Recombinant Pyriform Silk Fiber Mechanics Are Modulated by Wet-Spinning Conditions.

Pyriform silk is a critically important fiber in spider web construction. It functions in a glue-coated attachment disc to form junctions in spider webs, connecting the web to disparate materials. Despite the biological importance of this silk, both natural and recombinant pyriform silk have yet to be structurally or mechanically characterized. In this study, we demonstrate recombinant production of a 477 amino acid protein based on Argiope argentata pyriform silk. This pyriform silk protein shows α-helicity in both an aqueous buffer and in a fluorinated acid- and alcohol-based spinning dope. Wet-spinning produced fibers having no visible defects in surface or cross-sectional analysis, with mechanical behavior varying as a function of postspin stretching conditions and correlating to loss of α-helicity in the fibrous state. Multiple conditions gave rise to fibers that are both strong and extensible, contrasting with some other silks that are biased toward being strong or extensible. This behavior is strikingly similar to recombinant aciniform silk, despite distinct primary structuring and composition.