Isotope derivative analysis for proline, valine, methionine, and phenylalanine.

The development of the isotope derivative method of amino acid analysis and its application to the determination of aspartic and glutamic acids, serine, threonine, and hydroxyproline in protein hydrolysates has been described (1). In order to extend the method and to make possible the identification of the amino end-groups of proteins we have modified the procedure to include glycine and alanine. We have also developed fractionation procedures which permit the quantitative determination of proline, methionine, phenylalanine, and valine by the isotope derivative method in protein hydrolysates.