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. Author manuscript; available in PMC: 2013 Dec 1.
Published in final edited form as: Ultramicroscopy. 2012 May 18;123:38–49. doi: 10.1016/j.ultramic.2012.04.005

Figure 2.

Figure 2

Figure 2

Figure 2

Figure 2

STEM mass measurement of amyloid fibrils formed by the Alzheimer’s β-amyloid peptide (Aβ) and the HET-s prion protein. (A) Annular dark-field STEM image of Aβ (1-40) fibrils, with tobacco mosaic virus (TMV) included for mass calibration. (B) Mass-per-length (MPL) histogram indicating that fibrils are constructed from three Aβ (1-40) molecules per cross-β repeat (0.47 nm), lending support to a threefold symmetric structure. Adapted from Paravastu et al., 2008 [26]. (C–F) STEM images of HET-s (218–289) (C) and HET-s (157–289) (E) with corresponding MPL distributions (D,F). Values of MPL are consistent with a fibril packing density of 0.5 of a subunit per 0.47 nm. The brighter straight rods are TMV particles. Scale bar, 100 nm. Adapted from Sen et al., 2007 [25], with permission from The American Society for Biochemistry and Molecular Biology.