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Wednesday, August 11, 2010

Engineering spider silk

Ounce for ounce, spider silk is stronger than steel and tougher than Kevlar. There would be a myriad uses in the medical and material sciences for threads that are thinner than human hairs yet stronger than steel. Yet, collecting natural spider silk can be problematic as spiders make uncooperative life stock. Sang Yup Lee at the Korea Advanced Institute of Science and Technology (KAIST) and his collaborators, Professor Young Hwan Park at Seoul National University and Professor David Kaplan at Tufts University recently managed to overcome this problem by bioengineering silk.

The scientists got Escherichia coli bacteria to produce the spider silk protein. This was a daunting task in and of itself. For one thing, spider silk protein is a behemoth at 285 kilodaltons. To put that in perspective, ovalbumin, the main component of egg whites, weighs in at only 45 kilodaltons. Silk is also highly repetitive in nature, requiring enormous quantities of only a few different amino acids. In short, spider silk is not something bacteria like to waste their resources producing. With a bit of metabolic engineering and a vast pool of the appropriate raw materials, Lee and his team were able to coax the bacteria into producing the desired silk protein.

The resultant silk protein could be spun into artificial fiber comparable to spider dragline silk. The scientists expect to be able to use similar methods to create other kinds of artificial silk or silk-like materials. After all, spiders are known to produce at least five different kinds of silk, depending on whether they wish to support their body weight, capture prey, protect their young, or perform a host of other actions. Each of these silks would find wide use in human activities.

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