Small-Angle X-ray Scattering of Spider Dragline Silk

Abstract

As part of a general study of the structure of spider silk fibers, major ampullate gland silk fibers were collected from Nephila clavipes spiders, and SAXS patterns were obtained from loops of fibers under a variety of conditions. Two orders of lamellar reflection were seen, with a long spacing of 8.4 nm. This increased reversibly by 4% when the fiber was stretched by 10% and shrank to 5.8 nm when the fiber itself shrank 45% on wetting. A strong equatorial streak had a bimodal orientation distribution similar to that seen in NMR and WAXD. The sharper component had a lateral size scale (radius of gyration) of 2.5 nm and a misorientation of 10° FWHM, similar to the orientation of the crystals. The minimum breadth of the streak indicates that the scattering objects are 0.1 μm long. There is an isotropic central scattering, probably caused by voids. On wetting, the lamellar peaks became more intense; more dramatically, the equatorial scattering strengthens and extends to higher angles, almost halving the lateral size scale to 1.4 nm. An equatorial maximum appears at a spacing of 6 nm, indicating a degree of order in the fibrillar structure.

Structural evolution of regenerated silk fibroin under shear: Combined wide‐ and small‐angle x‐ray scattering experiments using synchrotron radiation

“…The 7.1 nm meridional peak in pattern C 4 is similar to the meridional peak found for Nephila major ampullate silk. 18,51 We do not, however, observe the characteristic two-point pattern, which is characteristic for a nanofibrillar system with a lamellar morphology. The azimuthal width of the low-angle meridional peak (e.g., C 1 in Figure 9) is rather similar to that of the equatorial reflections, which suggests that the peak is due to a c-axis lattice reflection.…”

The effect of proline on the network structure of major ampullate silks as inferred from their mechanical and optical properties

“…These crystals have been shown to be strongly aligned with the fibre axis and to occupy about 10-15% of the total volume of the fibre (Fornes et al, 1983;Grubb and Jelinski, 1997;Yang et al, 1997). These conclusions have been subsequently confirmed by nuclear magnetic resonance (NMR) (Simmons et al, 1996;Kummerlen et al, 1996) and Raman spectroscopy studies (Shoa et al, 1999;Edwards et al, 1995).…”

Structural characterization of a variety of spider silks from Turkey using different biophysical techniques

“…DLS (dynamic light scattering) and SAXS (small angle X-ray scattering) methods are useful to know more about nano-aggregations, present in silk structure [13,19,32,45]. Natural silk forms and their solutions may be analyzed by using these complementary experimental methods.…”