Abstract

Silks are naturally spun fibrous proteins most often associated with the silkworm and spiders. Silk fibers are unusual in combining strength, toughness, and compressibility. The proteins are characterized primarily by a -sheet secondary structure consisting of a highly crystalline region as well as regions of lower crystallinity. Silkworm cocoon fibers have been used in textiles for thousands of years. Spider silk, of which there are many different types, has not been domesticated. Water-soluble silk proteins are synthesized and stored in the silk glands until spun into fibers, at which point they become insoluble in water. The spinning process is regulated by the organism and involves the extrusion of the soluble silk in a liquid crystalline state through spinnerets. Silks are stable to approximately 230°C. Membranes have been formed from silks that provide a useful means to explore secondary structure and to entrap enzymes. Worldwide production of silkworm silk for textiles is expected to increase. Future applications depend on the success of biotechnology to provide adequate production levels of specifically tailored silk compositions.