Researchers, in collaboration with Northwestern and San Diego State, look at the process of spinning such incredibly strong silk at a molecular level

Scientists at Arizona State University are celebrating their recent success on the path to understanding what makes the fiber that spiders spin — weight for weight — at least five times as strong as steel.

One of the fundamental mysteries of spider silk that has limited scientists’ ability to produce artificial silks of the quality of natural silks has just been explained by researchers in ASU’s School of Molecular Sciences in collaboration with a team from San Diego State University and Northwestern University.

Their results, published online today in the Proceedings of the National Academy of Sciences (PNAS), are in a paper titled “Hierarchical spidroin micellar nanoparticles as the fundamental precursors of spider silks.”

"Spider silk has a unique combination of mechanical strength and elasticity that make it one of the toughest materials we know," said Jeff Yarger, professor in the School of Molecular Sciences in the College of Liberal Arts and Sciences.

Spider silk is an exceptional biological polymer, related to collagen (the stuff of skin and bones) but much more complex in its structure. The ASU team of chemists is studying its molecular structure in an effort to produce materials for uses ranging from civil and mechanical engineering to artificial, yet biocompatible, tendons.

“Everybody’s familiar with silk, because they’re familiar with silkworm silk. The silk trade has been around for a long time. But spider silk has a much larger variety in its properties,” Yarger explained.

Unfortunately, spiders don’t produce silk in large quantities. “You can put lots of silkworms in a small area and genetically modify them to go from the larval state to a moth in 20 to 30 days. Spiders take longer. But let’s get to the crux of it — spiders don’t like each other. They eat each other,” Yarger said. This, of course, eliminates the possibility of farming them en masse.

Scientists have come up with ingenious ways to get around this problem. They have genetically engineered silkworms, E. coli and even goats to produce spider silk. Unfortunately, while these organisms produce the same proteins that spiders make, they don’t have the same mechanical properties as the natural product. They aren’t as strong, for instance, or as flexible.

This is where the current research comes in — Yarger was joined by Dian Xu, Samrat Amin and Brian Cherry, all from ASU; Gregory Holland, associate professor of chemistry from San Diego State University; and Nathan Gianneschi, professor of chemistry from Northwestern University.