Figure 3

HCD-MS2 of immunopurified SA2-Aβ1-15 from CSF samples. (A) Full range MS2 spectrum of SA2-Aβ1-15 glycopeptide immunopurified from pooled CSF (Route 1, Fig. 2B) demonstrating glycosidic and peptide backbone fragmentation and (B) expansion of the m/z 100–220 region showing typical oxonium ions. Oxonium ions originating from the HexNAc are marked a and oxonium ions originating from the Neu5Ac are marked b. The relative intensities of the HexNAc ions and the calculated “GlcNAc/GalNAc” ratio are boxed. His is from the histidine side chain immonium ion.