title: Atomistic simulation of nanomechanical properties of Alzheimer's Abeta(1-40) amyloid fibrils under compressive and tensile loading.
abstract: In addition to being associated with severe degenerative diseases, amyloids show exceptional mechanical properties including great strength, sturdiness and elasticity. However, thus far physical models that explain these properties remain elusive, and our understanding of molecular deformation and failure mechanisms of individual amyloid fibrils is limited. Here we report a series of molecular dynamics simulations, carried out to analyze the mechanical response of two-fold symmetric Abeta(1-40) amyloid fibrils, twisted protein nanofilaments consisting of a H-bonded layered structure. We find a correlation of the mechanical behavior with chemical and nanostructural rearrangements of the fibril during compressive and tensile deformation, showing that the density of H-bonds varies linearly with the measured strain. Further, we find that both compressive and tensile deformation is coupled with torsional deformation, which is manifested in a strong variation of the interlayer twist angle that is found to be proportional to both the applied stress and measured strain. In both compression and tension we observe an increase of the Young's modulus from 2.34 GPa (for less than 0.1% strain in compression and 0.2% strain in tension), to 12.43 GPa for compression and 18.05 GPa for tension. The moduli at larger deformation are in good agreement with experimental data, where values in the range of 10-20 GPa have been reported. Our studies confirm that amyloids feature a very high stiffness, and elucidate the importance of the chemical and structural rearrangements of the fibrils during deformation.
authors.affiliation: Laboratory for Atomistic and Molecular Mechanics, Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave. Room 1-235A&B, Cambridge, MA, USA.
authors.forename: Raffaella
authors.initials: R
authors.lastname: Paparcone
authors.forename: Sinan
authors.initials: S
authors.lastname: Keten
authors.forename: Markus J
authors.initials: MJ
authors.lastname: Buehler
mesh_terms: D000595:Amino Acid Sequence; D016229:Amyloid beta-Peptides / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D001696:Biomechanical Phenomena; D019245:Compressive Strength; D055119:Elastic Modulus; D006801:Humans; D006860:Hydrogen Bonding; D066298:In Vitro Techniques; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D008969:Molecular Sequence Data; D036103:Nanotechnology; D010446:Peptide Fragments / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D013718:Tensile Strength
chemical_list: D016229:Amyloid beta-Peptides; D010446:Peptide Fragments; C078592:amyloid beta-protein (1-40)