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  • 1
    Electronic Resource
    Electronic Resource
    Glass capillary gas chromatography of amino acid enantiomers (1979)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 2 (1979), S. 411-415 
    Details
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Capillary, glass ; Enantiomer amino acids separated on chirally functionalized polysiloxane phase ; McReynolds constants of chiral phase given ; HCl gas pretreatment, colloidal silicic acid deposition best wall preparation ; Racemisation tested ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Glass capillaries coated with Chirasil-Val, a chirally functionalised polysiloxane, are capable in principle of resolving all protein amino-acid enantiomers in a single run and within a short analysis time, thus allowing for example the quantitative amino acid determination by enantiomer labelling. The elution characteristics of the individual amino acids however are also dependent upon the chemical nature of the capillary wall surface, and a surface pretreatment is found to be necessary if all protein amino acids are to be analysed. Of the various methods of pretreatment tested, etching of borosilicate glass with gaseous HCl followed by deposition of colloidal silicic acid is considered to be the most suitable.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240020708
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  • 2
    Electronic Resource
    Electronic Resource
    Gas chromatographic mass spectrometric computer analysis of volatile components in blood plasma from hemodialysis patients (1975)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 2 (1975), S. 142-147 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Low molecular weight volatile organics extracted from the plasma of patients before and after hemodialysis were analyzed by high resolution capillary gas chomatographic mass spectrometric computer methods. The volatile components were collected on a polyphenyl ether solid adsorbent prior to analysis. Identification of components was achieved by mass spectrometry. Quantitaive changes were observed in both the plasma and dialysate composition with time. The method described provides a new means whereby the 100 or so low molecular weight organic volatiles of plasma can be monitored during the dialysis procedure.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200020308
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  • 3
    Electronic Resource
    Electronic Resource
    C-methylation: An artifact in peptides derivatized for sequencing by mass spectrometry (1975)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 2 (1975), S. 254-260 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The extent of C-methylation, an artifact of the permethylation procedure used to derivatize peptides for mass spectrometric sequencing, was investigated by mass spectrometry. Ten glycine-containing peptides were N-acetylated and then permethylated by the Hakomori method and analyzed by chemical ionization and, in some cases, by electron ionization mass spectrometry. A comparative study was made of the tripeptides Gly Pro Ala and Ala Pro Gly, derivatized by three permethylation procedures. The results show that while C-methylation occurs primarily at glycine, other amino acids (Gln, Glu, Met, Tyr) are also C-methylated, but to a lesser degree. The extent to which C-methylation occurs varies widely and depends on residue position and on the identity of neighboring residues. Such artifacts could lead to serious errors in peptide sequences determined by mass spectrometry, especially when mixtures of peptides are analyzed.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200020503
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  • 4
    Electronic Resource
    Electronic Resource
    Synthesis and mass spectrometry of deuterated methadone and methadone metabolitesDDP = 1,5-dimethyl-3,3-diphenyl-2-pyrrolidone; EDDP = 2-ethylidene-1,5-dimethyl-3,3-diphenyl pyrrolidine; EMDP =2-ethyl-5-methyl-3,3-diphenyl-1-pyrroline. (1979)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 6 (1979), S. 179-186 
    Details
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Deuterated methadone, 2-ethylidene-1,5-dimethyl-3,3-diphenyl pyrrolidine, 2-ethyl-5-methyl-3,3-diphenyl-1-pyrroline, 1,5-dimethyl-3,3-diphenyl-2-pyrrolidone and 4-dimethylamino-2,2-diphenylpentanoic acid have been synthesized for application to metabolic studies of methadone and as potential internal standards for selected ion monitoring methods. Mass fragmentation patterns are described based upon comparisons between labeled and unlabeled derivatives.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200060502
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  • 5
    Electronic Resource
    Electronic Resource
    Hydrogen migrations in mass spectrometry. V - loss of olefin from n-propyl esters following chemical ionizationPresented, in part, at the American Society for Mass Spectrometry, 23rd Annual Conference on Mass Spectrometry and Allied Topics, Houston, Texas, May 1975. For Part IV, see Ref. 12. (1978)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 13 (1978), S. 128-132 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The sources of the migrating hydrogen in the elimination of propylene from the protonated and ethylated n-propyl acetate and n-propyl benzoate molecules have been determined by studying the CH4 and H2 chemical ionization mass spectra of esters specifically deuterated in the propyl group. It is shown that the migrating hydrogen originates from C-1 ( ∼ 27%), C-2 ( ∼ 23%) and C-3 ( ∼ 50%) of the propyl group, independent of ester and mode of ionization. It is argued that the observed reaction involves specific competing H-migration reactions from each propyl position to the ether oxygen in a keto-protonated (ethylated) ester molecule.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210130303
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  • 6
    Electronic Resource
    Electronic Resource
    13C-NMR-Untersuchungen zur Strukturaufklärung von Polysacchariden und deren MethylderivatenDiese Arbeit gilt als 6. Mitteilung der Reihe Strukturuntersuchungen an Polysacchariden; (5. Mitteilung s. Lit. 1). (1979)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 12 (1979), S. 216-222 
    Details
    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 13C NMR spectra of some polysaccharides and their methyl derivatives have been analysed. The numbers and positions of the assigned 13C NMR signals give some information about the structure of the monomer unit and the positions of the glycosidic linkage but no information about the anomeric configuration. In this case the 1J(C-1, H) coupling constants make it possible to identify the anomeric configuration, because the mean differences of the J values for the α- and β-anomers are 12 Hz (at least 5 Hz) with the higher values for the α-anomers.
