Supercontracted spider dragline silk: a solid-state NMR study of the local structure

The local structure of supercontracted dragline silk from the spider Nephila madagascariensis was investigated by solid-state nuclear magnetic resonance. Two-dimensional (2D) spin-diffusion experiments did not show any significant conformational changes in short-range order (and the secondary structure of the protein) upon supercontraction. Our results are in accordance with the proposal by Vollrath et al. (Proc R Soc London B 1996;263:147-151) that urea-supercontraction does not alter the local structure of spider dragline silk fundamentally. However, significant differences in the dynamics of the polypeptide chain upon supercontraction are detected at room temperature. At low temperature, these dynamics are frozen out. In addition, the role of the solvent (water) in the silk is investigated in Nephila edulis. Mobile water is detected at temperatures significantly below the freezing point of bulk water.