Tensile properties of synthetic pyriform spider silk fibers depend on the number of repetitive units as well as the presence of N- and C-terminal domains.

Spiders can spin seven different types of silk, some of which are well characterized, but studies on natural and synthetic pyriform silks are few. In this study, recombinant spidroins composed of one to three pyriform repeat units from Araneus ventricosus, in some cases flanked with non-repetitive N- and C-terminal domains (NT and CT), were produced and spun into continuous silk fibers using a wet-spinning process in organic solvents. All the fibers showed high and similar tensile strain (60-80%), but the Young's modulus, stress and toughness of fibers increased with increasing number of repeat units and in the presence of NT and CT as well. Systematic studies of the secondary structure contents of the different spinning dopes and spun fibers revealed no major differences between the different types of recombinant spidroins. This suggests that optimal tensile properties of artificial spider silks require the presence of several repetitive units as well as terminal domains and that secondary structure content of silk dope and fibers have limited correlation with mechanical behaviors.