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A protein secreted by spiders and silkworms which rapidly solidifies into strong, insoluble thread that is used to form webs or cocoons.



a simple protein, the principal component of the natural silk and spider-silk fibers secreted by the silk-secreting glands of certain insects and the silk glands of spiders and other arthropods. Fibroin is a viscous, syrupy fluid, that hardens in the air to a tough, insoluble filament. Fibroin threads, coated with the protein sericin, form a silk fiber, as in silkworm cocoons.

Fibroin belongs to a group of structural proteins called scleroproteins. It is resistant to organic solvents, dilute acids and bases, and proteolytic enzymes. The fibroin molecule consists of an elongated polypeptide chaino with repeating structural units, measuring approximately 7 Å. The group of amino acids in fibroin includes a high content of glycine (43 percent), alanine, serine, and tyrosine. The content of the amino acid tyrosine in fibroin is so much higher than in other proteins that fibroin is usually used as the prime source for obtaining tyrosine.

References in periodicals archive ?
mori silk fibroin with poly(ethylene oxide)," Biomacromolecules, 5, pp.
2010, "Silk fibroin encapsulated powder reservoirs for sustained release of adenosine," J.
Silk fibroin (SF), a structural protein has been studied and applied.
2006, "Time-resolved structural investigation of regenerated silk fibroin nanofibers treated with solvent vapor," Int.
2007, "Structure and properties of regenerated Antheraea pernyi silk fibroin in aqueous solution," Int.
2004, "Effect of chitosan on morphology and conformation of electrospun silk fibroin nanofibers," Polymer, 45, pp.