PEPTIDE AMINO-ACID-SEQUENCE ANALYSIS USING MATRIX-ASSISTED LASER-DESORPTION IONIZATION AND FOURIER-TRANSFORM MASS-SPECTROMETRY

High-performance matrix-assisted laser desorption/ionization (MALDI) u sing 7 T Fourier transform mass spectrometry (FTMS) was investigated f or peptide amino acid sequence analysis. Two synthetic peptides repres entative of the type which would be displayed by major histocompatibil ity complex molecules from tumor cells were investigated by MALDI/FTMS . Molecular ions of the two 9-amino acid peptides were detected with r esolving power of 8000-17900 and mass measurement accuracy between 8 a nd 81 ppm for the all C-12 isotope ions. An ultra-high resolution spec trum (RP 300 000) for the molecular ion of one of the two peptides was obtained. Structurally useful sequence information was obtained by us e of surface-induced dissociation (SID) of the molecular ion species. Interestingly, SID of a sodium-attached peptide molecular ion resulted in the production of numerous sodium-attached sequence ions.