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News Clippings
New Scientist, 10 October 1998
Spinning steel
By Phil Cohen, San Francisco
By lacing goat's milk with synthesised spider
proteins, researchers in Quebec plan to make an
incredibly light fabric that is both biodegradable and
strong enough to stop bullets. Called biosteel, it could
become a green alternative to the high- strength plastics
used to package shampoos or make commercial fishing nets.
Jeff Turner, president of Nexia Biotechnologies, says the
biodegradable fabric would need to be sealed from the
environment if used in critical applications such as body
armour or spacecraft. This is because bacteria could get
in and digest it.
Turner's team has already taken the first step towards
creating biosteel by transferring the spider gene for the
protein into goat mammary cells and collecting soluble
protein from the milk. And they expect genetically
engineered goats to start producing the protein in the
next few months.
While nobody has yet made a fabric from biosteel, Turner
is convinced the protein can be turned into a
supermaterial because of its natural role in the silk of
a spider's web. "When you think of what a web has to
do, its extreme strength makes perfect sense," he
says. The silken threads of the web must be nearly
invisible to prey and yet be able to bring a fly to a
screeching halt.
Evolution came up with a two-pronged answer to this
problem. First came a rock-solid protein, capable of
making many bonds with its neighbours. Then, the spider
developed a unique way of spinning the protein into a
whisper-thin thread. As the spider secretes the protein
solution, the silk dries and pulls taut, transforming the
proteins into a nearly crystalline and completely
insoluble cable. This explains why webs don't dissolve in
the rain. Tests on natural silk show that it can be
stronger and more elastic than high-tensile steel or the
Kevlar found in body armour.
But the very properties that make silk proteins strong
also make them difficult to produce. When bacteria are
engineered to produce large quantities of the protein,
for example, it links up in chains into a disordered,
insoluble mess. Its ability to bond with its neighbours
can happen in a very ordered or a disordered
fashion--depending upon how the proteins fold as they
form. Which is why Turner and his colleagues decided to
mimic the spider's own method of production by using goat
mammary cells. It turns out that the way mammals produce
milk proteins and spiders make silk proteins are broadly
similar. Both are produced in skin-like epithelial cells,
then held in a space, or lumen, where shear stresses on
the protein are minimised.
So far so good. But Turner cautions that the work is
still in its early stages. It will take about a year
before the herd of biosteel goats is large enough for
Nexia's scientists to collect the protein they need to
start making fabric. Then they will face the next great
hurdle: how to match the spider's spinning skill.
"Nature probably took a long time to get this
process right," he says. "I suspect the same
will be true for us."
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