Spider silk spinnerets

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. 

A) Experimental set-up for in situ X-ray diffraction during forced siiking. The spider is fixed by soft tape and mylar bandages to a metai support. The path of the thread from the spinnerets to the motorised reei is schematically indicated. Distance indications (to the spinneret exit) correspond to points where X-ray diffraction data were recorded. (B) Optical image of draw-down of N. edulis spider silk at a drawing speed of 20 mm s T (C) Diffraction pattern obtained at 23.5 +. 5°C. Miller s indices are indicated for selected reflections (for details see ref. 87). 

More viscous samples can be subjected to extensional flows when forced through slots or holes. Such flows are relevant to the spinning of polymer fibres, for example nylon threads or spider silk. In the latter case, the spider carries its own spinning machine, called a spinneret, to make its webs. 

The major textiles before the 1920s were wool (animal hair), cotton (a seed pod), and silk (a protein used for making cocoons). The silk spider also had a clever device in its abdomen for expelling a gel in a sac through a spinneret where reactions with air made a solid fiber with a uniform cross section. DuPont took this idea in spinning hydrolyzed cellulose into rayon fibers and scaling-the process up far beyond the needs of spiders. 

There are all sorts of silk that are found in nature. The stuff that is usually found in textiles comes from silkworms (Bombyx mori). They are not really worms, but the larvae of moths. They emerge from very small eggs with an incredible lust for mulberry leaves, which they consume until they are ready to. pupate and weave a cocoon around themselves. Unlike spiders, which spin silk from their rear end, silkworm silk is actually hardened saliva, which comes out of the mouth. The larva has a small spinneret on its lip, through which the silk emerges. The cocoon is formed from a single strand of silk that... 

Almost all spiders have only five segments in the abdomen, and these are generally fused with no external trace of segmentation, while primitive spiders had as many as twelve segments in their abdomen. The last two abdominal segments are specially modified into spinnerets which secrete the silk threads for which spiders have become well known. There are one to four pairs of spinnerets present, even on those spiders which do not spin webs. The silk has many other functions, such as in... 

For example, most of the tensile strength and stiffness data quoted for natural silks are inaccurate. Silks typically have a highly non-uniform cross-section, due to the nonconstant linear production rate of the fibre under natural spinning conditions, and the fact that spinneret orifice sizes can be changed continuously by the spider or larva unless the animal is anaesthetised. Here, non-uniform refers both to the cross-sectional shape, which does not have a simple outline, and to the fact that this shape and its enclosed area can vary with position along the fibre (Dunaway, 1994 Dunaway et al., 1995a ... 

The hierarchically built fiber is produced by the assembly of silk proteins through the spider s sophisticated spinning spinneret [9]. The silk assembly process occurs via a lamellar liquid crystalline assembly into nano fibrils to form the final silk thread (Figure 6.3). A diagrammatic optical section of the secretory part (A- and... 

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