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  • Chemistry  (63)
  • Polymer and Materials Science  (28)
  • Physics  (6)
  • 1975-1979  (37)
  • 1970-1974  (32)
  • 1965-1969
  • 1975  (37)
  • 1974  (32)
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  • 1975-1979  (37)
  • 1970-1974  (32)
  • 1965-1969
Year
  • 1
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 1109-1114 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 6 Ill.
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  • 2
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Darstellung von Poly(γ-p-biphenylmethyl-L-Glutamat), PBPLG, (Poly{L-imino-1-[2-(4-biphenylmethoxycarbonyl)äthyl]-2-oxoäthylen}), (1d) wird beschrieben. Das Viskositätsverhalten dieses Polymers in Mischungen aus Benzol und Dichloressigsäure (c=0,2.10 - 3 - 1,4.10 - 3g/cm3) bei 25°CC wird untersucht. Die Ergebnisse werden verglichen mit Messungen unter den gleichen Bedingungen an Poly(γ-benzyl-L-Glutamat),PBLG, (Poly[ L-imino-l-(2-benzyloxycarbonylathyl)-2-oxoathylen]), (lc). In beiden Fallenfindet ein zweistufiger Ubergang von einer starren, von Wasserstoffbrucken stabilisiertenHelix in ein statistisches, solvatisiertes Knduel statt : PBPLG (erste Stufe CrSSX,, zweite Stufe 55-100%, Dichloressigsaure und PBLG (erste Stufe 0-70%, zweite Stufe 70-100%,Dichloressigsaure)).Die Einfiihrung eines p-Phenylsubstituenten in PBLG fuhrt deshalb in Mischungen aus Benzol- und Dichloressigsaure zu einer weniger stabilisierten Helix.Die Stabilitat und das Viskositatsverhalten von PBLG in Mischungen aus Benzol und Dichloressigsaure (c=0,2.10-3 -14.10-3g/cm3) sind denjenigen von PBLG in Mi-schungen aus m-Kresol und Dichloressigslure ( c = 1,0.10-3-4,0. 10-3g/cm3) ähnlich.
    Notes: The synthesis of poly(γ-p-biphenylmethyl-L-glutamate), PBPLG, (poly{L-imino-1-[2-(4-biphenylylmethoxycarbonyl)ethyl]-2-oxoethylene}), (1d) is described. The viscosity behavior of this polymer in benzene/dichloroacetic acid mixtures (c=0,2.10 - 3 - 1,4.10 - 3 g/cm3) at 25°CC is investigated. The results are compared with measurements on poly(γ-benzyl-L-glutamate), PBLG, (poly[L-imino-1-(2-benzyloxycarbonylethyl)-2-oxoethylene]), (1c) under the same conditions. A transition from a rigid hydrogen bonded helix to a random solvated coil occurs in two stages for both: PBPLG (first stage 0 - 55%, second stage 55 - 100% dichloroacetic acid) and PBLG (first stage 0 - 70%, second stage 70 - 100% dichloroacetic acid).Therefore, the introduction of a p-phenyl substituent in PBLG leads to a less stable helix in benzene/dichloroacetic acid mixtures.The stability and viscosity behavior of PBLG in benzene/dichloroacetic acid mixtures (c=0,2.10 - 3 - 1,4.10 - 3g/cm3) is quite similar to the behavior of PBLG in m-cresol/dichloroacetic acid mixtures (c=1,0.10 - 3 - 4,0.10 - 3 g/cm3).
    Additional Material: 4 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 2 (1975), S. 82-89 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Identification of hydrazine monoamine oxidase inhibitor drugs such as isoniazid, iproniazid, nialamide, isocarboxazid and iproclozide is made by electron impact mass spectrometry using the direct insertion technique. The molecular ion itself, although of low relative abundance, is found in the mass spectra of all compounds studied. Relative intensities of the major fragments and data on metastable ions useful in the identification of these compounds are reported. With the aid of synthesized structurally related products, deuterium labelling of exchangeable hydrazidic and hydrazinic protons and by the use of hexadeuterated isopropylic analogues, detailed information about fragmentation patterns is obtained. Splitting processes are chiefly governed by the nature of the aromatic substituent at the hydrazidic end and the alkyl sidechain located at the second hydrazinic nitrogen. The major fragmentations occurring are loss of small neutral molecules, double rearrangement, cleavage of the N—N bond, amide bond rupture, β-cleavage to the hydrazinic nitrogen atom and McLafferty rearrangements.
