Insect silks

Nirmala, X., Kodrik, D., Zurovec, M. and Sehnal, F. (2001), Insect silk contains both a Kunitz-type and a unique Kazal-type proteinase inhibitor , Eur. J. Biochem. 

The silks of insects like the silkworm Bombyx mori have been mentioned several times in this chapter in fact, far more is known about the biochemistry, molecular biology and genetics of the silkworm than of any spider. There are many similarities between insect silks and spider silks, e.g. the predominance of amino acids with short side chains or the occurrence of some sequence motifs, which can help to understand the general principles involved in the generation of their material properties. Yet, there are also major differences that have to be taken into account. Most insect silks are used as cocoons or protective webs in larval stages and originate in labial glands [32]. In contrast. 

Silk materials are envisaged for various biomedical, cosmetic, and technical applications. These applications have been mainly based on silkworm silk [59, 103, 104]. Since spider and insect silks have several features in common, the established applications for silkworm silks are also conceivable for spider silk, bearing in mind that spider silk might provide additional outstanding properties. 

Tussah silk is derived from other insects. 

Secondary Structure. The silkworm cocoon and spider dragline silks are characterized as an antiparaHel P-pleated sheet wherein the polymer chain axis is parallel to the fiber axis. Other silks are known to form a-hehcal (bees, wasps, ants) or cross- P-sheet (many insects) stmctures. The cross-P-sheets are characterized by a polymer chain axis perpendicular to the fiber axis and a higher serine content. Most silks assume a range of different secondary stmctures during processing from soluble protein in the glands to insoluble spun fibers. 

Animals, including insects and other arthropods or brewing, fish, silk and leather industries Research and educational laboratories, pest control... 

The larvae of Bombyx mori, the cultivated moth from which most silk has long been and still is made, feed on leaves of mulberry trees. In addition to cultivated silk, small quantities of "wild silk," also known as nonmulberry silk, have been derived in many parts of the world from the cocoons of moths other than Bombyx mori. Table 90 lists wild silks and the insect species that produce them (Peigler 1993 Jolly et al. 1979). 

Proteolytic enzymes Animals, including insects and other arthropods or their larval forms Dusts from barley, oats, rye, wheat or maize, or Biological washing powders and the baking, brewing, fish, silk and leather industries Research and educational laboratories, pest control and fruit cultivation The baking or flour milling industry or on farms... 

Unlike parasitoids of other insect orders that have host-seeking larvae, most parasitic hymenoptera lay their eggs on, in, or very close to a host individual [11]. This requires the adult female to find a suitable host, often with the aid of chemical cues from host frass, pheromones, plant volatiles emitted upon host feeding or egg-deposition, silk, honeydew and other secretions. She may then chemically mark the host following oviposition to reduce superparasitism by herself or intra- and inter-specific insects [11]. 

One additional factor that comes into play in the overall chemistry of the communication system relates to chemical signals from host plants that can override the photoperiodic control of phermone production. With the com earworm, it was found that a volatile chemical signal from com silk, probably ethylene, was required by wild insects for stimulation of pheromone production (33). This signal probably interacts with controls on the photoperiodic release of PBAN. 

Silk proteins (spidroins in spiders and fibroins in Lepidoptera insects) are assembled into well-defined nanofibrillar architectures (Craig and Riekel, 2002 Eby et al., 1999 Inoue et al., 2000b, 2001 Li et al., 1994 Putthanarat et al, 2000 Vollrath et al., 1996). Spidroins and fibroins are largely constructed from two chemically distinct repetitive motifs or blocks (Table I), an insoluble crystalline block and a soluble less-crystalline block (Craig, 2003 Fedic et al., 2002 Hayashi and Lewis, 2000 Hayashi et al., 1999). The crystalline blocks are composed of short side-chained amino acids in highly repetitive sequences that give rise to /1-sheet structures. 

Nevertheless, despite our rapidly increasing knowledge about silk protein sequences, very little is known about the part played by gene design (Tatham and Shewry, 2000) in the stability and solubility of the prespun silk and in the final property of silk fibers across a wider variety of spiders and insects. 

In summary, the dynamics of the hierarchical interaction between silk proteins in solution suggest that spiders and insects are trading long range crystallinity for local conformational transitions, thus allowing the... 

Although spider and insect spinning silks are different and their silk types and functions diverse (Craig, 2003 Foelix, 1996), it is strongly... 

A trademark of amyloid fibrils is their cross-/ structure. This structure is the basis of the repetitive hydrogen-bonding extension of the fibril (Makin et al., 2005). Cross-/ structures are observed in the silk fibers of some insects (Geddes et al., 1968 Hepburn et al., 1979), although none are observed in spiders or lepidoptera (Craig, 1997). This absence has been explained by the possibility that cross-/ silks or a-silks may be converted into collinear /1-silks by stretching the fiber and an increased orientation-function correlated to the speed at which silk is formed (Riekel et al., 2000). 

Bini, E., Knight, D. P., and Kaplan, D. L. (2004). Mapping domain structures in silks from insects and spiders related to protein assembly./. Mol. Biol. 335, 27-40. 

Craig, C. L., and Riekel, C. (2002). Comparative architecture of silks, fibrous proteins and their encoding genes in insects and spiders. Comp. Biochem. Physiol. B Biochem. Mol. Biol. 133, 493-507. 

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