title: Self-assembly in aqueous solution of a modified amyloid beta peptide fragment.
abstract: The self-assembly in films dried from aqueous solutions of a modified amyloid beta peptide fragment is studied. We focus on sequence Abeta(16-20), KLVFF, extended by two alanines at the N-terminus to give AAKLVFF. Self-assembly into twisted ribbon fibrils is observed, as confirmed by transmission electron microscopy (TEM). Dynamic light scattering reveals the semi-flexible nature of the AAKLVFF fibrils, while polarized optical microscopy shows that the peptide fibrils crystallize after an aqueous solution of AAKLVFF is matured over 5 days. The secondary structure of the fibrils is studied by FT-IR, circular dichroism and X-ray diffraction (XRD), which provide evidence for beta-sheet structure in the fibril. From high resolution TEM it is concluded that the average width of an AAKLVFF fibril is (63+/-18) nm, indicating that these fibrils comprise beta-sheets with multiple repeats of the unit cell, determined by XRD to have b and c dimensions 1.9 and 4.4 nm with an a axis 0.96 nm, corresponding to twice the peptide backbone spacing in the antiparallel beta-sheet.
authors.affiliation: Department of Chemistry, The University of Reading, Reading RG66AD, UK.
authors.forename: V
authors.initials: V
authors.lastname: Castelletto
authors.forename: I W
authors.initials: IW
authors.lastname: Hamley
authors.forename: P J F
authors.initials: PJ
authors.lastname: Harris
mesh_terms: D016229:Amyloid beta-Peptides / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure*; D006801:Humans; D046529:Microscopy, Electron, Transmission; D010446:Peptide Fragments / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure*; D017433:Protein Structure, Secondary; D017550:Spectroscopy, Fourier Transform Infrared; D014961:X-Ray Diffraction
chemical_list: D016229:Amyloid beta-Peptides; D010446:Peptide Fragments