecules with a tetrahedral symmetry and appropriate side-chains exhibit liquid-crystalline phase behaviour. The use of an optimised hydrosylation reaction allows for the synthesis of materials that have four mesogenic groups attached to a siloxane core, where the conformation and the configuration are unambiguous. The materials show low glass transition temperatures and, depending on the spacer length, complex liquid-crystalline morphologies.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19961290508
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  • 9
    Electronic Resource
    Electronic Resource
    Evaluation of dielectric cure models for an epoxy-amine resin system (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 339-346 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The parallel-plate test fixture on a Rheometrics viscometer was electrically isolated so that the rheological and dielectric properties of a thermoset polymer system could be simultaneously measured. This enabled the relationship between the dielectric properties and the rheological properties to be directly examined. A close relationship was established between the dielectric properties (dipole relaxation time and specific conductivity) and the pre-gelation bulk viscosity. This relationship suggested that models similar in form to those used to describe the change in viscosity might be used to describe the changing dielectric properties. The limitations and advantages of two such models, which attempt to describe the time-temperature behavior of the dielectric properties, were then tested for use with a typical aerospace epoxy resin system.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760290513
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  • 10
    Electronic Resource
    Electronic Resource
    Two-Dimensional thermal analysis of resistance welded thermoplastic composites (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1722-1729 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A transient two-dimensional thermal model for resistance welding of thermoplastic composites is presented. A parametric study is conducted that yields insight into the welding process enabling some critical process and material parameters to be identified. Time to melt is predicted by the model and is successfully compared to experimental observations. Local heating and meltthrough can also be explained by the transient thermal model in agreement with experimental observations. Mode I fracture toughness of unidirectional graphite reinforced poly(etheretherketone) resistance welded double cantilever beam specimens are conducted under various process conditions. Experimental results indicate that under optimum process conditions, the interlaminar fracture toughness of the bulk compression-molded thermoplastic composite material can be achieved using resistance heating as a joining technique.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760292314
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