[M+ Na]+ top mass peaks and various interesting features. The spectrum of Boc-Ala-azaGln- Gly-OH 12b is used as an example. The major fragmentation pattern corresponds to that observed for simple Boc-amino acids by Garner. 20 (Figure, left-hand pathway). Thus, the M- 56 (loss of C4H8) and M-100 (subsequent loss of CO2) peaks provide the major fragmentation. Another mode of fragmentation, which occurs at 10—15% intensity ...