Failure of Alzheimer's Aβ(1-40) amyloid nanofibrils under compressive loading

Amyloids are associated with severe degenerative diseases and show exceptional mechanical properties, in particular great stiffhess. Amyloid fibrils, forming protein nanotube structures, are elongated fibers with a diameter of a parts per thousand 8 nm with a characteristic dense hydrogen-bond (H-bond)patterning in the form of beta-sheets (beta-sheets). Here we report a series of molecular dynamics simulations to study mechanical failure properties of a twofold symmetric A beta(l-40) amyloid fibril, a pathogen associated with Alzheimer's disease. We carry out computational experiments to study the response of the amyloid fibril to compressive loading. Our investigations reveal atomistic details of the failure process, and confirm that the breakdown of H-bonds plays a critical role during the failure process of amyloid fibrils. We obtain a Young's modulus of a parts per thousand 12.43 GPa, in dose agreement with earlier experimental results. Our simulations show that failure by buck-ling and subsequent shearing in one of the layers initiates at a parts per thousand 1% compressive strain, suggesting that amyloid fibrils can be rather brittle mechanical elements.