Fig. 2.

Native L. hesperus MA silk protein imaged by cryo-TEM (4 h incubation in 4 M urea). (A) Low-magnification image showing abundance of generally spherical (200–400 nm) micellar protein assemblies. Insets highlight the small population of the largest assemblies found (∼500–800 nm). (Scale bar, 2 µm.) (B) High-magnification images of the spidroin hierarchical assemblies, representative of the highest populations; spherical micellar assemblies composed of disordered flake-like subdomains. Black boxed Inset shows similar structures found in a sample prepared from a separate spider following the same procedure (SI Appendix, Fig. S4). (Scale bar for Insets, 200 nm.) (C–E) Cryo-TEM images from a tomography tilt series of one selected hierarchical protein nanoassembly. (F) The 3D isosurface 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.