X-ray diffraction study of nanocrystalline and amorphous structure within major and minor ampullate dragline spider silks.

Synchrotron X-ray micro-diffraction experiments were carried out on (NC) and (AA) major (MA) and minor ampullate (MiA) fibers that make up dragline spider silk. The diffraction patterns show a semi-crystalline structure with β-poly(l-alanine) nanocrystallites embedded in a partially oriented amorphous matrix. A superlattice reflection 'S' diffraction ring is observed, which corresponds to a crystalline component larger in size and is poorly oriented, when compared to the β-poly(l-alanine) nanocrystallites that are commonly observed in dragline spider silks.