The linker fragment ions generated by the dissociation of the other pseudopeptide bond between the amino terminal group of P1 and the thiazine linker were detected at m/z 815.31 and m/z 998.34 and they were assigned to P1 and P2+151 (see empty and filled rhombuses in Figure and), respectively. These linker fragment ions P1 and P2+151), have intensities lower than the ones (P1+71 and P2+80) generated by the fragmentation of the other pseudopeptide bond in the thiazine linker, and newly generated after the transcyclization reaction . P1+71 is approximately 2.3 times more intense than P1, while P2+80 and P2+151 have similar intensities (Figure ).