THE DETERMINATION OF LOW D(5)-PHENYLALANINE ENRICHMENT (0.002-0.09 ATOM PERCENT EXCESS), AFTER CONVERSION TO PHENYLETHYLAMINE, IN RELATION TO PROTEIN-TURNOVER STUDIES BY GAS-CHROMATOGRAPHY ELECTRON IONIZATION MASS-SPECTROMETRY

AG CALDER*, Susan Elizabeth Anderson, I GRANT, MA MCNURLAN, PJ GARLICK

*Corresponding author for this work

Research output: Contribution to journalArticle

Abstract

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. Phenylalanine 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 protein needed (about 1 mg) provide real advantages for clinical studies of tissue protein synthesis. Moreover, in 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 plasma-free and protein-bound d5-phenylalanine can be measured with a single instrument.

Original languageEnglish
Pages (from-to)421-424
Number of pages4
JournalRapid Communications in Mass Spectrometry
Volume6
Issue number7
Publication statusPublished - Jul 1992

Keywords

  • MUSCLE

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