Figure 13.

ETD MS/MS product ion spectra of the triply protonated peptide
VVDLMVH*MASK from GAPDH in vitro-modified by HNE (([M+3H]3+, m/z 462.59). Complete cn- and zn-type fragment ion series are observed. ETD did not induce retro-Michael addition of HNE. Asterisks denote the fragment ions that retained the HNE modification. The ETD-MS/MS experiment was performed with an Orbitrap XL equipped with an ETD module. Fluoranthene radical anions were generated in the CI ion source and then transferred into the linear trap (unpublished data).