Albeit silks are fairly well understood on a molecular level, their hierarchical organisation and the full complexity of constituents in the spun fibre remain poorly defined. Here we link morphological defined structural elements in dragline silk of Nephila clavipes to their biochemical composition and physicochemical properties. Five layers of different make-ups could be distinguished. Of these only the two core layers contained the known silk proteins, but all can vitally contribute to the mechanical performance or properties of the silk fibre. Understanding the composite nature of silk and its supra-molecular organisation will open avenues in the production of high performance fibres based on artificially spun silk material.

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It has been confirmed that taxol is able to prevent Ca2+‐induced inhibition of microtubule formation from tubulin in the presence of microtubule‐associated proteins. However, by means of electron microscopy and scanning force microscopy it could be demonstrated that assembly in the presence of Ca2+ and taxol leads to structural aberrations. The kind of aberration depends on the order of addition of taxol and Ca2+ to tubulin. When taxol was added first, microtubules were formed preferentially. But, these microtubules typically associated with each other by close wall‐to‐wall alignments or they formed complexes with some C‐shaped protofilament ribbons, resulting in microtubule bundles or doublet‐and triplet‐like microtubule structures, respectively. When Ca2+ was added first, macrotubules, rings, and ring crystals were the dominant assembly products. Mostly, the macrotubules were also bundled or they enclosed rings in their lumen. The findings clearly demonstrate the potency of Ca2+ to induce different polymorphic assemblies with additional protofilament associations, not realized in microtubules. Cell Motil Cytoskeleton 36:76–83, 1997. © 1997 Wiley‐Liss, Inc.