Fig. 3.

Native L. hesperus MA silk protein imaged by cryo-TEM (4 h incubation in 4 M urea) after shear (vigorous micropipette pumping). (A) Low-magnification images showing the abundance of generally spherical assemblies (100–300 nm). Insets highlight the small population of the largest assemblies found (∼500–800 nm) and a region found with isolated fibrils (Left inset). (Scale bar, 2 µm.) (B) High-magnification images of the spidroin assemblies, representative of the highest populations; spherical hierarchical assemblies composed of interwoven fibrillar subdomains. Insets show the smaller population of loosely packed fibrillar aggregates. (Scale bar, 200 nm.) (C–E) Cryo-TEM images from a tilt series of one selected hierarchical nanoassembly. (F) The 3D tomography rendering of the assembly in C–E. (G and H) Approximately 0.8-nm-thick z slices extracted at different z heights from the tomography reconstruction in F of the assembly in C–E.