FAST-ATOM-BOMBARDMENT TANDEM MASS-SPECTROMETRY OF BENZYLOXYCARBONYL-PROTECTED TETRAPEPTIDE DERIVATIVES CONTAINING PROLINE

Fragmentations of N-benzyloxycarbonyl-protected tetrapeptide ethyl est ers containing L-proline and L-alanine in the gas phase were examined by the collisional-activated decomposition of the deprotonated molecul e and the fragment ions produced by the cleavage of the tetrapeptide d erivatives, in which changes in both the number and positions of the p rolyl residues were observed, in negative-ion FAB-MS, The cleavage pat terns of these ions in the collisional-activated decomposition mass sp ectra were observed to depend on the number and positions of prolyl re sidues in the peptide derivatives, These results indicate that the con formational difference in the tetrapeptide derivatives due to the exis tence of L-proline may be an important factor responsible for the frag mentations of peptide molecules in the gas phase.