Analysis of multiply charged monomer and dimer ions of the amyloid β(1-28) peptide using electrospray ionization mass spectrometry and collision-induced dissociation.

Tandem mass spectrometry (MS) fragmentation patterns of the Aβ1-28 monomer indicated that the entire 1-28 sequence dissociated during collision-induced dissociation (CID) process of the M2+, M3+, and M4+ ions. Meanwhile, MS/MS analysis of the dimer showed that D5+ dissociates into M2+ and M3+ monomer units and that peptide bond fragmentations occurred in the 1 to 7 and 17 to 28 residue regions of the M3+ subunit. These results suggest that dimerization involves interactions in the 8 to 16 residue region of the M3+ subunit rather than the 1 to 7 or 17 to 28 residue region.