Beta transition and stress-induced phase separation in the spinning of spider dragline silk

Spider dragline silk is formed as the result of a remarkable transformation in which an aqueous dope solution is rapidly converted into an insoluble p rotein filament with outstanding mechanical properties. Microscopy on the s pinning duct in Nephila edulis spiders suggests that this transformation in volves a stress-induced formation of anti-parallel beta-sheets induced by e xtensional flow. Measurements of draw stress at different draw rates during silking confirm that a stress-induced phase transition occurs. (C) 2000 El sevier Science B.V. All rights reserved.