Beta strands in the silk proteins are essential to the formation and strength of the golden orb-web spider's threads. Photo by RIKEN
May 29 (UPI) -- A team of scientists has discovered a previously unidentified structural component key to the formation of spider silk and its extraordinary strength.
Prized for its strength and flexibility, material scientists have long tried to produce synthetic analogs for spider silk. The results of previous efforts, however, have been mixed.
Studies have shown the importance of beta sheets, or beta strands, the secondary structure in spider silk proteins, but scientists have struggled to understand how these strength-giving structures form.
The transformation from soluble proteins to crystalized silk happens fast, making it difficult to study the proteins' structures.
In order to gain new insights into the formation process, scientists at Japan's RIKEN Center for Sustainable Resource Science genetically modified bacteria to produce the silk proteins of a golden orb-web spider.
The scientists used advanced imaging techniques to analyze the repeating pattern found within the soluble proteins. Their analysis showed the secondary structures feature a combination of random coils and a pattern called polyproline type II helix.
It turns out the helix pattern is essential to super strong silk.
The polyproline type II helix lends structure to the soluble proteins and allows for the formation of beta sheets, which helps the proteins crystallize and quickly be woven into silk threads.
"We were fortunate to be able to use a combination of powerful methods, including solution-state nuclear magnetic resonance spectroscopy, far-UV circular dichroism spectroscopy, and vibrational circular dichroism spectroscopy, to analyze the protein before it formed into the beta-sheets," RIKEN researcher Nur Alia Oktaviani said in a news release. "It was very satisfying to discover this special conformation that leads to the formation of the beta-sheets."
Researchers detailed their breakthrough in the journal Nature Communications.
"Spider silk is a wonderful material, as it is extremely tough but does not contain harmful substances and is readily biodegradable, so it does not exert any harmful load on the environment," said lead researcher Keiji Numata. "We hope that this discovery will help make it possible to create artificial silk that will prove useful for society."