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Scientist fiddles with spider silk

Filaments are bundled, processed and played on violin

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7:14pm, April 17, 2012
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A new kind of violin string creates sounds as soft as silk. And no wonder, since it’s made of spider silk.

The strong-yet-stretchy protein fibers, which already have shown promise in everything from sutures to bulletproof vests, vibrate well when bowed, Shigeyoshi Osaki of Japan’s Nara Medical University reports in the April 13 Physical Review Letters.

Dragline silk can be stronger than steel, pound for pound. Orb-weaving spiders dangle from a single thread of this kind of silk and edge their webs with it. Filaments woven together into a slender rope can hold up a man.

To craft violin strings, Osaki packed thousands of dragline strands into bundles. Then he twisted together the bundles and treated them with a gelatin solution. Individual fibers’ curved surfaces became flat-sided, allowing the fibers to stack together tightly.

“The most interesting aspect to this paper is the change in shape from round to polygonal when they wound the fibers,” says Randy Lewis, a molecular biologist who studies spider silk at Utah State University in Logan. No one has made polygonal spider silk before, he says.

A Stradivarius violin strung with the shapely silk sang with stronger overtones than it did with other strings made of traditional materials. Professional violinists compared the sound favorably to that produced by catgut or steel strings, Osaki reports.

Still, don’t expect to see the spider strings in your local orchestra any time soon. They don’t rebound as well from stretching as steel does, so they have trouble staying in tune.

Also, finding enough silk to make the strings wasn’t easy. Osaki harvests the combined secretions of nearly 300 captive Nephila maculata spiders for his experiments.

“Natural spider silk is a very scarce material, limiting its widespread use from both a quantity and financial standpoint,” says Nikola Kojic, a bioengineer at Tufts University in Boston.

Kojic and other researchers hope spider silk will one day be mass-produced. Mammal cells loaded with a spider gene can churn out silk, as can goats genetically engineered to make it in their milk. But none of these artificial silks can yet compare to the real thing, spider-spun.

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