Saturday, 26 May 2012

Spider silk has been known to man as one of the toughest material on earth. It is durable and stronger than steel. However, what makes it a desirable medium in material science is that it is not only strong, it is also flexible. An example is the golden silk spider.

Pic 1. Golden Silk Spider
 The spider produces a silky web. This web is basically a protein structure. The protein structure is secondary and a β pleated sheet. The sheet consists of many hydrogen bonds that work together to resist external forces and dissipate energy. Due to this, spider silk have the ability withstand tremendous amount of stress.
·         It has a tensile strength of 136 000kg per square inch.
·         It is lightweight and durable
·         It is biodegradable
·         It is STRONGER than STEEL

Pic 2. The protein structure of spider silk (β-pleated sheets and Hydrogen Bonds)

The hydrogen bonds present the proteins are 100 – 1000 times weaker than metallic bonds in steel. However, with so many hydrogen bonds present, they are able to resist and dissipate energy by working together. They are also very ductile and can stretch up to four times their original length and they can hold their strength in very extreme temperatures -40°C to 220°C.
Hence, spider silk could be incorporated in our everyday lives. It could effectively replace Kevlar as bullet proof vests, coat aeroplanes and cars, bringing about cheaper prosthetics. The applications are limitless.
However, there is one problem. Spider silk cannot be mass produced. Scientists have tried to breed spiders and farm their silk webs like silk worms. Spiders naturally cannibalise. Hence, the spiders that were bred kept eating one another and this way was neither productive nor economical.
Scientists at Nexia Biotechnologies have come up with a product called Bio Steel. This product is made from spider silk which is extracted in an ample amount from goat’s milk. This feat is achieved by adding the silk producing gene of the golden silk spider to the Nigerian dwarf goat’s chromosomes.
 Meet Webster and Peter:

Pic 3. Webster and Peter

They are Nigerian dwarf goats.  According to Nexia, the silk glands and milk glands are similar. Hence, they spliced the genes from both the spider and goat. As mentioned earlier, the now “cut” genes are quite similar as their ends are complimentary to each other. The genes are then recombined and incorporated back into the goat’s genome.  They were programmed to turn on only in lactating females, and through cloning, they have managed to breed goats that have the spider silk genes. Webster and Peter are the first. Hopefully, they will breed and the subsequent generations will carry the spider silk genes too.
Milk from the goats is collected and silk proteins will be isolated and purified. A whitish liquid will remain, which can then be spun into fibres for the many applications.
The applications for bio materials such as spider silk are far and wide. Hopefully, in a few years’ time, this technology will be perfected and available to everyone. 

Spider gene spins goat’s milk into super fibre 
Spider’s silk and goat’s milk 
Spinning Tough Spider Silk from Goat’s Milk 
Researchers unravel the secrets of spider silk strength
The golden silk spider
Reece, Campbell Biology, 8th ed. (Australian version), 2009 

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