Characterization of the nanoscale properties of individual amyloid fibrils

Abstract

We report the detailed mechanical characterization of individual amyloid fibrils by atomic force microscopy and spectroscopy. These self-assembling materials, formed here from the protein insulin, were shown to have a strength of 0.6 ؎ 0.4 GPa, comparable to that of steel (0.6 -1.8 GPa), and a mechanical stiffness, as measured by Young's modulus, of 3.3 ؎ 0.4 GPa, comparable to that of silk (1-10 GPa). The values of these parameters reveal that the fibrils possess properties that make these structures highly attractive for future technological applications. In addition, analysis of the solutionstate growth kinetics indicated a breakage rate constant of 1.7 ؎ 1.3 ؋ 10 ؊8 s ؊1 , which reveals that a fibril 10 m in length breaks spontaneously on average every 47 min, suggesting that internal fracturing is likely to be of fundamental importance in the proliferation of amyloid fibrils and therefore for understanding the progression of their associated pathogenic disorders.atomic force microscopy ͉ force spectroscopy ͉ nanotechnology ͉ prions ͉ protein aggregation

Hierarchical Structure and Nanomechanics of Collagen Microfibrils from the Atomistic Scale Up

“…This suggests that in the dry microfibril the deformation mechanism initially involves primarily the straightening of the collagen molecules and not stretching of the molecules itself (this is confirmed by the observation that the end-to-end distance at 200 MPa stress is 260 nm, much shorter than the collagen molecules' contour length). The analysis of the gap/overlap ratio (red, panel c) shows that the deformation is initially distributed in both the gap and [71][72][73][74][75]. However, most of the protein materials feature Young's moduli in the range of 100 MPa to 10 GPa, well below the stiffness of many synthetic nanostructured material such as carbon nanotubes.…”

A polymer physics perspective on driving forces and mechanisms for protein aggregation

“…Additionally, as Wu and coworkers have demonstrated, the use of scattering-based techniques [73], including X-ray / neutron scattering and light scattering, combined with theory and simulation should be very useful in the study of aggregation-prone IDPs. Several groups in the amyloid field are already pursuing these types of multi-faceted approaches [5,84,[94][95][96][97][98][99][100][101][102][103][104][105][106][107]. However, we remain blind to interactions and conformational fluctuations that occur at low concentrations.…”

Quantitative approaches to defining normal and aberrant protein homeostasis

“…[35][36][37][38] (2) New ideas about protein aggregation, 10,28 including the finding that the ability to assemble into stable and highly organised structures (e.g. amyloid fibrils) is not an unusual feature exhibited by a small group of peptides and proteins with special sequence or structural properties, but rather a property shared by most, if not all, proteins; (3) The discovery that specific aspects of protein behaviour, including their aggregation propensities 21,23,39,40 and the cellular toxicity associated with the aggregation process, 24,41 can be predicted with a remarkable degree of accuracy from the knowledge of their amino acid sequences; (4) The realisation that a wide variety of techniques originally devised for applications in nanotechnology can be used to probe the nature of protein aggregation and assembly and of the structures that emerge; 30,[42][43][44] and (5) The development of powerful approaches using model organisms for probing the origins and progression of misfolding diseases by linking concepts and principles emerging from in vitro studies to in vivo phenomena such as neurodegeneration. 24 An analysis of these results, which span across a wide range of subjects from neuroscience to nanoscience, reveals that the ability to keep proteins in their soluble form is absolutely central for the maintenance of cell homeostasis.…”

“…Powerful techniques are being developed to complement more established methods to overcome the challenges posed by the task of providing such a description. 30,[42][43][44]46 Our own approach is based primarily on methods that directly combine experimental and computational techniques. 5,6,35 These procedures involve the use of experimental data, largely derived from NMR spectroscopy, as restraints in computer simulations.…”

“…[70][71][72] Together with the strategy mentioned above, nanoscience techniques are also emerging as powerful tools that can provide insight into the factors that stabilise amyloid fibrils. 30,42,44 In an initial study, by using atomic force microscopy (AFM) imaging we described the changes in the distribution of inter-versus intra-molecular bonding interactions associated with the transition of proteins from their native globular structures into ordered supramolecular assemblies. This work reveals that hydrogen bonded arrays of polypeptide chains exhibit material properties intermediate between those of hard materials such as steel and carbon nanotubes and softer biological fibres such as tubulin and actin (Fig.…”