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Differential polymerization of the two main protein components of dragline silk during fibre spinning


Spider silks are some of the strongest materials found in nature1,2. Achieving the high tensile strength and elasticity of the dragline of orb-weaving spiders, such as Nephila clavipes3,4,5, is a principal goal in biomimetics research. The dragline has a composite nature and is predominantly made up by two proteins, the major ampullate spidroins 1 and 2 (refs 37), which can be considered natural block copolymers8. On the basis of their molecular structures both spidroins are thought to contribute, in different ways, to the mechanical properties of dragline silk9. The spinning process itself is also considered important for determining the observed features by shaping the hierarchical structure of the fibre10,11. Here we study the heterogeneous distribution of proteins along the radial axis of the fibre. This heterogeneity is generated during the conversion of the liquid spinning dope into solid fibre. Whereas spidroin 1 is distributed almost uniformly within the fibre core, spidroin 2 is missing in the periphery and is tightly packed in certain core areas. Our findings suggest that the role of spidroin 2 in the spinning process could be to facilitate the formation of fibrils and contribute directly to the elasticity of the silk.

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Figure 1: Reactivity of spidroin 1 and 2 specific sera to duct cross-sections.
Figure 2: Reactivity of spidroin 1 and 2 specific sera to thread cross-sections.
Figure 3: Staining pattern of spidroin 1 and 2 specific sera within the thread core.


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The authors want to thank U. Stephan and K. Hartung for excellent technical assistance. This work was supported by Bundesministerium für Forschung und Bildung (BMBF FKZ 0311130), Bundesministerium für Landwirtschaft (BML FKZ 98NR049) and Thueringer Ministerium für Wissenschaft, Forschung und Kultur (TMWFK B307-99-001). A. Sponner was supported by an EU TOK grant (MTKD-CT-2004-014533).

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Correspondence to Klaus Weisshart.

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Sponner, A., Unger, E., Grosse, F. et al. Differential polymerization of the two main protein components of dragline silk during fibre spinning. Nature Mater 4, 772–775 (2005).

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