Figure 4

Structural features and population of Aβ42 aggregates at low concentration of DesBP. (a–c) Far-UV CD spectrum of 10 μM Aβ42 aggregates in absence (black) and presence (red) of 2.5 μM DesBP at three time points 0 (a), 4 (b), and 24 h (c). (d–i) Representative AFM images of Aβ42 in the absence of DesBP at different incubation times [0 (d), 4 (e) and 24 h (f)], and in the presence of 2.5 μM of DesBP at corresponding incubation times [0 (g), 4 (h) and 24 h (i)]. The scale bar on the AFM images indicate 1 μm and scale exhibited at the right represents the height. (j–m) Distribution of thickness (j) and length (l) and the mean values of height (k) and length (m) of fibrils at different time points (0, 4, and 24 h) formed in absence and presence of 2.5 μM determined by statistical analysis of AFM images. The n values in the histogram represent the number of fibrils used for AFM analysis. The symbols *, **, and ****p < 0.05, 0.01, 0.001, respectively. Fitted Gaussian curves are drawn as eye-guide in (j). Curves in (l) are fits with the log-normal distribution function (Eq. 1) and calculated mean values are represented with red bars in (m). Error bars of arithmetic averages of height (k) and length [black bars in (m)] represent STD and SEM, respectively. (n) MALDI mass spectrometry of aggregated contents. Samples were prepared at concentration of 5 μM Aβ42 with or without 20 μM DesBP. Aggregates are dissociated by 8 M Gdn-HCl at pH 8.0.