Formation of Aβ oligomeric assemblies and fibrils
Consistent with previous results13,14,20, the ESI mass spectrum of Aβ1-40 shows primarily multiply charged ions of the monomer, ranging from +2 to +6 (Fig. 2b). Furthermore, weak signals corresponding to multiply charged ions of the dimer (+5 to +7) were also observed in the ESI mass spectrum. These ions were more pronounced in the analysis of Aβ1-40 by ESI-IMS-MS, where signals corresponding to Aβ1-40 oligomers ranging from dimer to heptamers were readily detected in the ESI-IMS-MS driftscope plot of the Aβ1-40 monomer (Fig. 2c), thus demonstrating formation of Aβ1-40 aggregated species. This is apparently due to the formation of Aβ1-40 oligomers (dimers to heptamers) early in the process of fibril assembly. Co-populated oligomeric ions with the same m/z were separated and identified individually by ESI-IMS-MS (e.g.,…
