Fig. 4: STFT determines the directionality of β-sheet alignment and the reciprocal of the periodicity of β-sheets.
From: Atypical β-strand insertion mediates the noncovalent cross-linking in amyloid aggregates
a The upper panel shows one typical binarized STM image for STFT analysis. Scale bar: 5 nm. In the STFT analysis, the window is placed at strictly defined positions, represented by a grid of red dots. Two arbitrary window positions are marked with red and green squares. The lower panel displays the PSD calculated in Cartesian coordinates for the images within the red and green windows. The black dots represent spectral features, where the radial distance (q) indicates the spatial frequency of the β-sheet arrangement, while the angular distance (θ) corresponds to the β-sheet orientation. b Heatmaps of the radial distance q and c angular distance θ of β-sheet arrangement in gal-3 225–250. d Distribution plots of normalized θ (θi−θmin) and e along with the distribution of q values obtained from the windows in the STM images. f Comparison of q values and normalized θ values obtained from STFT analysis of STM images for different samples, where the x-axis represents the CV of normalized θ values, the y-axis displays the CV of q values, the size of the circles represents the proportion of cross-β-strand linker in the aggregates, and different colors represent different samples, Gray dashed circle indicates absence of cross-β-strand linker in the sample. Source data are provided as a Source data file.
