Spider Silk


Spider silk is a protein fiber spun by spiders. Spiders use their silk to make webs or other structures, which function as nets to catch other animals, or as nests or cocoons for protection for their offspring. They can also suspend themselves using their silk.

Spider silk is a remarkably strong material. Its tensile strength is comparable to that of high-grade steel, and about half as strong as Kevlar, but Spider silk is about a fifth of the density of steel; a strand long enough to circle the Earth would weigh less than 500 grams (18 oz).

Many small spiders use silk threads for ballooning, the popular, though technically inaccurate, scientific term for the dynamic kiting spiderlings use for dispersal. They extrude several threads into the air and let themselves become carried away with upward winds. Although most rides will end a few yards later, it seems to be a common way for spiders to invade islands. Many sailors have reported that spiders have been caught in their ship’s sails, even when far from land. The extremely fine silk used by spiders for ballooning is known as gossamer.

Many species of spider have different glands to produce silk with different properties for different purposes, including housing, web construction, defense, capturing and detaining prey, egg protection, and mobility (gossamer for ballooning, strands to let the spider drop down on as they are extruded). Different specialized silks have evolved with properties suitable for different uses. For example, Argiope argentata has five different types of silk, each used for a different purpose.

Peasants in the southern Carpathian Mountains used to cut up tubes built by Atypus and cover wounds with the inner lining. It reportedly facilitated healing, and even connected with the skin. This is believed to be due to antiseptic properties of spider silk. At one time, it was common to use spider silk as a thread for crosshairs in optical instruments such as telescopes, microscopes, and telescopic rifle sights.

Unlike herbivorous silkworms, spiders are cannibalistic and cannot be farmed. Due to the difficulties in extracting and processing substantial amounts of spider silk, there is currently only one known piece of cloth made of spider silk, an 11-by-4-foot (3.4 by 1.2 m) textile with a golden tint made in Madagascar in 2009. 82 people worked for four years to collect over one million golden orb spiders and extract silk from them.

One approach which does not involve farming spiders is to extract the spider silk gene and use other organisms to produce the spider silk. In 2000 Canadian biotechnology company Nexia successfully produced spider silk protein in transgenic goats which carried the gene for it; the milk produced by the goats contained significant quantities of the protein, 1–2 grams of silk proteins per liter of milk. They are attempting to spin the protein into a fiber similar to natural spider silk resulted in fibers.

The company Kraig Biocraft Laboratories has used research from the Universities of Wyoming and Notre Dame in a collaborative effort to create a silkworm that is genetically altered to produce spider silk.The Korea Advanced Institute of Science & Technology (KAIST) have succeeded in making spider silk directly with the bacteria E.coli, modified with certain genes of the spider Nephila clavipes.

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