Extended Data Fig. 4: 2D classification of minor morphological populations formed by rPrP94–178.
From: Cryo-EM structure of a human prion fibril with a hydrophobic, protease-resistant core
a, Stain-embedded, Proteinase K and sonication treated fibrils show several minor populations of ribbon-like polymorphs (white arrows), including wide filaments with regions that abruptly stop (red arrows). These morphologies remain a minor species after vitrification in 2 % SDS alongside the major twisted species (single example black arrow) (b) A 2D classification round selecting for minor species results in 2D classes that make up 29 % (75,860 segments) of total particles sorted into defined classes (c) with 2.1% of the total segments across major and minor populations (~6000 particles) being sorted into classes that resemble thick ribbons with columns of alternating electron dense and poor material (stars). Additional 2D classification of segments that did not sort into thick ribbon classes (d) revealed several classes containing high-resolution information, in some classes even revealing 4.8 Å strand separation. The 16 best looking classes are shown and make up 62 % (47,479 segments) of the particles shown in (c). 3D reconstruction of these filaments was unsuccessful. A magnified view of select classes from (c) and (d) show the range of fibril widths observed (e) Scalebar in (a) 200 nm, in (b) 50 nm.
