Peptide sequencing of charged derivatives by postsource decay MALDI mass spectrometry

Derivatization procedures for peptides are described that can be performed with sub-picomolar amounts of sample and that are able to direct the formation of fragment ions in Postsource Decay (PSD) MALDI mass spectrometry. Location of a fixed charge (a quarternary ammonium ion) at the N-terminus of a peptide and modification of internal arginine residues (deletion of strong basicity) leads to a full controllability of fragment ion formation resulting in mostly complete series of N-terminal fragment ions. The method appears to be favorably applicable to sequence analysis of unknown peptides, since in most cases the amino acid sequence can directly be read from the spectrum. (C) 1997 Elsevier Science B.V.