Spider silk is “pound for pound” stronger than steel and has a greater elasticity than rubber. Such properties would make it a rather useful material for a large variety of medical and engineering applications if only it could be made in large enough quantities and with a useful thickness and consistency.
Thomas Scheibel at the Technical University of Munich has now taken a step towards understanding the spider’s secret with a view to creating an artificial spinneret for producing unlimited quantities of spider silk. Writing in in Angewandte, the team explain how they have discovered that the interaction between the hydrophilic and lipophilic properties of the silk proteins plays an important role in the spinning process.
Fundamentally, the spinning of spider silk represents a phase change from a solution into a solid thread. The silk used by orb weaver spiders to spin the edges and spokes of their webs and to make a quick escape when attacked is composed of two different proteins. The Munich team has now successfully used genetic engineering to produce one of the spider silk proteins of the European garden spider (Araneus daidematus).
While purifying the protein by dialysis, the researchers observed the separation of two different fluid phases. Whereas one phase consisted of protein dimers, the second consisted of oligomers. After adding potassium phosphate, a natural initiator of silk aggregation, the liquid could be pulled into threads. “It is clearly not a structural change in the protein, but rather the degree of oligomerization that is crucial for thread formation,” concludes Scheibel.