Moth, silk

Plant fibers are cellulosic, animal fibers are proteinaceous materials, and asbestos is a crystalline silica compound. Almost every fibrous material has had some use in historic or prehistoric times. The most important natural fibers used in the textile industry are cotton, linen, wool, and silk (moth silk) (see Table 1). 

Cotton Kapok Akon Linen Hemp Jute Ramie Kenaf Sisal Manila hemp Yukka Banana Coco Sheep Alpaca Lama Vicunja Guanaco Camel Angora Mohair Cashmere Yak Cattle Horse Goat Moth silk Spider silk Mussel silk Asbestos... 

Weseloh, R. M. (1977) Behavioral responses of the parasite, Apanteles melanosceluSy to Gypsy moth silk. Env. Ent., 5, 1128-32. 

Bombykol (50), pheromone of the silk moth and the first whose structure was elucidated, can be made by two successive Wittig reactions, each giving the right geometry. Can you find this route ... 

Silk. Silk, the only natural fiber that comes in filament form, has been and still is one of the most appreciated and valued textile fibers. Silk filaments are secreted by the larvae of several types of silk moths to make their cocoons. Most silk is derived, however, from the larvae of the Bombyx mori moth, which has been widely cultivated in China for over 5000 years. Fragments of silk fabric dated to the late fourth millennium b.c.e. were found at Qianshanyang, in the province of Zhejiang, in China. There are, however, even earlier indications of the use of silk silk remains were found together with an eleventh-century b.c.e. mummy in Egypt, probably also providing evidence of ancient trading routes between the Far and Middle East. 

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). 

Iizuka, E. (1965). Degree of crystallinity and modulus relationships of silk thread from cocoons of Bombyx Mori and other moths. Biorheology 3, 1-8. 

Fig. 2.6 Structures of the pheromone binding protein (form A) from the silk moth Bombyx mori [96] obtained in six iterative cycles of combined...

Silk is produced from the spun threads from silkworms (the larvae of the moth Bombyx mori and related species). The main protein in silk, fibroin, consists of antiparallel pleated sheet structures arranged one on top of the other in numerous layers (1). Since the amino acid side chains in pleated sheets point either straight up or straight down (see p. 68), only compact side chains fit between the layers. In fact, more than 80% of fibroin consists of glycine, alanine, and serine, the three amino acids with the shortest side chains. A typical repetitive amino acid sequence is (Gly-Ala-Gly-Ala-Gly-Ser). The individual pleated sheet layers in fibroin are found to lie alternately 0.35 nm and 0.57 nm apart. In the first case, only glycine residues (R = H) are opposed to one another. The slightly greater distance of 0.57 nm results from repulsion forces between the side chains of alanine and serine residues (2). 

Pheromones, especially insect pheromones, have become common news stories in the popular press and hence are well known to most people. For instance, most elementary schools in the USA now include coverage of pheromones in general science and biology courses. Concomitant with this widespread coverage and inclusion in elementary school curricula is ongoing basic and applied research, which leads to important practical uses and beneficial applications. Since Butenandt s initial report on the pheromone of the silk worm moth, there have been many reviews of pheromones and recent ones are cited here. This review of the chemistry of insect pheromones will cover the isolation and identification of new pheromones and the synthesis of these compounds as well as other recently reported syntheses of important pheromones. 

Nature has long used reactions such as these to produce interesting solids such as cotton (seed pod), hemp (grass), and silk (cocoons for worms while they develop into moths) as fibers that we can strand into rope or weave into cloth. Chemists discovered in the early twentieth century that cellulose could be hydrolyzed with acetic acid to form cellulose acetate and then repolymerized into Rayon, which has properties similar to cotton. They then searched for manmade monomers with which to tailor properties as replacements for rope and sdk. In the 1930s chemists at DuPont and at ICl found that polyamides and polyesters had properties that could replace each of these. [Linear polyolefins do not seem to form in nature as do condensation polymers. This is probably because the organometaUic catalysts are extremely sensitive to traces of H2O, CO, and other contaminants. This is an example where we can create materials in the laboratory that are not found in nature.]... 

