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  • Chemistry  (213)
  • Physics  (26)
  • Cell & Developmental Biology  (15)
  • 1975-1979  (254)
  • 1
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 9 (1977), S. 281-284 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 13C chemical shifts of the diazanaphthalenes have been recorded as a function of the pH value, providing classical titration curves. From these curves the pK1 and pK2 values have been determined taking into account the activity coefficients. The changes in 13C chemical shift under the influence of nitrogen protonation (Δδ) can be described by two protonation parameter sets.
    Additional Material: 4 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 443 (1978), S. 269-278 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Komplexe von TrialkylphosphinoxidenEs wird über neue Komplexe von Trimethyl-, Tris(hydroxymethyl)-, Triethyl-, Tripropyl-, Tri-isopropyl-, Tributyl-phosphinoxid berichtet. Aussagen über die Strukturen der Komplexe werden mit Hilfe der Schwingungs- und Ligandenfeld-Spektroskopie erzielt. Die verschiedenen Faktoren, welche die Strukturen beeinflussen, werden diskutiert.
    Notes: A number of new complexes containing trimethylphosphine oxide, tris(hydroxymethyl)phosphine oxide, triethylphosphine oxide, tripropylphosphine oxide, triisopropylphosphine oxide and tributylphosphine oxide is reported. The structures of the complexes have been deduced with the aid of physical measurement such as vibrational and ligand-field spectroscopy. The various factors that influence the structure of phosphoryl solvates and adducts are discussed.
    Additional Material: 2 Tab.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 60 (1977), S. 367-379 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of isoalloxazine and alloxazine derivatives have been investigated by 13C-NMR. The synthesis of selectively 13C-enriched derivatives made it possible to assign unambiguously the signals due to the quaternary carbon atoms at position 4, 4a and 10a of the isoalloxazine ring system. The assignment of the other resonances was ensured by the use of selectively deuteriated and chemically modified compounds as well as by decoupling techniques. The assignments differ in part from those published by Breitmaier & Voelter [2] on FMN and FAD. The solvent dependence of the resonances has been studied in dioxan/water mixtures. The experimental data are compared with published MO calculations and discussed.
    Additional Material: 3 Ill.
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  • 4
    ISSN: 0009-286X
    Keywords: laser-Doppler anemometry ; stirred tank ; agitated vessel ; turbulence power spectra ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 1 Ill.
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  • 5
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Electron impact induced fragmentation of 4-(ω-phenoxymethyl and -ethyl)tetrahydn pyranes results in abundant [M — 93] + ions through loss of a phenoxy radical. These ions are all produced in high yields by isobutane chemical ionization through loss of phenol from the quai molecular ions. Labelling data (2H, 13C) provide evidence for the l-oxoniabicyclo[2.2.1]heptane ai l-oxoniabicyclo[2.2.2]octane structures of the electron impact produced decomposing (ion sour and first field free region) ions [M — 93]L in the case of the methyl and ethyl compounds, respective.
    Additional Material: 1 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 14 (1979), S. 191-195 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Evidence is presented for the formation of cyclic onium ions from bifunctional alkyl phenyl ethers under chemical ionization conditions.
    Additional Material: 4 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 225-235 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The relation between the chemical structure of a protein and the physical properties of a heat-set gel of that protein has been investigated. The physical properties of the gel are determined by means of mechanical experiments in which the viscoelastic properties of the gel are determined in terms of the storage shear modulus, the loss modulus and the stress-strain curve. The storage shear modulus defined the solid (elastic) character of the gel. The chemical structure of the protein and the nature of the solvent determine the nature and number of cross-links in the gel. The cross-links in gels formed by heating concentrated solutions of ovalbumin in 6M urea solutions were found to be disulfide bridges and the mechanical properties of these ovalbumin/urea gels approximated those of an ideal rubber. The latter finding enables one to calculate the number of cross-links per ovalbumin molecule from the value of the storage modulus, using the classical theory of rubber elasticity. This theory, together with the Flory-Huggins lattice model, can also be used to calculate the number of cros-links per ovalbumin molecule from the swelling behavior of ovalbumin/urea gels. The number of cross-links per ovalbumin molecule calculated from these two types of experiments are in mutual agreement and correspond with the number of thiol groups in ovalbumin. We conclude, thereforee, that theories of polymer physics can be used to relate the chemical structure of a protein to the physical properties of its gel.
