Mass Spectrometric Amino Acid Sequencing of Short and Mid-Sized Peptides in a ESI-o-TOF System as an Alternative to MS/MS. II: Selective Fragmentation of Dansylated Peptides with Predominant Formation of b-Ions

Abstract

A scheme for analyzing the mass spectra of fragmented peptides, including chemical modification of the N-terminal amino group of the peptide by 5-(N,N-dimethylamino)naphthalene-1-sulfonyl chloride followed by ionization of the dansylated peptide by electrospray and its fragmentation at the low vacuum zone of the sample solution input unit into the mass spectrometer (ESI-o-TOF scheme), has been proposed. It is shown that the resulting ions are fragmented with the predominant formation of b-ions bearing a Dns-group. In this way, it is possible to obtain high-intensity b-ions (peak/noise intensity ratio of 10/1 to 100/1), including b₁ and b₂ ions that are especially valuable for determining the structure. In combination with the previously proposed method of obtaining informative y-ions, this approach allows one to reliably determine the complete amino acid sequence of peptides containing up to 10 amino acid residues, without using computer programs for analyzing the fragment composition of peptides.