Regensburg 2010 – scientific programme

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SYMR: Symposium Nuclear Magnetic Resonance: from Applications in Condensed-Matter Physics to New Frontiers

SYMR 7: Biopolymers and Biomaterials

SYMR 7.4: Talk

Wednesday, March 24, 2010, 15:00–15:15, H37

SANS on Silkworm Silk under Tensile Stress — •Malte Blankenburg, Martin Müller, and Melissa Sharp — GKSS Research Centre Geesthacht, Germany

Natural silks exhibit extraordinary mechanical properties, combining high tensile strength with a high elongation at failure. Due to their remarkable mechanical properties and potential medical applications the ability to synthesize silk is still a matter of debate. Silkworm silk fibroin is a semicrystalline nanocomposite, with ordered regions (β-sheet protein nanocrystals) embedded in a softer, amorphous matrix of disordered material [1]. Therefore the contrast between matrix and crystallites could be improved for neutron experiments by deuterating the silk. SANS experiments performed in situ during tensile stretching experiments at the SANS-2 instrument at the GKSS showed a peak in the meridional direction of the scattering pattern of deuterated silkworm silk. Since this peak moves to lower q-values by stretching the fibres, an enlargement of the scattering structure could be observed. It was shown before in X-ray experiments [2], that the crystals in the matrix are stretched proportionally to the applied external tensile stress but by a factor of 4 to 18 less than the macroscopic strain. As the percentage elongation is nearly the same for fibre and scattering structure, the scattering objects are not the crystals but rather the ensemble of crystals and disordered material in a periodic arrangement, reflecting the mean distance between crystals in fibre direction.

[1] Y. Shen et al.; Macromolecules 31 (1998), 8857

[2] I. Krasnov et al.; Phys. Rev. Lett. 100 (2008), 048104