Technique for Measuring Picomolar Amounts of Bound and Unbound Amino Acids Obtained from Myogenic Cell Cultures of Skeletal Muscle

A procedure is described that compares the isotope dilution method of measuring picomolar amounts of amino acids obtained from cellular extracts with a direct method of analysis. Evidence is provided that shows that the direct method is at least as accurate as the isotope dilution method. In addition the direct method is as expedient and requires but a single isotope and fewer chromatograms for analysis. A procedure also is described for selecting the appropriate conditions for dansylation and for measuring the loss of dansyl amino acid due to decomposition.