    Additional Material: 6 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 110 (1977), S. 2758-2764 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Gold Complexes of Diphosphinomethanes, III. AuII Compounds by Means of Oxidative Addition of HalogenOxidative addition of halogen to the 1:2 complexes of bis(diphenylphosphino)methane and -propane with AuCl (1a, 5) leads to products which are formulated partly as AuI/AuIII compounds (2a, b), but partly also as true AuII derivatives (6a, b). The addition of iodine to the AuI complex yields an adduct of the type 4. For the characterisation of the largely insoluble materials, infrared, Mössbauer, and ESCA spectroscopy have been employed.
    Notes: Durch oxidative Addition von Halogen an 1:2-Komplexe von Bis(diphenylphosphino)methan und -propan mit AuCl (1a, 5) entstehen Produkte, die teilweise als AuI/AuIII-Verbindungen (2a, b), teilweise aber auch als echte AuII-Derivate zu formulieren sind (6a, b). Die Anlagerung von Iod an den AuI-Komplex liefert nur ein Addukt vom Typ 4. Zur Charakterisierung der fast ausnahmslos unlöslichen Substanzen wurden die Infrarot-, Mössbauer-und ESCA-Spektroskopie herangezogen.
    Additional Material: 1 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 773-781 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The dielectric relaxation behavior of three sodium polyphosphates with different but low degrees of polymerization in aqueous solution (without salt) has been investigated between 8 kHz and 100 MHz. The highest molecular weight sample (DP 338) exhibits two dispersion regions as is generally observed with synthetic polyelectrolytes at higher degrees of polymerization and is interpreted, according to the theory of van der Touw and Mandel, by attributing a certain flexibility to the polymer chain. The experimentally determined relaxation time of the high-frequency dispersion is in fair agreement with the theoretically calculated value. For the lowest molecular weight sample (DP 112) the experimental results can best be described by a single dispersion curve pointing to a rigid, more or less stretched, conformation of the polyion in agreement with theoretical predictions. For the sample of intermediate molecular weight (DP 198) the situation is borderline as it is possible to describe the relaxation behavior by either one or two dispersion regions; it is, however, concluded from an analysis of the dielectric results that the average conformation is rather extended, but not completely rigid.
    Additional Material: 1 Ill.
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  • 10
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 13C n.m.r. chemical shifts of a number of 1,1-disubstituted ethylenes are presented. Moreover, effects of changing temperatures on the 13C n.m.r. chemical shifts of some of these compounds as well as of three normal alkanes are given. These variations in chemical shifts are attributed to varying amounts of sterically induced shifts in the different conformational equilibria. In addition to the well-known 1,4 interaction between two alkyl groups shielding effects on the carbon atoms of the connecting bonds are also proposed. No definite explanation of this effect is presented at this time. It is further shown that no simple correlations exist between 13C n.m.r. chemical shifts and calculated total charge densities at this level. Instead, the experimental results in 1-alkenes are rationalized by assuming a linear dependence of the 13C n.m.r. chemical shifts of C-1 and C-2 via rehybridizations on changes in bond angles for small skeletal deformations caused by steric interactions. These changes in geometries, as well as conformational energies in three 1-alkenes, were calculated by means of VFF calculations. Finally. upfield shifts for both C-2 and C-4 are proposed for those conformations of 1-alkenes in which the C-3—C-4 group interacts with the pz-orbital of C-2.
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