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  • 1
    Electronic Resource
    Electronic Resource
    The determination of low d5-phenylalanine enrichment (0.002-0.09 atom percent excess), after conversion to phenylethylamine, in relation to protein turnover studies by gass chromatography/electron ionization mass spectrometry (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 421-424 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A gas chromatography/mass spectrometry (GC/MS) method for measuring very low levels of enrichment of d5-phenylalanine (0.002-0.09 atom percent excess) is described. This method makes it possible to determine the enrichment of amino acid incorporated into tissue protein during studies of protein synthesis in man. Phenylalamine is enzymatically converted to phenylethylamine and the d5-enrichment is measured in the heptafluorobutyryl derivative by selective-ion recording under electron ionization conditions. The coefficients of variation for muscle-protein hydrolysate samples enriched with d5-phenylalanine at the 0.005 and 0.05 atom percent excess levels were 6.0 and 1.2%, respectively. This precision at low enrichment and the small amount of contrast to the conventional approach which uses GC/MS for plasma amino acids (typically 2-20 atom percent excess) but gas isotope-ratio mass spectrometry for protein-bound amino acids, the enrichment of both plasmafree and protein-bound d5-phenylalanine can be measured with a single instrument.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290060704
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Baseline measurements for stable isotope studies: An alternative to biopsy (1990)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 19 (1990), S. 176-178 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Studies of protein metabolism with stable isotopes require determination of the ‘natural’ isotopic enrichment in tissues. This has previously been determined by taking a pre-test muscle biopsy or by using the isotopic enrichment of a separate control group of subjects. In this study we have measured and compared the “natural” 13C enrichment of leucine in plasma protein and muscle protein in 14 subjects. The mean enrichment of leucine (δ13CPDB) in muscle protein, -26.627, was not significantly different from that in plasma protein, -27.152. The data indicate that the 13C enrichment of leucine in plasma protein reflects that of muscle protein and provides an attractive alternative to an additional muscle biopsy in studies of protein metabolism with stable isotopes.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200190314
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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