| Silk is an exceptionally strong, extensible and tough material made from simple protein building blocks. The molecular structure of dragline spider silk repeat units consists of semi-amorphous and nanocrystalline beta-sheet protein domains. Here we show by a series of computational experiments how the nanoscale properties of silk repeat units are scaled up to create macroscopic silk fibers with outstanding mechanical properties despite the presence of cavities, tears and cracks. We demonstrate that the geometric confinement of silk fibrils to diameters of 50±30 nm width is critical to facilitate a powerful mechanism by which hundreds of thousands of protein domains synergistically resist deformation and failure to provide enhanced strength,... |