Tuskes, PM., Tuttle, J.P. and Collins, M.M. (1996). The Wild Silk Moths of North America. Ithaca, NY Cornell University Press. 

JUNVENILE HORMONES. One of several hormones, that retard the development of insects in the larval stage. So called because they prevent the insect from maturing by maintaining its juvenile characteristics. Obtained naturally from silk moths various syntheses indicate possible use as insecticides, especially for fire ants. Composition of one type is C18H30O3. 

A number of compounds important to animal physiology have been identified as isoprenoid compounds. Notable examples are vitamin A, retinal (Section 28-7), and squalene (Table 30-1). Also, terpene hydrocarbons and oxygenated terpenes have been isolated from insects and, like famesol, show hormonal and pheromonal activity. As one example, the juvenile hormone isolated from Cecropia silk moths has the structure shown in 3 ... 

Kent K. S., Harrow I. D., Quartararo P. and Hildebrand J. G. (1986) An accessory olfactory pathway in Lepidoptera the labial pit organ and its central projections in Manduca sexta and certain other sphinx moths and silk moths. Cell Tissue Res. 245, 237-245. 

The first identified insect OBP was the pheromone binding protein (PBP) of the silk moth A. polyphemus (Vogt and Riddiford, 1981). This 14 kDa protein appeared to be specific to the male antenna, was perhaps the most abundant soluble protein in the antenna, was located in the aqueous extracellular fluid that bathed the pheromone sensitive neurons, and could bind sex pheromone. The concentration of ApolPBP within the sensillum fluid was estimated to be about... 

Baker T. C. and Vogt R. G. (1988) Measured behavioral latency in response to sex-pheromone loss in the large silk moth Antheraea polyphemus. J. Exp. Biol. 137, 29-... 

Rogers M. E., Sun M., Lerner M. R. and Vogt R. G. (1997) SNMP-1, a novel membrane protein of olfactory neurons of the silk moth Antheraea polyphemus with homology to the CD36 family of membrane proteins. J. Biol. Chem. 272, 14792-14799. 

Steinbrecht R. A., Laue M. and Ziegelberger G. (1995) Immunolocalization of pheromonebinding protein and general odorant-binding protein in olfactory sensilla of the silk moths Antheraea and Bombyx. Cell Tissue Res. 282, 203-217. 

Vogt R. G. and Riddiford L. M. (1986b) Scale esterase a pheromone degrading enzyme from the wing scales of the silk moth Antheraea polyphemus. J. Chem. Ecol. 12, 469-482. 

Pheromones are powerful modulators of insect behavior. Since the isolation and identification of the first pheromone, (10E, 12Z)-hexadec-10,12-dien-l-ol, the sex attractant of the silk moth Bombyx mori, thousands of other insect pheromones have been identified. Our understanding of the sensory apparatus required for pheromone detection has also increased significantly. Coincidentally, B. mori was instrumental in many of these advances (see below). Volatile pheromones are detected by a specialized olfactory system localized on the antennae. The precise recognition of species-specific nuances in the structure and composition of pheromone components is essential for effective pheromone-based communication. The pheromone olfactory system of species studied so far exhibits remarkable selectivity towards the species-specific pheromone blend. Pheromones are emitted in low (fg-pg) quantities and are dispersed and greatly diluted in air plumes. Thus, pheromone olfaction systems are among the most sensitive chemosensory systems known. (Schneider et al., 1968). This chapter summarizes efforts (particularly over the past 10 years) to understand the molecular basis for the remarkable selectivity and sensitivity of the pheromone olfactory system in insects. The chapter will also outline efforts to design compounds that interfere with one or more of the early events in olfaction. 

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