Fig. 3.
MSn analysis of DSSO heterodimeric interlinked peptide of cytochrome c (α-β: Ac-GDVEKGKK interlinked to KKGER). A, MS/MS spectrum of [α-β]4+ (m/z 419.97164+) in which two fragment pairs were observed: αA (m/z 478.992+)/βT (m/z 352.402+) and αT (m/z 494.962+)/βA (m/z 336.422+). B, MS3 spectrum of αA (m/z 478.992+) in which detection of y1–y7 and b2–b7 determined the sequence unambiguously as Ac-GDVEKAGKK. C, MS3 spectrum of βT (m/z 352.402+) in which detection of y1–y4, a1, and b2–b7 ions determined the sequence unambiguously as KTKGER. KA is modified with the alkene moiety, and KT is modified with the unsaturated thiol moiety.