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  • Chemistry  (213)
  • Cell & Developmental Biology  (15)
  • 1975-1979  (228)
  • 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
    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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  • 3
    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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  • 4
    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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  • 5
    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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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 8 (1979), S. 159-163 
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Brown algae, which are good indicators for estuarine metal pollution, can advantageously be analysed by energy-dispersive X-ray fluorescence. The use of thin film samples and samples of intermediate thickness has several advantages over the conventional thick pellet procedure. A quite homogeneous thin target is prepared by suspending 15 mg of dried and ground seaweed powder in bi-distilled water and evaporating the slurry on a 10 cm2 Mylar foil held in a Teflon ring. The effective sample weight in the beam is calculated by a procedure based on the scatter peaks in the spectrum. Sensitivities are typically in the 2-15 ppm range. The coefficient of variation per analysis averaged over ten elements amounts to 10%. The natural concentration variation in seaweed specimens at one location is 13%. Samples from locations in the more polluted western Scheldt estuary yield significantly higher values for several elements, relative to the eastern Scheldt sites. Possible trace element variations between the top and base of plants, and between different seaweed specimens and sampling seasons, are discussed.
    Additional Material: 1 Ill.
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  • 7
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Carbon-13 NMR spectra of the σ-adduct complexes formed in liquid ammonia between the amide ion and some 2-R-pyrimidines, some 4-chloro-2-R-pyrimidines (R = dimethylamino-, N-methylanilino, piperidino-, morpholino-, phenyl-), 5-bromo-2-piperidinopyrimidine and pyrimidine itself are described, together with the carbon-13 NMR spectra of the anions formed by amino-proton abstraction resulting from the reaction of the amide ion with 2-anilino-4-chloro-, 4-chloro-2-methylamino-, 2-anilino- and 2-methylaminopyrimidine in liquid ammonia. Additionally, the carbon-13 NMR spectra of the parent compounds of the anionic σ-adducts and anions, and that of 4-chloropyrimidine, were recorded in CDCl3.
    Additional Material: 1 Tab.
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  • 8
    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.
    Additional Material: 4 Tab.
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  • 9
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 10 (1977), S. 165-168 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 13C n.m.r. spectra of the N-methylated mono- and diazanaphthalenes have been recorded and analysed. It has been shown that N-methylation as well as N-protonation in cinnoline occur predominantly at the β-nitrogen atom. N-methylation and N-protonation show a similar effect on the 13C chemical shifts.
    Additional Material: 1 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 11 (1978), S. 316-318 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The γ-effects of sulphur on 13C NMR chemical shifts have been measured in a series of steroidal compounds containing the thiophene ring in different configurations with respect to the rest of the molecule. The data constitute the first example of downfield effects exerted by sulphur on both gauche and antiperiplanar γ-carbons. The γ-gauche effect of sulphur amounts to 1.6-1.8 ppm, the γ-antiperiplanar effect from practically zero to almost 1 ppm.
    Additional Material: 1 Tab.
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