Fig. 3.
MSn analysis of a representative DSBSO interlinked peptide (α-β) from in vivo cross-linked human 293 cells. A, top: graphic illustration of characteristic fragmentation of a DSBSO interlinked peptide (α-β) during collision-induced dissociation (CID) in MS2. Bottom: MS1 and MS2 spectra of the representative cross-linked peptide (m/z 869.15524+). In the MS2 spectrum, two pairs of peptide fragments (i.e. αA/βT (m/z 590.312+/1139.502+) and αT/βA (681.312+/1048.002+)) were detected. αA, βA, and KA are alkene modified species (+54 Da); αT and βT are unsaturated thiol modified species (+236 Da). B, respective MS3 spectra of αA (m/z 590.312+) and βA (1048.002+) fragments detected in MS2. The detection of a series of y and b ions unambiguously identified their sequences as FANYIDKAVR and QKAQASHAQLGDAYDQEIR, respectively. C, integration of MSn data identified this peptide as a DSBSO interlinked peptide (i.e. [FANYIDK120VR] cross-linked to [QK139QASHAQLGDAYDQEIR]).