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New spin on spider silk

R. Sundaram

MAHATMA Gandhi made goat's milk famous in a land of holy cows. He took it daily, as an alternative to cow's milk, compelled as he was by a bout of dysentery in 1918, though he had vowed to abjure animal products. Little would he have imagined then that g oat's milk at the turn of the century would claim credit for becoming the raw material for medical sutures and fishing lines. Yet, that is the new spin the bio-engineers are putting on goat's milk: Spider silk, whose elasticity and strength have been hel d in awe by scientists for centuries, will be now made from goat's milk.

The cobweb spinning spider, of course, had already become legendary by inspiring the oft-defeated Robert the Bruce, the Scottish king by showing him how to succeed. His exclamation ``If at first you do not succeed, try, try again!'' remains with us still , as also the spider's ability to spin webs. Only, the latter precedes Robert Bruce by at least 100 million years.

It has been estimated by scientists that spider silk is at least five times as strong as steel, twice as elastic as nylon, waterproof and stretchable. It is stronger than Kevlar -- used in bullet-proof vests which our Z category VIPs flaunt. Genetic stud ies affirm that the basic silk recipe dates back to the earliest orb weavers -- a class of cobweb spinning spiders that evolved 100 million years ago, and suggest that it leaves very little to be improved upon.

Without hot temperatures, high pressure or harsh chemicals, spiders are able to produce a steady stream of silk, one of the toughest fibres known. ``It is eco-friendly and a super fibre,'' said Dr David P. Knight of the Oxford University in England who, along with Dr Fritz Vollarath of the University of Aarhus, Denmark, describe the spider silk in a recent issue of

Nature.

In the case of silk spider, large scale forming is ruled out as they do not like living near each other. Also, it appears silk proteins are complex molecules and are difficult to decode. According to researchers, the secret lies in the spinning rather th an what is spun. Within the silk gland, the silk proteins are dissolved in a highly concentrated solution that is half water and half proteins.

From the silk gland the protein is squeezed out of a duct. The proteins fold up in rod shapes and are pulled out of the duct by knobby appendages known as spinnerets and they unwind, lock together and solidify into silk fibre.

Recently, Nexia Bio Technologies in Quebec successfully genetically engineered goat's milk to produce spider silk. The company spliced silk, making genomes of its goats configured so that the genes would act on only the mammary glands of lactating female goats.

The silk proteins are purified out of the milk into a whitish viscous liquid and then spun into fibres. These fibres can then be used for applications such as medical sutures and fishing line -- stronger than nylon, but environment-friendly as it decompo ses over time. According to Dr Turner, president, Nexia Bio-Tech, it requires only 200 goats to meet the world demand.