Silk Polymer Designs for Improved Expression and Processing

Silk fibers formed by insects and spiders are noted for their remarkable mechanical properties as well as their durability and biocompatibility. The exceptional solubility in vivo (20-30% w/v) of these proteins is dictated by both the need to produce solid fibers with a high packing fraction and the high mesogen concentration required for lyotropic liquid crystalline spinning, while also achieving high end mechanical properties for survival (orb webs, cocoons). Combining knowledge of the solution state behavior, protein folding requirements and silk genetic/protein designs employing complex block- copolymer attributes, offers new experimental directions. Our objective was to determine the relationships between genetic/protein block designs coupled with the limitations imposed by an all aqueous processing environment. The significance of the studies was that by employing these design rules there should be improved expression, recovery of soluble protein and control of processing into high solids solutions and gels leading to spinnable dopes for fibers, films or other material outcomes. The insights from the studies have implications in fundamental structural biology as well as direct utility toward improved options in silk-based polymer synthesis, processing and materials fabrication.