Figure 4. Morphological comparison of Aβ(1–40) and Aβ(1–40)E22G.

Contact mode AFM images (5 µm × 5 µm, Z scale 15 nm) of Aβ(1–40) and Aβ(1–40)E22G peptides on mica, recorded either in phosphate buffer or in MOPS buffer with Ca²⁺. Samples of Aβ(1–40) and Aβ(1–40)E22G in the presence and absence of added Ca²⁺ (marked as “+Ca²⁺” or “−Ca²⁺”, respectively) at t = 0, 6, or 72 h. Closer views (1 µm × 1 µm, Z scale 15 nm) of oligomers, protofibrils and fibrils are shown as insets in the panel of t = 72 h (C, F, I, L). Images A, D, G, J were taken at t = 0; images B, E, H, K were taken at t = 6 h. Peptide concentration was the same in all samples.