Structure and Texture of Fibrous Crystals Formed by Alzheimer's Aβ(11–25) Peptide Fragment

AbstractAmyloid fibril deposition is central to the pathology of Alzheimer's disease. X-ray diffraction from amyloid fibrils formed from full-length Aβ(1–40) and from a shorter fragment, Aβ(11–25), have revealed cross-β diffraction fingerprints. Magnetic alignment of Aβ(11–25) amyloid fibrils gave a distinctive X-ray diffraction texture, allowing interpretation of the diffraction data and a model of the arrangement of the peptides within the amyloid fiber specimen to be constructed. An intriguing feature of the structure of fibrillar Aβ(11–25) is that the β sheets, of width 5.2 nm, stack by slipping relative to each other by the length of two amino acid units (0.70 nm) to form β ribbons 4.42 nm in thickness. Aβ(1–40) amyloid fibrils likely consist of once-folded hairpins, consistent with the size of the fibers obtained using electron microscopy and X-ray diffraction