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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 ?
In our previous works, a water-in-oil (W/O) emulsion solvent diffusion method has been used to prepare the polymer hollow microspheres of silk fibroin protein [4, 5]
Kaplan, "Silk fibroin microtubes for blood vessel engineering", Biomaterials.
It is reported that SF can be a random coil structure or two kinds of crystalline structures, Silk I and Silk II [32], Silk I is the metastable structure of fibroin obtained in the abdominal glands of B.
2008, "Biodegradable materials based on silk fibroin and keratin," Biomacromolecules, 9, pp.
The two proteins silkworms produce from their spinnerets are fibroin, which makes up the thread, and sericin, which glues together the fibroin strands that a silkworm produces.
Unique molecular architecture of silk fibroin in the waxmoth, Galleria mellonella.
Initial XT-I activity assays used deglycosylated cartilage proteoglycans or solutions of silk fibroin consisting of ~60% of the sequence repetition [(SGAGA).
Silk properties determined by gland specific expression of spider fibroin gene family.
Students built simple molecules such as alanine and ATP on their own but participated in teams to build a turn of double stranded DNA and sheets of silk fibroin.
We found that cocoons contain [sim]10% proline, 10% glycine and 10% serine, the approximate composition of silk fibroin which has a six residue repeat: glycine-serine-glycine-alanine-glycine-alanine.
Kanebo face cream claims to "effectively counteract all aspects of ageing" and it contains pure apricot essence and a silk fibroin derivative for ultra-smooth skin.