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  • Analytical Chemistry and Spectroscopy  (81)
  • 1990-1994
  • 1970-1974  (81)
  • 1974  (81)
Collection
Publisher
Years
  • 1990-1994
  • 1970-1974  (81)
Year
  • 1
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mass spectra of a series of stable isotope derivatives aided a structure elucidation study of an amino acid amide (Tyr-NH2) and the following family of synthetic oligopeptides: Gly-Tyr-NH2, Gly-Gly-Tyr-NH2, Gln-Gly-Gly-Tyr-NH2, Gln-Gln-Gly-Gly-Tyr-NH2, Ala-Gln-Gln-Gly-Gly-Tyr-NH2, Ser-Ala-Gln-Gln-Gly-Gly-Tyr-NH2 and Lys-Ser-Ala-Gln-Gln-Gly-Gly-Tyr-NH2. This series of peptides was synthesized by classical methods. N,O-permethylated, N-acetylated derivatives were synthesized to provide sufficient volatility for mass spectrometry. Various combinations of stable isotope derivatives (CH3CO + CH3, CD3CO + CH3, CH3CO + CD3, CD3CO + CD3) confirmed proposed fragmentation pathways and corroborated hypothetical ion structures. This family of oligopeptides corresponds to the C-terminus of scotophobin.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 1 (1974), S. 418-422 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An analog multiple ion detection system has been developed for magnetic sector mass spectrometers based on accelerating voltage alternation in conjunction with the accurate maintenance of focusing by means of voltage sweeping, using a superimposed a.c. sine wave voltage. This multiple ion detector voltage sweep system is easily constructed, inexpensive and produces analytical data of much greater precision than that reported from conventional systems. The application of the multiple ion detector voltage sweep system to biomedical problems is illustrated by the development of a method for the determination of stable isotope enrichment in blood glucose and alanine in children infused with tetradeuterio-L-alanine and dideuterioglucose to study gluconeogenesis and glucose utilization in vivo.
    Additional Material: 5 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 1 (1974), S. 5-9 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The field ionization and electron impact mass spectra of eleven coumarins have been compared. In the field ion spectra the molecular ions were the base peaks and structurally diagnostic fragment ions formed by direct cleavage were present, whereas the molecular ions were weak in the electron impact spectra and fragment ions formed by rearrangement were dominant. Crude coumarin mixtures obtained from natural sources have been successfully examined using field ionization and gas chromatography + field ionization mass spectrometry.
    Additional Material: 4 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 6 (1974), S. 503-507 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The carbon-13 NMR spectra of 16 aliphatic phosphorus compounds with -PCl2, -P(OCH3)2, -P(CH3)2 or -PS(CH3)2 groups were determined and interpreted on the basis of the usual α, β-deshielding and γ-shielding effects. The α-effects of all the groups were quite large (15 to 30 ppm), though the β-effects were small (0 to 3 ppm). The γ-effects were also small (0·2 to 1·6 ppm), but of significance in suggesting reduced steric compression relative to that found for methyl and most of the common organic functional groups. This may be attributed to the greater length of the C—P bond. The phosphorus-31 NMR spectra of these compounds also show the existence of interaction with γ-carbons by exhibiting small additive upfield shifts.
    Additional Material: 7 Tab.
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  • 5
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Substituent chemical shifts for the title systems have been determined at infinite dilution in CDCl3 from a study of 40 derivatives. An excellent correlation is found between the ortho effect of substituents in the thiophene ring and the corresponding effects in thiophene itself, indicating negligible perturbation by the fused rings. Long range effects of 2- and 3-substituents on the 5- and 6-protons are electronic in origin, but cannot be interpreted in terms of simple resonance theory. These long range effects correlate linearly with σp°. An O, S-cis conformation for the formyl group in 2-formyl-thieno[2,3-6][1]benzothiophene is adduced on the basis of chemical shifts.
    Additional Material: 5 Tab.
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  • 6
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The NMR spectra of eight spirophosphoranes bearing a P—H bond have been recorded in the presence of europium NMR shift reagent. The spectra are simplified by addition of the europium chelate. The observed displacements in the proton NMR lines allow the assignment of the endo and exo signals in some cases. By addition of the NMR shift reagent, one observes a displacement in the phosphite-spirophosphorane equilibrium in some cases.
    Notes: Le spectre de Résonance Magnétique Nucléaire de huit spirophosphoranes à liaison P—H a été enregistré en présence de chélate d'europium. L'addition du complexe d'europium amène la levée partielle ou totale de dégénérescence des spectres. Les modifications observées dans les déplacements chimiques permettent de proposer une attribution de position endo ou exo de certains signaux. L'addition du complexe d'europium entraîne, dans certains cas, une modification de l'équilibre entre les formes phosphites et spirophosphoranes.
    Additional Material: 1 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 6 (1974), S. 360-361 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Boron-carbon coupling constants were obtained from the 13C FT-NMR, 1H noise decoupled spectra of sodium tetraphenylboron and tetra-n-butylammonium tetraphenylboron. The appearance of the spectra, as well as values obtained for J(BC), are discussed and contrasted with previously published data.
    Additional Material: 1 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 9 (1974), S. 1086-1094 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The field ionisation investigation of some stereoisomeric alkenes and alkyl halides reveals differences in the fragmentation behaviour with respect to direct bond rupture. As observation by itself of the thermodynamic stability of stereoisomeric molecules, or rather of their structure, does not suffice entirely to explain the observed differences, we offer here an interpretation of experimental results based on the interaction of the stereoisomeric compounds with the strong electric field. Finally, some fundamental conclusions are drawn about the applicability of the field ionisation method to the differentiation between stereoisomers.
    Additional Material: 3 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 2 (1974), S. 593-607 
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Raman spectra of neat liquid cis-2-butene and cis-2-butene-benzene mixtures, covering the accessible composition range at 20°C and atomospheric pressure, have been obtained. Parameters of the benzene bands at 605.6, 1178 and 991.6 cm-1 and cis-2-butene bands at 395.5, 871.5 and 1660 cm-1 are reported. Changes in the parameters as a function of concentration are interpreted in terms of a weak dipole-induced dipole interaction and the consequent effect on rotational motions and resonance energy transfer.
    Additional Material: 9 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 1 (1974), S. 281-285 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mass spectra of most nucleosides of cytosine exhibit molecular ions of low abundance, rearranged ions base + 2H in greater abundance than the companion species base + H, and a characteristic and abundant ion which corresponds to base + C2HO from the sugar. Deuterium, oxygen-18 and substituent labeling showed the presence of C-1′, 2′, H-2′ and O-4′ in the latter ion, which led to a proposed mechanism of formation involving opening of the sugar ring and recyclization between O2 and C-2′ with expulsion of water. Primary driving force for the reaction is due to resonance stabilization promoted by unshared electrons from N4, which results in diminished abundance in the case of imino isomers and derivatives which contain electron-withdrawing groups at N4, and enhanced abundance resulting from methylation at N4. Data for 24 nucleosides are presented and discussed in terms of the determination of nucleoside structure.
    Additional Material: 3 Ill.
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