Skin-core morphology in spider flagelliform silk

摘要

Skin-core morphologies enhancing strength and toughness are known for many polymer fibers. The only known example for orb-weaving spiders are major ampullate silk (MaS) gland fibers composed of an amorphous skin-layer and a core of polypeptide chains reinforced by crystalline nanodomains with poly-Ala motifs. The capture section of orb-webs consists of radial, load-bearing MaS fibers and an elastic flagelliform silk spiral. Although originally considered to be amorphous, the presence of reinforcing polyglycine II nanodomains has now been established for several flagelliform fibers. We searched for nanoscale heterogeneities in flagelliform fibers by scanning X-ray nanodiffraction with submicrometer lateral resolution. Argiope bruennichi's flagelliform silk was found to be fully amorphous while a skin-core morphologie with a semicrystalline skin containing polyglycine II nanodomains and an amorphous core was observed for Araneus marmoreus.