Altering the mechanics of spider silk through methanol post-spin drawing

Spiders have evolved to produce up to seven different silks; for each silk the balance between strength and elasticity is optimized according to the silk's specific use. Amino acid motifs have been identified and predicted functions have been assigned to these motifs. In addition to understanding the underlying molecular basis for structure/function relationships, it is also necessary to understand the contribution of the spinning process to the overall mechanical properties for both native and synthetic silk fibers. It is hypothesized that the natural silk fiber is produced through a process that involves dehydration. Current artificial spinning methods attempt to reproduce the natural dehydrating conditions by pulling the newly formed fiber through a methanol (or other dehydrating solvent) bath. However, the consequences of this treatment on the mechanical properties of the artificial fiber in relation to the natural fiber are unknown. To evaluate the effect of methanol on fiber properties, mechanical testing was done on native fibers from Nephila clavipes. Single major ampullate fibers were spun either in 47% ambient humidity or drawn post-spinning through a methanol bath. A comparison of the mechanical properties of the silk fibers revealed that post-spin drawing of a single major ampullate silk fiber through a methanol bath correlates to changes in the mechanical properties of the fiber.