Figure 3.

Point mutations in Aβ(1–40) modulate aggregate morphology in the presence of a mica surface. Using solution AFM, the aggregation of Wild Type, Arctic (E22G), and Italian (E22K) Aβ was monitored on a mica surface (Aβ concentration was 20 μM for all experiments). 5 μm × 5 μm images are presented in 3D with indicated zoomed in areas of 1 μm × 1 μm shown in 2D. (A) Wild Type Aβ formed a large population of oligomers (red arrows) and highly curved, elongated protofibrils (yellow arrows) with aggregate heights of ∼3–5 nm similar to presented in Figure 2. (B) Arctic Aβ formed rigid, branched, and highly ordered fibrillar aggregates (blue arrows) along the crystallographic lattice of mica with aggregate heights of ∼2–5 nm along the contour. These Arctic Aβ aggregates morphologically distinct from those formed by Wild Type Aβ. (C) Italian Aβ predominately aggregated into small oligomers (2–3 nm tall, red arrows) that coalesced into larger protofibrils (yellow arrows), in a similar fashion to Wild Type Aβ; however, a small number of rigid, elongated “Arctic-like” fibrillar aggregates of Italian Aβ also formed (blue arrow).