Aβ(25-35) aggregation on DOPC lipid bilayer.

<p>3×3 µm2 (a-c), and 5×5 µm2 (d-f), topographic AFM images (1024×1024px²) showing the time evolution of Aβ(25-35) on DOPC lipid bilayer. AFM measurements were performed in tapping mode and in PBS with a continuous scanning of the same area after the addition of the peptide. Over time, Aβ(25-35) forms layered aggregates (LA) on the bilayer surface, bilayer defect areas increase in size and Aβ(25-35) gradually covers the disrupted areas with disordered aggregates (DA). (g) Graph showing the increase in surface area covered by LA (blue line) and the evolution of lipid bilayer over time (red line). Data were qualitatively fitted by rational and sigmoidal functions for the DOPC bilayer (θDOPC) and the LA domains (θP), respectively. Fitting curves act as a guide-to-the-eye. (h) Height distribution histograms measured at t = 30 min (black), 1 h (red), 2 h (green), 3 h (blue), 4 h (cyan) and 5 h (magenta). The squared dashed-line in (e) indicates the area where statistical analyses on 5×5 µm2 AFM images were performed so as to keep the same scan size amongst images.</p

Aggregation of Aβ(25-35) on mica.

<p>Topographic AFM images of Aβ(25-35) aggregates grown on mica. Images were acquired in tapping mode and in PBS. (a) After 6 hours, Aβ(25-35) forms a smooth homogeneous layer without any well-formed aggregates (3×3 µm², 2459×2459px²). (b) On a smaller scale the peptide tends to organize into a texture with some discernible protrusions (white ellipse) (500×500 nm², 1228×1228px²).</p

DOPC and DOPC/DHA lipid bilayers.

<p>(a) Height AFM images of DOPC (2.5×2.5 µm² 1024×1024px²) and DOPC/DHA (b) (2.5×2.5 512×512px²) lipid bilayers performed in tapping mode and in PBS. The bilayers cover 92% (DOPC) and 96% (DOPC/DHA) of the mica surface. On DOPC lipid particles collected at the border or within defects are due to incomplete bilayer formation or to defective rinsing.</p

Aβ(25-35) aggregation on DOPC/DHA lipid bilayer.

<p>(a-c) 5×2.2 µm² (1024×431px²) topographic AFM images of Aβ(25-35) aggregation on DOPC/DHA lipid bilayers. (d) Graph showing the increasing surface area covered by LA (blue line) and the lipid bilayer evolution over time (red line). LA structures were grown within the first 30 min of peptide deposition while the lipid surface area decreased slowly from 96% to 91%. Data were qualitatively fitted by rational and sigmoidal functions for the DOPC/DHA bilayer (Θ_DOPC/DHA) and the LA domains (Θ_P), respectively. Fitting curves act as guide-to-the-eye. (e) Height distribution histograms measured at t = 0 min (black), 30 min (red), 1 h (green), 1 h45 min (blue), 2 h (cyan) and 2 h20 min (magenta).</p

Aβ(25-35) high resolution analysis.

<p>Topographic AFM images (a, c) and corresponding phase images (b, d) performed in PBS on the same area (360×360 nm², 1024×1024 px²) of Aβ(25-35) LA domains on the DOPC bilayer. Images were acquired with an average tip-sample force of 170pN by scanning from left to right (a, b) and from right to left (c, d). Topographies clearly show both globular aggregates (circled) and annular structures (squared). The complex LA aggregate (arrow) in the bottom right-hand corner and the globular aggregate in the top right-hand corner (insets) are perturbed by the tip movement. (e, f) Height (black) and phase (red) line profiles of globular (e) and annular structures (f) measured along the white dashed line in Fig. 6a and 6c. (g,h) Height images of a highly dense globular structure region (286×286 nm², 574×574px²) acquired with two different tip-sample forces. At 220 pN (g), the globular structures are not perturbed, while at 234 pN (h) they are mechanically removed leaving the underlying annular structures. (i, l) AFM height images (770×770 nm², 633×633 px²) of LA on two different regions of the DOPC/DHA bilayer. After 1 h45 min of peptide deposition (i) the LA presents a linear organization highlighted by grey fibres. After 2 h20 min (l) the LA forms a structured layer where linear organization is less visible though still distinguishable. In some locations, it is organized into annular structures (red circles) similar in dimension but more sporadic and of different nature compared to the ones observed on DOPC.</p