Assignment of the absolute configuration of the amino acids of pyoverdins by GC/MS

Abstract

Bacterial peptides frequently contain both d- and l-amino acids, proteinogenic as well as uncommon ones. Using the example of pyoverdins, iron chelating chromopeptides of the bacterial genus Pseudomonas, the mass spectrometric assignment of enantiomers of the amino acids in the form of their N(O, S)-perfluoroacyl amino acid alkyl esters after GC separation using a Permabond l-Chirasil Val chiral column is discussed. The identification of the amino acids with different fragmentation patterns is demonstrated even in cases of unresolved peaks by mass spectrometry. A simplified assignment of absolute configuration of the amino acids in low or trace concentrations by mass fragmentography is presented. Although mainly the trifluoroacetyl amino acid isopropyl ester (TFA-IP derivatives) are used for the analysis of pyoverdins, also other N(O, S)-perfluoroacyl alkyl esters can be used due to reliability and enhanced identification power of GC/MS. Chirality 11:381–386, 1999. © 1999 Wiley-Liss, Inc.