Intermediate Filament Packing in α-Keratin of Echidna Quill

摘要

The swelling and associated physical behavior of wool α-keratin fibers when im- mersed in a solution of formic acid in water have given rise to a detailed model for hexagonal packing of the intermediate filaments in hard α-keratin. Low-angle syn- chrotron x-ray diffraction studies of the α-keratin fibers of dry and fully hydrated echidna quills not only provide extremely accurate measurements of the radii of the intermediate filaments and their center-to-center spacing, but also reveal the superpos- ition of two separate infinite lattices in the meridional direction, one the accepted infinite repeat length of α-keratin, 47.0±0.2 nm, and the other 62.6±0.2 nm.