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Spider silk

March 2, 2011

Why are spider silk fibers so incredibly strong? That's a question scientists have been trying to answer for years and now researchers have found new information about the architecture of that fascinating raw material.

A spider web
Scientists have long searched for the secrets of spiders' silkImage: Fotolia/Alexander Maier

Scientists from the Heidelberg Institute in Theoretical Studies believe they have learned the secrets of spider silk, with new understanding of its structure down to the atomic level, according to research published in the Biophysical Journal in February.

Spiders spin silk which they use in their webs and to suspend themselves. The substance is remarkably strong and stretchy, and scientists have been trying to find out more about its composition for years.

Now a team of researchers, including senior study author, Frauke Gräter, believe they have gained deeper insight into the nature of this fundamental mystery.

"Because silk fibers continue to outperform their artificial counterparts in terms of toughness, many studies have tried to understand the mechanical characteristics of these extraordinary natural fibers," Gräter said in a press release.

The study revealed new information about the molecular structure underlying the mechanical characteristics of spider silk fibers. "Silk fibers exhibit astonishing mechanical properties," Gräter said. "They have an ultimate strength comparable to steel, toughness greater than Kevlar and a density less than cotton or nylon."

Useful for textile production

Peter Jäger, head of arachnology at Senckenberg Research Institute in Frankfurt, said that findings that help understand the composition of spider silk can be used by the industry, because they can help improve the production of artificial silk fibers.

Silk scarves from Italy (Photo: Vanessa Johnston)
The findings could help improve artificial silk productionImage: DW

"There are plenty of examples where these findings could be applied," he told Deutsche Welle. "Just think of ultra-light parachutes or bullet-proof vests, not to mention the broad field of textiles in general."

Scientists have known for a while that spider silk fibers consist of two basic components; one soft and amorphous and the other strong and crystalline. Dr. Gräter's team wanted to develop a better understanding of the mechanical properties of spider silk fibers and tackled the problem starting with these basic building blocks.

It started at the level of the atoms that make up the amorphous and crystalline subunits and dissected the contributions of these building blocks. Through a process of in-depth simulations depicting the relationships of these fundamental ingredients of spider silk, the team learned valuable new information.

New structural model for silk

What they discovered was that the soft amorphous subunits are responsible for the elasticity of silk and also help with the distribution of stress. The crystalline subunits provide the silk with its toughness which is dependent on the way that these elements are distributed in the fiber.

Using their simulations, Gräter and her team tested a range of subunit formations.

"We determined that a serial arrangement of the crystalline and amorphous subunits in discs outperformed a random or parallel arrangement, suggesting a new structural model for silk," she said.

Unappreciated arachnology

In comparison to other fields of research, arachnology in general is being treated as an orphan, according to Peter Jäger from the Senckenberg Research Institute in Frankfurt. There are only a dozen full-time researchers working with spiders in Germany.

The marginalization of the field is due to a combination of factors, which include arachnaphobia enhanced by film productions painting a scary picture of spiders, Jäger said.

And so, the Heidelberg team's findings are important not least, he said, because "Germany as a location for research is being put center-stage again in terms of arachnology."

Author: Nina Haase
Editor: Stuart Tiffen