Complementary linker fragment ions (P1+203 and P2-34) and (P1+169 and P2-SH) generated by the thioether bond fragmentation also have a metastable component for their origin (see filled and empty circles and stars, Figures ). However, their formation seems to be not so favored like the cases P1+71 and P2+98 in (P1-P2)H (Figures and) and probably other mechanisms involving beta elimination and proton transfer mediated their formation (Fig. and Fig. ). 18 showing the incorporation of 18 O in the linker-containing fragment ions (Fig. ).