MOLECULAR-ORIENTATION AND 2-COMPONENT NATURE OF THE CRYSTALLINE FRACTION OF SPIDER DRAGLINE SILK

The molecular origin of the exceptional mechanical properties of spide r silk is unclear. This paper presents solid-state H-2 nuclear magneti c resonance data from unoriented, oriented, and supercontracted fibers , indicating that the crystalline fraction of dragline silk consists o f two types of alanine-rich regions, one that is highly oriented and o ne that is poorly oriented and less densely packed. A new model for th e molecular-level structure of individual silk molecules and their arr angement in the fibers is proposed. These data suggest that it will be necessary to control the secondary structure of individual polymer mo lecules in order to obtain optimum properties in bio-inspired polymers .