http://orion.bme.columbia.edu/lulab/pdf/Altman_Silk-Based-Biomaterials_2003.pdf

Silk-based biomaterials

Spider silk has outstanding mechanical properties despite being spun at close to ambient temperatures and pressures using water as the solvent. The spider achieves this feat of benign fibre processing by judiciously controlling the folding and crystallization of the main protein constituents, and by adding auxiliary compounds, to create a composite material of defined hierarchical structure. Because the 'spinning dope' (the material from which silk is spun) is liquid crystalline, spiders can draw it during extrusion into a hardened fibre using minimal forces. This process involves an unusual internal drawdown within the spider's spinneret that is not seen in industrial fibre processing, followed by a conventional external drawdown after the dope has left the spinneret. Successful copying of the spider's internal processing and precise control over protein folding, combined with knowledge of the gene sequences of its spinning dopes, could permit industrial production of silk-based fibres with unique properties under benign conditions.

/pdf/liquid-crystalline-spinning-of-spider-silk-1li41hra2c.pdf

Liquid crystalline spinning of spider silk.

Hypotheses that correlate the sequence, structure, and mechanical properties of spider silk proteins.

The design principles of spider dragline silk, nature's high-performance fiber, are still largely unknown, in particular for the noncrystalline glycine-rich domains, which form the bulk of the material. Here we apply two-dimensional solid-state NMR to determine the distribution of the backbone torsion angles (φ,ψ) as well as the orientation of the polypeptide backbone toward the fiber at both the glycine and alanine residues. Instead of an “amorphous matrix,” suggested earlier for the glycine-rich domains, these new data indicate that all domains in dragline silk have a preferred secondary structure and are strongly oriented, with the chains predominantly parallel to the fiber. As proposed previously, the alanine residues are predominantly found in a β sheet conformation. The glycine residues are partly incorporated into the β sheets and otherwise form helical structures with an approximate 3-fold symmetry.

https://www.pnas.org/content/pnas/99/16/10266.full.pdf

The molecular structure of spider dragline silk: Folding and orientation of the protein backbone

Evidence from flagelliform silk cDNA for the structural basis of elasticity and modular nature of spider silks

The local structure of dragline silk from the spider Nephila madagascariensis is investigated by solid-state nuclear magnetic resonance. Two-dimensional (2D) spin-diffusion experiments show that th...

/pdf/local-structure-in-spider-dragline-silk-investigated-by-two-3hera1cbfl.pdf

J. Kümmerlen

Papers

Local Structure in Spider Dragline Silk Investigated by Two-Dimensional Spin-Diffusion Nuclear Magnetic Resonance†