Explanation for the mechanical strength of amyloid fibrils

Abstract

The presence of ''proteinaceous b-sheet rich fibrillar structures'' and amyloidogenic material, has been alluded to extensively in the literature, in association with natural materials exhibiting superior mechanical strength per unit volume. Here we provide a clear experimental demonstration and explanation for why individual amyloid quaternary structures themselves have beneficial mechanical characteristics.

Biophysical characterization of alpha-synuclein aggregates : Parkinson's disease at the nanoscale

“…This same effect was found for Aβ 1−42 fibrils (Arimon et al, 2005). Fibrils may be damaged by forces as low as 100 pN during imaging in contact mode in air (Fukuma et al, 2006). Other authors indicate fibrils are damaged by indentation forces ranging from 40 − 100 nN .…”

“…Amyloid fibrils can be used as structuring agents in foods (van der Linden and Venema, 2007) and as new nanomaterials for potential use in nanotechnology applications (Knowles et al, 2007). Nature itself uses amyloid fibrils as a building material as well, as evidenced by the presence of amyloid fibrils in an adhesive secreted by an alga (Mostaert et al, 2006). The strength that non-pathogenic amyloid fibrils provide to composite materials makes them nature's version of the carbon nanotube (Mostaert and Jarvis, 2007).…”

“…Non-specific adhesion of the tip to the fibril may 'mechanically unzip' filaments from the fibrils (Fukuma et al, 2006;. When force-distance curves are recorded on every pixel in a raster pattern, a so-called force-volume image or adhesion image is made .…”

“…In experiments where TTR 105−115 fibrils were 'unzipped' mechanically by pulling with an AFM tip, a sawtooth pattern in the extension curve indicates a sequential breaking of β-strands from the intermolecular β-sheet at a force of 20 pN (Fukuma et al, 2006). This process of breaking of a material in steps, by removal of so-called 'sacrificial bonds' revealing 'hidden length', is a mechanism that applies to many materials with high macroscopic mechanical tensile strength (Fukuma et al, 2006). These authors even speculate that the selfassembling nature of amyloid fibrils allows them to self-heal under appropriate conditions, which if true would make amyloid fibrils even more interesting as a nanomaterial.…”

“…These authors even speculate that the selfassembling nature of amyloid fibrils allows them to self-heal under appropriate conditions, which if true would make amyloid fibrils even more interesting as a nanomaterial. Amyloid fibrils appearing in other settings, such as in a natural adhesive secreted by an alga, also show force plateaus indicative of mechanical unzipping of fibrils, and large number of unfolding events indicating the fibrils consist of cross-linked proteins (Mostaert et al, 2006). Molecular dynamics simulations have shown that Aβ dissociation is highly anisotropic: Aβ fibrils are strong but brittle when pulled perpendicular to the fibril axis, and less strong but soft when pulled along the fibril length (Raman et al, 2007).…”