Mystery of how black widow spiders create steel-strength silk webs

 

Black widow spiders and their relatives, native to temperate climates in North America, Europe, Asia, Australia, Africa, and South America, produce an array of silks with exceptional materials properties.

Scientists have long known the primary sequence of amino acids that make up some spider silk proteins and understood the structure of the fibers and webs. Previous research theorized that spider silk proteins await the spinning process as nano-size amphiphilic spherical micelles (clusters of water-soluble and non-soluble molecules) before being funneled through the spider's spinning apparatus to form silk fibers. However, when scientists attempted to replicate this process, they were unable to create synthetic materials with the strengths and properties of native spider silk fibers.

The research team was able to more closely see inside the protein gland where the silk fibers originate, revealing a much more complex, hierarchical protein assembly. Thus "modified micelles theory" concludes that spider silk proteins do not start out as simple spherical micelles, as previously thought, but instead as complex, compound micelles. This unique structure is potentially required to create the black widow spider's impressive fibers.

The black widow spider silks are spun from hierarchical nano-assemblies (200 to 500 nanometers in diameter) of proteins stored in the spider's abdomen, rather than from a random solution of individual proteins or from simple spherical particles. If duplicated, the practical applications for a material like this are essentially limitless and could include high-performance textiles for a military, first responders and athletes; building materials for cable bridges and other construction; environmentally friendly replacements for plastics; and biomedical applications.