FAB MASS-SPECTRA OF PEPTIDES .9. FORMATION OF N H3PO4 AND N H3PO4 + 62 ADDUCTS ON H3PO4-SPIKED GLYCEROL MATRICES

We have studied the behavior of the brain pentapeptide leucine-enkephalin on phosphoric acid spiked glycerol matrices under FAB-PI conditions. Ion series of the general formula [mM+nH3PO4+H]+, [mM+H+62]+ and [mM+H3PO4+H+62]+ were observed. Experiments using labelled glycerol, methionine-enkephalin and various spiking agents were performed along with B/E linked scans in order to investigate the nature of the latter two series of ions; they led to the conclusion that the +62 ions originate from the slow decomposition of H3PO4-peptide aggregates.