Figure 13

Chromatography and Mass spectra of peptide HLIFCHSK crosslinking with dGdU. (A) Chromatograph shows that the peptide eluted at 6.92 minutes. (B) MS spectrum of the crosslinked peptide. CLPM calculated that the doubly-charged precursor ion 770.808 (2H+) has a mass value of 1539.6326Da, which closely matches this crosslinked peptide whose expected mass is 1539.620394Da. The mass difference is 7.93 ppm. The triply-charged ion of this crosslinked peptide can also be found at 514.2 (3H+). In the MS/MS spectrum (C), fragmentation led to some b, y-type and internal fragments of the peptide and of the nucleic acids that were assigned to some of the peaks as shown.