    Additional Material: 1 Tab.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 57 (1974), S. 2276-2288 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermal rearrangement of [18]annulene in solution gives benzene and 1,2-benzo-1,3,7-cyclooctatriene. This reaction has been investigated using a differential scanning calorimeter and the associated enthalpy change has been measured. The enthalpy of the reaction (in the gase phase at 298°K) is \documentclass{article}\pagestyle{empty}\begin{document}$$ \Delta {\rm H}_{\rm r} \left({{\rm g},\,298^ \circ } \right) = - 50.7 \pm 5\,{\rm kcal mol}^{{\rm - 1}} $$\end{document} From this value and the enthalpies of formation of the reaction products, the enthalpy of formation of [18]annulene is obtained: \documentclass{article}\pagestyle{empty}\begin{document}$$ \Delta {\rm H}_{\rm f} \,^ \circ \left({{\rm 1,}\,{\rm g},\,298^ \circ } \right) = 124 \pm 5.5\,{\rm kcal mol}^{{\rm - 1}} $$\end{document} The stabilization energy of [18]annulene, defined as the difference between the enthalpy of formation of the hypothetical Kékulé [18]annulene (with single and double bonds of normal lengths) and the heat of formation of the real molecule is then \documentclass{article}\pagestyle{empty}\begin{document}$$ \Delta {\rm H}_{{\rm stab}{\rm .}} \left({\rm 1} \right) = 37 \pm 6\,{\rm kcal mol}^{{\rm - 1}} $$\end{document} a value close to the corresponding quantity found for benzene.The very large stabilization energy of [18]annulen (100 ± 6 kcal mol-1) previously reported in the literature, based on measurements of the heat of combustion, is not correct since the annulene is certainly oxidized in the bomb prior to combustion.The isodynamic conformational mobility of [18]annulene is not incompatible with a stabilization energy of 37 kcal mol-1; the activation enthalpy observed for this process (ΔH≠ = 16.1 kcal mol-1) indicates that the stabilization is not completely destroyed in the transition state.The mechanism of the thermolysis of [18]annulen, investigated by kinetic measurements and by analysis of the shape of the thermograms, is discussed.
    Additional Material: 4 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 6 (1974), S. 601-602 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Carbon-13 NMR chemical shifts have been measured in a number of binary mixtures of normal alkanes. Intrinsic solvent shifts are deduced from the shifts and the relevance of some small substituent effects in alkanes is discussed. A comparison is made between solvent effects and thermally induced chemical shift differences in alkanes.
    Additional Material: 3 Tab.
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  • 6
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 7 (1975), S. 415-417 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 13C NMR spectra of the most important hop bitter substances are analysed. All individual carbon atoms are assigned, except the oxygen bonded sp2 carbon atoms. Most assignments are made partly by comparison with analogous compounds and partly by reference to literature data. Cross-correlations with the 1H NMR shifts are made for two main products and confirm the correctness of the assignments. All data are in agreement with the known structures.
    Additional Material: 2 Tab.
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  • 7
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 2211-2230 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis and characterization of a series of sequential polypeptides with the repeating sequences Aze-Pro-Aze, Pro-Aze-Pro, Pro-Aze-Gly, Aze-Pro-Gly, Ala-Aze-Gly, Aze-Ala-Gly, and Pro-Pro-Gly are reported. The polymers were prepared by the active ester method, using the p-nitrophenyl, pentachlorophenyl, and N-hydroxysuccinimide esters as the polymerizable tripeptide derivatives. Except for poly(Ala-Aze-Gly) obtained via the N-hydroxysuccinimide ester, all polymers were isolated in good yields and have weight-average molecular weights in the range 10,000-30,000. The molecular weights have been determined by applying the calibrated gel chromatography system described by Fairweather et al. [J. Chromatogr. (1972) 67, 157] and by viscometry. All di- and tripeptide intermediates were chemically and optically pure.
    Additional Material: 3 Ill.
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  • 8
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using the free energy difference between double-helix and random-coil forms of DNA as a measure of the stability of the double helix, we calculate the dependence of the stability on excess univalent cation concentration and on polynucleotide phosphate concentration, both as functions of the equivalent ratio r of divalent cation-to-phosphate concentrations. The theoretical tool is merely to compare the free energy of one polyelectrolyte solution, characterized by the polyelectrolyte linear charge density, with the free energy of another, characterized by a different value of the charge density. It is assumed only that the charge density of the double helix is greater than that of the coil form. The calculation represents the only molecular theory given to date (for r ≠ O) for these aspects of helix stability.We find that, as excess univalent cation concentration increases, the helix stability increases if r is small but decreases if r is large (i.e., of the order of unity). Moreover, as the concentration of nucleotide phosphate increases, the helix stability does not change for small values of r but increases for large values. For both effects, a continuous transition as a function of r bridges the low-r and high-r behaviour.
    Additional Material: 2 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 1667-1684 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conformational analysis of double-stranded helical polynucleotides was carried out in terms of internal and external parameters, using semiempirical energy potential functions. The results obtained show that the structures proposed on the basis of the X-ray analysis for A-DNA and RNA's are almost identical to those corresponding to the conformational energy minima, whereas that proposed for B-DNA still appears to suffer from conformational strains. On the other hand, the B-DNA structure theoretically predicted is stabilized by both van der Waals energy and possible specific interactions with water molecules and counterions. This may explain the stability of the B form with respect to the A form at high relative humidity and ion strength. A possible role of the A + T fraction in stabilizing the B-type DNA emerges in connection with its preferential ability to bind ions. This agrees with the results on the crystalline structures of GpC and ApU. For RNA's, the occurrence of only A-type structures is explained as being due to the C(3′)-endo puckering of ribose in a double helix.
    Additional Material: 13 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 2441-2443 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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