Spider silk is one of the strongest and most complex fibers in the world, but also remains one of nature’s mysteries.
Lawrence Livermore National Laboratory (LLNL) researcher John Roehling and collaborators discovered that silk proteins inside spider glands are assembled in nanostructures and lend clues to how the silk is actually produced. The findings could be used to replicate the natural silk spinning process at bulk scale for use in biomedical materials, architectural design and civil and mechanical engineering. The research appears in the journal Proceedings of the National Academy of Sciences.
Many natural silks produced by spiders and insects are unique materials in their exceptional toughness and tensile strength, while being lightweight and biodegradable. The tensile strength of black widow spider silk, in particular, can rival steel wire of the same thickness and strength of Kevlar.
"By studying how spiders create their natural silks we hope to develop ways to synthetically replicate that process to create artificial silks of high quality," said Lucas Parent of Northwestern University and lead author of the paper.
There have been many attempts to create artificial silks using spider silk proteins, but they failed to achieve the advantageous properties of the natural material.
"When spiders produce their silks, all the action takes place within the spider’s silk gland and silk duct," Parent said. "The challenge is in developing and applying techniques that allow us to peer into silk glands of real spiders and observe the exceedingly small (sub-micron) structures therein and monitor their dynamics."
The team is interested in creating synthetic spider silks that are flexible, high-strength, high-toughness textiles to be used as protective armors and biomedical scaffolds. They also are interested in larger-diameter multi-fiber threads/ropes woven from artificial spider silks for architectural and engineering applications, as well as high-toughness ropes for tensile load-bearing.
The team used a combination of nuclear magnetic resonance spectroscopy and cryogenic transmission electron microscopy techniques to determine that the concentrated protein stores in the silk glands of black widows are complex, hierarchical nanoassemblies. Roehling specifically conducted the cryo-TEM tomography reconstruction and visualization for the project.
"We found that the physical form of the natural protein precursor nanostructures stored within spider glands undergo fundamental structural transformations during the initial stages of silk formation from shear forces," Roehling said.
In the study, the researchers investigated the dragline silk of black widow spiders because of its exceptional strength and toughness.
"Knowledge of this nanostructured protein is critical to the basic understanding of spider silk spinning, eventually allowing us to mimic this natural process using synthetic materials," Roehling said.
Other collaborators include researchers from Northwestern University, San Diego State University and Arizona State University.
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