Untangling the secret of spider webs' superpower
LOWELL, Mass. – In the "Spider-Man" movies, the superhero was able to stop a runaway train from crashing by using spider webs that he shot from his wrists.
While daring feats such as this were created using Hollywood special effects, there is a measure of scientific truth to the extraordinary toughness of the spider web's fiber, or silk, according to a UMass Lowell researcher.
"Spider silks are the toughest biological material," said Jessica Garb, an associate professor in UMass Lowell's Department of Biological Sciences. "They are tougher than steel, yet weigh much less, and some spider silks can be stretched up to three times their length without breaking."
Garb's study, funded by a four-year, $335,000 National Science Foundation (NSF) grant, is looking at what makes spider silks so tough and could lead to the development of a new generation of high-performance synthetic biomaterials for consumer, medical and military applications.
"Several startup companies are already producing products based on spider silk using genetic engineering techniques and our work will add to these endeavors by providing new recipes for even tougher silk-based materials," said Garb. "For example, these materials could be used to improve helmets and body armor or other protective equipment, medical devices like prosthetics, bandages and sutures, even sports gear."
Garb and a team of researchers including UMass Lowell students are examining the molecular composition, biomechanical properties and evolution of an exceptional type of silk produced by an arachnid species known as Darwin's bark spider. One of the silks spun by Darwin's bark spider, known as dragline silk, has been shown to be twice as tough as those produced by other known spider species and 10 times tougher than the Kevlar used in body armor, Garb said.
"This particular species is endemic to the rainforests of Madagascar and constructs the largest orb webs ever recorded, capable of extending across rivers and lakes," she said.
The goal of the project is to examine the molecular makeup of this dragline silk and compare it to those from other closely related species to understand what makes Darwin's dragline silk ultra-tough, how these unique properties have evolved and whether the extreme toughness of this silk is associated with the evolution of giant webs.
Dragline silk is one of seven silk types produced by orb-weaving spiders. It is used to construct the radial lines and frame lines of orb webs, and it is designed to absorb the kinetic energy of impacts from flying prey, according to Garb.
"Toughness is how much energy a material can absorb without breaking. Dragline silk is tough because it combines high tensile strength with elasticity," she explained.
Garb's lab at UMass Lowell will characterize the genes and proteins that make up dragline silk from Darwin's bark spider and some of its closest relatives.
"We will use tools from microscopy, molecular biology, high-throughput DNA sequencing, protein biochemistry, evolutionary biology and bioinformatics to determine what the proteins are, how they are related to each other evolutionarily and how the features of silk proteins dictate the fibers' mechanical properties. And by analyzing the genes that encode the proteins, we hope to understand how to replicate this material using genetic engineering for diverse textile applications," said Garb, who is working in partnership with the University of Akron and the University of Vermont.
Assisting Garb in her lab at UMass Lowell currently are Molly Dawson, a graduate student working on her master's degree in biological sciences, and Winny Rojas-Velez, an undergraduate biology major. Robert Haney, a postdoctoral researcher with Garb is the co-principal investigator on the project.
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