Page last updated at 22:01 GMT, Tuesday, 11 November 2008
'Super-microscope' opens at Isis

By James Morgan
Science reporter, BBC News

Golden orb weaving spider, Oxford Silk Group 2008
The golden orb weaving spider spins one of the toughest fibres known

Their silk is stronger than steel and more elastic than nylon.

So how do spiders weave their miracle material?

Unravelling the recipe for gossamer could help us make clothes fit for Superman.

Whether you are designing flexible body armour, or biomedical implants, silk would be the ideal fabric.

But despite years of research, the world's scientists have yet to get anywhere near the gold standard - the dragline silk of an orb-weaving spider.

Five times tougher than steel. Three times more elastic than Kevlar. It is potentially bulletproof. But you can't make it in factories.

The sole manufacturer is a beastie the size of the end of your thumb.

Liquid assets

But if there is one thing we have learned from spiders (with the help of Robert the Bruce) it is this: "If at first you don't succeed, try, try again."

Spiders can weave seven different types of silk.

That is why the Oxford Silk Group are confident the new target station at Isis will help them crack the elusive formula.

The last thing you'd expect to find at the sharp end of a 200m neutron beam is cobwebs.

But Isis is full of surprises.

The new target station is specifically designed to "photograph" proteins and bio-polymers.

Arachnids produce around seven different types of silk - each with different protein structures and mechanical properties, optimised for different tasks.

They weave their threads from a liquid known as "dope", stored as gel inside the spinning glands.

The gel is a mixture of water-soluble proteins, which behave under flow like molten polymers.

When this solution is pulled through the spider's spinning glands, it turns into a solid fibre.

Dream weavers

The Oxford scientists know the ingredients of the dope. They know the balance of these molecules. And they even know the structure of the spinning glands.

"So why can't we create a fibre as good as the spider?" says Dr Chris Holland, a research fellow in the lab.

Oxford Silk Group
The Oxford Silk Group will use Isis 2 to unravel spider silk recipes

Dr Holland is investigating the conditions required for this liquid-to-solid transition.

Isis allows him to measure the molecules in their natural liquid state, whilst subjecting them to the same kind of flow that occurs during natural spinning.

"We are studying the environment the spider creates in order to spin a fibre," he explains.

"If we have a solution of silk proteins in water, we can ask - what shape are they in, and how do they change under flow?

"How does silk aggregate? That's the key thing."

Common thread

To find out, the team took a few drops of dope, and placed it in the line of the neutron beam at Isis 1.

Silkworms and spiders use liquids with similar flow properties to spin their silk

They measured the properties of the dope with a detector called LOQ - a small angle neutron scattering instrument - in combination with a rheometer.

Rather than studying the spider dope directly, they are using silkworm dope as a substitute.

"The liquids have essentially the same flow properties," said Dr Holland.

"Materially, the silkworm silk is very different, but the proteins flow in the same way - and also like molten polymers, with water as the solvent.

"That's good because it means we have more silk available to study."

Whereas spiders will attack, or even eat each other, silkworms are simple to rear, thanks to centuries of human cultivation.

In just a few days, a single silkworm spins up to a kilometre of silk thread.

"Silkworms are the cattle of the insect world. All they want is some mulberry leaves and some peace and quiet," says Dr Holland.

Flow diagram

The Oxford team have been working with Dr Ann Terry, one of the dedicated instrument scientists at Isis 1.

Dr Terry specialises in applying neutron scattering towards understanding the flow and crystallisation of polymers.

How neutrons are made at the new 200m Isis target station

"We have been eagerly awaiting Isis 2, because it is targeted at biosciences," she explains.

"First of all, it will have a higher flux of neutrons - around 20 to 40 times brighter.

"And the detectors are better positioned for studying biological materials."

All in all, it is the perfect machine for deconstructing the spiders' magic tricks.

"In the past, we never knew if the problem was what we were spinning with, or the way in which we were spinning it," says Terry.

"Target station 1 tells us we are heading in the right direction. Target station 2 will make us sure."

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