Capture silk

Zhou, H. J., and Zhang, Y. (2005). Hierarchical chain model of spider capture silk elasticity. Phys. Rev. Lett. 94 art. no.-028104. 

Another interesting silk composite, the sticky capture silks of Nephila and Araneus, are complex, albeit microscopic, mechanical windlass systems that make good use of the physics of biological micro-engineering (Fig. 8.3). In the windlass silk (which operates in the wet state) the elasticity is given by a combination of surface tension of the aqueous coat and recoil of the plasticised silk fibre [12-14] while adhesion is bestowed by a separate glycoprotein complex [12, 15]. 

The mechanical behaviour of radial and capture silks differs greatly. For example, the wet and soft sticky spiral of the Araneus diadematus garden spider absorbs energy by large extendibility circa 500%) of the wetted thread which develops substantial force only after 100-200% extension with... 

The functional and developmental details of the two so very different elastic recoil mechanisms of the two types of capture silk micro-machines are interesting and deserve deeper studies. However, at present we do not even understand the interaction of form and function in the much more typical spider silk fibre such as a dragline filament. Recent studies indicate that the toughness of spider dragline silk may depend on the complex hierarchical structure of the fibre [11] which in turn depends on a complex... 

Spider webs are impressive for their complex architecture that gives rise to specific functions and in particular for their high performance ultrafine fimc-tionalized fibers from which the webs are constructed [1]. Several different types of silk are being used in web construction, including a sticky capture silk or fluffy capture silk, depending on the type of spider. Silk obtained... 

Spider Silk. Spider silks function ki prey capture, reproduction, and as vibration receptors, safety lines, and dispersion tools. Spider silks are synthesized ki glands located ki the abdomen and spun through a series of orifices (spinnerets). The types and nature of the various silks are diverse and depend on the type of spider (2). Some general categories of silks and the glands responsible for thek production are Hsted in Table 1. 

Over the last 400 million years, spiders have become highly diverse in the production and use of silks [1], reviewed in Ref. [2], This diversity is made necessary by the central role silk plays in a spider s life, e.g. prey capture, construction of shelter and reproduction. 

Indeed, this very development is captured in a footnote of Capital (n.337). Marx offers a modern instance of the combination of different handicrafts under the control of a single capitalist. He cites Blanqui on the silk-spinning and weaving industries of Lyons and Nimes, where women and children had once been... 

Purse-web spiders (Atypidae) capture their prey through the walls of a silk tube, thus hiding from the environment. Males stopped wandering around on sites from which female silk tubes had been removed (Coyle and Shear, 1981), suggesting a contact sex pheromone. However, the response could have been evoked by remnants of the silk tube. In the Hexathelidae, male Atrax infensus were attracted by volatiles from females, and this behavior was exploited to trap males, using traps with hidden females (Hickman, 1964). 

A spider s orb-web is formed by extrusion of a concentrated protein solution and stretching of the resulting fiber. The cross-strands, which are stronger than steel, resemble silkworm silk. The molecules contain microcrystalline p sheet domains that are rich in Gly-Ala repeats as well as polyalanine segments. The capture spiral is formed from much more elastic molecules that contain many -tum-forming sequences. These assume a springlike p spiral. See Box 2-B. 

Framed in the doorway was the portrait from the museum come to life. The Russian princess had stepped out of her canvas, in her shimmering blue silks, bringing with her more radiance and vitality than any Grand Master could have hoped to capture. Everything Trix had felt about that portrait, even in the photos, was standing in front of her, magnified a hundredfold by the woman s physical presence. 

The trapdoor spider cannot spin a web, it must use a different kind of devious strategy in order to capture its desired prey. (2) Instead of spinning a home, it uses its long legs to dig a tunnel in the ground. (3) It s about 11 inches deep. (4) Most of the time, it s two inches wide. (5) It lines the walls with silk, and then, using a combination of silk and dirt, it creates a tricky trapdoor to cover the top. (6) The lid keeps out heat, rain, cold, and predators, plus it fools potential prey. 

A more recent example of the rise and decline of an important product is rayon. As the first mass-produced synthetic fiber, it had phenomenal growth between World War I and II, capturing a large share of the cotton and silk markets. Competition from nylon and polyesters as well as improved cotton products, caused rayon s popularity to wane, resulting in a very small share of the total fiber market. Cellophane is another product that lost its market share—in this case to polyvinyl chloride, polyethylene, and polypropylene wrapping films. 

Most artificial protein polymers expressed to date have been inspired by sequences found in natural proteins. Structural proteins such as elastin, collagen, and silk exhibit usefid material properties and many researchers have attempted to capture these properties in well-defined engineered protein polymers. There is a wealth of knowledge related to these systems that will be discussed in depth in individual chapters of this volume. We will highlight only seleaed aspects of these protein polymers here. 

Silk is an interesting biomateiial that has been used since ancient times. It is a protein polymer (consisting of various amino acids) that is spun into fibers by insects like the silkworm, spider, scorpion, mites, and flies. Depending on the source and the arrangement of amino acids, there are a variety of silks, each having specific properties. Some evolutionary advanced species of insects are capable of spinning as many as nine or more varieties of silk for different purposes such as cocoon construction, lines for prey capture, safety lines or draglines, web construction, and adhesion [29]. The most widely characterized silks include those from the domesticated silkworm (Bombyx mori) and from spiders (Nephila clav-ipes and Araneus diadematus). 

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