title: Aggregation and fibril morphology of the Arctic mutation of Alzheimer's Aβ peptide by CD, TEM, STEM and in situ AFM.
abstract: Morphology of aggregation intermediates, polymorphism of amyloid fibrils and aggregation kinetics of the "Arctic" mutant of the Alzheimer's amyloid β-peptide, Aβ((1-40))(E22G), in a physiologically relevant Tris buffer (pH 7.4) were thoroughly explored in comparison with the human wild type Alzheimer's amyloid peptide, wt-Aβ((1-40)), using both in situ atomic force and electron microscopy, circular dichroism and thioflavin T fluorescence assays. For arc-Aβ((1-40)) at the end of the 'lag'-period of fibrillization an abrupt appearance of ≈ 3 nm size 'spherical aggregates' with a homogeneous morphology, was identified. Then, the aggregation proceeds with a rapid growth of amyloid fibrils with a variety of morphologies, while the spherical aggregates eventually disappeared during in situ measurements. Arc-Aβ((1-40)) was also shown to form fibrils at much lower concentrations than wt-Aβ((1-40)): ≤ 2.5 μM and 12.5 μM, respectively. Moreover, at the same concentration, 50 μM, the aggregation process proceeds more rapidly for arc-Aβ((1-40)): the first amyloid fibrils were observed after c.a. 72 h from the onset of incubation as compared to approximately 7 days for wt-Aβ((1-40)). Amyloid fibrils of arc-Aβ((1-40)) exhibit a large variety of polymorphs, at least five, both coiled and non-coiled distinct fibril structures were recognized by AFM, while at least four types of arc-Aβ((1-40)) fibrils were identified by TEM and STEM and their mass-per-length statistics were collected suggesting supramolecular structures with two, four and six β-sheet laminae. Our results suggest a pathway of fibrillogenesis for full-length Alzheimer's peptides with small and structurally ordered transient spherical aggregates as on-pathway immediate precursors of amyloid fibrils.
authors: Chemistry of Interfaces, Luleå University of Technology, SE-971 87 Luleå, Sweden.
authors: Nils
authors: N
authors: Norlin
authors: Magnus
authors: M
authors: Hellberg
authors: Andrei
authors: A
authors: Filippov
authors: Alioscka A
authors: AA
authors: Sousa
authors: Gerhard
authors: G
authors: Gröbner
authors: Richard D
authors: RD
authors: Leapman
authors: Nils
authors: N
authors: Almqvist
authors: Oleg N
authors: ON
authors: Antzutkin
mesh_terms: D000682:Amyloid / Q000737:chemistry* / Q000648:ultrastructure; D016229:Amyloid beta-Peptides / Q000737:chemistry* / Q000235:genetics / Q000648:ultrastructure; D002021:Buffers; D002942:Circular Dichroism; D006801:Humans; D007700:Kinetics; D018625:Microscopy, Atomic Force; D017348:Microscopy, Electron, Scanning Transmission; D008958:Models, Molecular; D020125:Mutation, Missense; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D059008:Time-Lapse Imaging
chemical_list: D000682:Amyloid; D016229:Amyloid beta-Peptides; D002021:Buffers