CAD MS/MS spectrum of triply acetylated H2A.Z peptide 1–19. The ion selected for dissociation was the [M + 2H]2+ ion (m/z 1041.1). The amino acid sequence is shown above the spectrum, and the masses above and below the sequence correspond to the theoretical b- and y-type product ions, respectively. The masses provided are the monoisotopic, nominal masses of the product ions. The observed, singly protonated b- and y-type ions are underlined and are assigned to their corresponding m/z peaks in the spectrum. The observed, doubly protonated ions are denoted with asterisks. The acetylated lysines (K4, K7, and K11) are indicated with ac. The unacetylated amino groups were derivatized with propionic anhydride and are denoted with pr.