Scientists nearer to synthetic spider silk
The promise of super strong medical sutures, bullet proof vests and biodegradable fishing lines made of spider silk may at last be realized.
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For decades, scientists have been trying to crack the secret of spider silk, which has a tensile strength that is far greater than steel’s per unit weight, is five times more elastic than Kevlar and is easily recyclable.
Years ago they found the genes for spider silk protein and even genetically altered goats to make the protein in their milk. But the results were disappointing because spider silk is spun in a particularly ingenious way, and from more than one protein.
Now Prof Andreas Bausch, Prof. Thomas Scheibel and Dr Sebastian Rammensee and colleagues at the Technical University Munich report in the Proceedings of the National Academy of Sciences how they have built a device that mimics the early stages in the assembly of spider silk, which may aid in the eventual synthesis of the strong, lightweight material.
Spider dragline silk consists of two proteins, ADF3 and ADF4, which coil into fibres in an irreversible process. After using bacteria to make the proteins, using standard genetic engineering methods, the researchers made an artificial spinneret, the organ used by the spider, to explore the ratio of proteins in various conditions.
“The major breakthrough is that this is the first time one has produced fully synthetic silk threads and understood why,” says Prof Bausch.
They suggest that three stages appear essential for fibre formation: that the proteins condense into spherical particles; that the acidity rises sharply; and that the particles be forced to slide past each other in a thin chamber.
The artificial fibres are grainy compared to natural spider silk fibres, but the researchers believe will be like the real thing when they copy the drying and drawing stages employed by spiders. In this way, says Prof Bausch, large scale spider silk production will become a reality “in the near future.”
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Dairy farmers don’t have to worry about suffering poisonous bites from the cows they milk.
Greta Binford, however, has slightly less cooperative subjects. Binford collects venom from the world’s most dangerous spiders.
Binford jokes she has “the dream job of most 8-year-old boys. I sit and watch spiders catch bugs.”
She specializes in the brown recluse spider and its 100 relatives. Currently, her lab at Lewis & Clark College houses 600 spiders collected in the U.S., Africa, Peru and elsewhere.
DNA analysis shows the spiders found in South America hold similarities to spiders found in Africa. By mapping patterns in DNA in spider venom, she hopes to learn more about why certain antidotes work against bites from some spiders but not others. “We’re trying to find out why that toxin is so different,” says Binford.
One current antidote that works for almost all spiders found in North America does not work on one particular brown spider from Peru, which happens to be found in basements in Los Angeles.
Binford is quick to point out that spider bites are rarely fatal. Particularly poisonous spiders leave behind hard to heal skin wounds.
To analyze venom, she must collect the poison.
That’s the tricky part.
She places a spider in a small chamber filled with carbon dioxide. Within a few minutes the spider falls asleep. That’s when she places the spider under a microscope on its back and proceeds to wash its fangs with individual drops of water, sucked away with a tiny, needle-sized vacuum.
That vacuum will come in handy in another way in a moment.
Then with a small electrical current she shocks the spider. It’s mild and does no damage. But at the moment of the shock, all of the spider’s muscles contract causing venom to come out its fangs, and, unfortunately, vomit out of its mouth.
“I have to work very hard to prevent the vomit from contaminating the venom,” Binford says, as she vacuums spider vomit with one tube and collects venom with another, all while peering through her microscope.
After a few seconds she’s done.
After another few minutes, the spider awakes and seems none the worse for wear.
She sees no lasting side effects on her spiders which she milks regularly over five or six years. “It doesn’t seem to shorten their life,” she says. “They go ahead, they eat. They mate, have babies.”
Binford and her colleagues hope to figure out “what cocktail of anti-venoms will work for bites from spiders from all of the Americas and maybe the world.”