    Notes: Die 13C-NMR-Spektren einer Reihe von Polysacchariden und ihrer Methylderivate wurden aufgenommen, zugeordnet und für die methylierten Polysaccharide außerdem die Kopplungskonstanten 1J(CH) bestimmt. An Beispielen wird gezeigt, daß die Zahl der 13C-Signale und deren Lage im Spektrum Aussagen über den Aufbau der Polysaccharide, sowie über die Verknüpfungsstellen der glykosidischen Bindung gestatten. Während aus den Signallagen die anomere Konfiguration nicht eindeutig zu ermitteln ist, gelingt dies bei den methylierten Polysacchariden mit Hilfe der Kopplungskonstanten 1J(C-1, H); diese weisen Unterschiede von durchschnittlich 12 Hz (aber mindestens 5 Hz) zwischen den α- und β-Anomeren auf, wobei die gröβeren Werte den α-Anomeren entsprechen.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270120410
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  • 7
    Electronic Resource
    Electronic Resource
    A dynamic nuclear magnetic resonance study of nitrogen inversion in N,N'-dimethylimidazolidine (1979)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 12 (1979), S. 362-364 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 251 MHz 1H and the natural-abundance 63.1 MHz 13C NMR spectra of N,N'-dimethylimidazolidine have been measured from -50 to -170°C. Below about -140°C. nitrogen inversion in the compound becomes slow on the NMR time scale and both the 1H and the 13C spectra indicate that it exists in solution as a mixture of cis and trans conformations having nearly the same energies. The free-energy barrier (ΔG≠) for nitrogen inversion in N,N'-dimethylimidazolidine is 6.4 kcal mol-1, a value which is 1.5 kcal mol-1 lower than that for N-methylpyrrolidine.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270120607
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  • 8
    Electronic Resource
    Electronic Resource
    Hydrogen migrations in mass spectrometry. I - The loss of olefin from phenyl-n-propyl ether following electron impact ionization and chemical ionization (1976)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 11 (1976), S. 599-608 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using specifically labelled compounds we have made a detailed study of the source of the hydrogen transferred in the elimination of C3H6 from the molecular ion of phenyln-propyl ether following electron impact ionization and from the protonated (and ethylated) molecule following chemical ionization. The migrating hydrogen originates from all three positions of the npropyl group but not in the ratio expected for randomization of the alkyl hydrogens prior to transfer. The source of the migrating hydrogen is similar for both electron impact ionization and chemical ionization, indicating that the factors governing the rearrangement are the same for both modes of ionization. From a comparison of the results for labelled 2,6-dimethyl phenyl n-propyl ethers with the results for the unsubstituted ether it is concluded that hydrogen transfer occurs only to the ether oxygen and not to the phenyl ring. A two-step mechanism involving a set of competing reversible hydrogen transfer reactions followed by C—O bond cleavage is proposed to explain the results.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210110606
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  • 9
    Electronic Resource
    Electronic Resource
    13C n.m.r. chemical shifts of carbodiimides (1976)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 8 (1976), S. 327-328 
    Details
    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. chemical shifts of the sp-hybridized carbons in dialkylcarbodiimides have values of δc ≃ 140. These shifts are compared with those of similarly hybridized carbons occuring in other classes of compounds.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270080613
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  • 10
    Electronic Resource
    Electronic Resource
    Carbon-13 nuclear magnetic resonance spectra and conformations of cis,cis-1,5-cyclooctadiene monoepoxide and cis, syn,cis-1,5-cyclooctadiene diepoxide (1979)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 12 (1979), S. 299-301 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The natural-abundance 13C NMR spectra of cis,cis-1,5-cyclooctadiene monoepoxide and cis,syn,cis-1,5-cyclooctadiene diepoxide have been investigated over the temperature range of - 10 to - 180°C. Whereas the spectra of the former showed no dynamic NMR effect, two different conformations in the ratio of 3:1 were observed at low temperatures for the latter. The free-energy barrier (ΔG≠) for conversion of the major conformation to the minor conformation is calculated to be 5.9°0.2 kcal mol-1 from a line-shape analysis of spectra obtained at intermediate temperatures. It is shown that cis,syn,cis-1,5-cyclooctadiene diepoxide exists in solution in chair (major) and in twist-boat (minor) conformations of slightly different energies. Interconversion paths between these conformations are discussed. The monoepoxide is suggested to have a twist-boat conformation that is rapidly pseudorotating via a boat conformation even at - 180°C.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270120510
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