Figure 4

Transmission electron microscopy images of freshly formed Aβ42 fibrils. 20 μM Aβ42 (pH 7.4) was incubated in the presence of Cu²⁺/H₂O₂ (a, b, c) and compared to 20 μM Aβ42 in phosphate buffer alone (pH 7.4) (d, e, f). Assembly was monitored by electron microscopy after incubation for (a and d) zero hours, (b and e) 24 hours and (c and f) 48 hours. Both oxidized and control Aβ42 samples show oligomeric species at zero hour (a, d) and fibrils following 48 hour incubation (c, g). However, at 24 hours (b and f) fibrils were observed in non-oxidized conditions (f), but no fibrils were observed in oxidised conditions (b). The presence of dityrosine was detected using immunogold labeling using a dityrosine specific antibody that labeled oxidized fibrils (g) but not control fibrils (h).