The primary structure is mostly made of glycine and alanine. Silks are often called block copolymers because it consists of blocks of glycine and alanine. Alanines are mainly found in beta sheets of the nanofibril while glycine is mostly found in helical and beta turn structures. Silk is unlike any material due to the combined qualities of hard crystalline segments and elastic amorphous regions.
Also, silk filament derived from silkworm Bombyx mori is composed mainly of sericin and fibroin proteins. A really cool technique currently being developed is called electrospinning whereby an electrical charge is used to form very thin fibers from a liquid.
SEM images of pure silk
http://www.intechopen.com/books/advances-in-nanofibers/fabrication-of-nanofibrous-scaffolds-by-electrospinning
If only we could produce such efficient, flexible, strong materials as well as nature! The symmetry and functionality is really incredible!
Thanks for sharing, and especially for including images! It’s really amazing what nature can do…