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Repellent slime has material virtues

Threads from hagfishes' defensive goo demonstrate superior strength and flexibility

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8:56pm, December 19, 2012
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Step aside spiders. Threads made by another creepy-crawly — the eel-like hagfish — may lead to superior new fibers for parachutes, packaging and perhaps even clothing. A new study that examines the mechanical properties of threads made from hagfishes’ slimy mucus finds the fibers are both strong and stretchy, and may serve as a model for creating superior new materials.

“The tensile properties approach those of spider silk, and that’s very exciting,” says biomaterials specialist Douglas Fudge of the University of Guelph in Canada. Synthetic fabrics such as nylon are derived from petroleum, notes Fudge, so studying hagfish threads may lead to renewable “green” materials for making all sorts of things.

To study the threads, Atsuko Negishi, a researcher in Fudge’s lab, collected buckets of slime from Atlantic hagfish (Myxine glutinosa). The long, slender jawless creatures have lines of slime pores that run down the sides of their body; some species have more than 100 such pores. When hagfish are provoked or stressed, the pores eject copious amounts of slime, which gets caught in the gills of predators — including sharks — making them gag and back off.

“There’s very little that’s been known about hagfish. People don’t like them and think they are gross,” says research scientist Vincent Zintzen of the National Museum of New Zealand in Wellington. “The idea of looking at their slime is very interesting. It’s totally different from anything that we’ve seen in the natural world.”

Negishi and her colleagues anesthetized their hagfish, dried them off and then stimulated them with electricity to prompt slime ejection. Then the researchers concentrated the slime’s proteins. They found they could produce threads up to 20 centimeters long by dripping the concentrated proteins onto the surface of a salty buffer solution. For reasons that aren’t clear, the threads then form a film that can be drawn out and spun into a fiber, Negishi, Fudge and their colleagues report in the Nov.12 Biomacromolecules.  

When the threads were stretched in water, they contorted into the same molecular shape that’s believed to give spider silk its strength and toughness. The researchers also discovered that hagfish threads are super stretchy, tripling in length before breaking.

The proteins that make up the threads belong to a class known as intermediate filaments that also includes keratin, the stuff of hair and fingernails. These proteins are also found in cells, where they provide structural support and play a role in resisting stress, among other things. Maybe the hagfish version of the proteins will have special properties, Fudge says, or they may end up being like a lot of intermediate filaments, which would also be intriguing. “We’re using it as a source of inspiration,” he says.

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