Figure 8.

Aβ40 inhibits Aβ42 aggregation in vitro. Synthetic Aβ40 or Aβ42 peptides were mixed at various molar ratios (1:1.5 and 0.5:0.75 μm). Aβ mixtures were either directly used for analysis (indicated by “−”) or incubated for 2 h at 37°C (indicated by “=”) and electrophoresed on 4–20% Tris-HCl gels under nondenaturing conditions. The blot was probed with Ab9. After a 2 h incubation, the Aβ42-only preparation (Aβ40:Aβ42 ratio; 0:1) formed very high molecular weight (HMW) aggregates (indicated by “⇐” at the top of blot) without any low molecular weight LMW species, whereas the Aβ40 only preparation (Aβ40:Aβ42 ratio; 1:0) remained as a LMW species (indicated by ← at the bottom of blot). When Aβ40 was mixed with Aβ42 (Aβ40:Aβ42 ratio; 0.5:1 and 1:1), Aβ40 inhibited the formation of HMW Aβ42 aggregates, and the vast majority of Aβ42 remained as LMW species (indicated by ← at the bottom of the blot).