Spider dragline silk is stronger than steel and tougher than Kevlar:
This type of silk is created inside a spider’s silk gland, where the proteins are kept in a dense liquid form called “silk dope.” As the spider spins its web, this liquid is transformed into solid fibers.
Although researchers have known that the proteins first gather into liquid-like droplets before turning into fibers, the precise molecular steps that connect this phase change to the final structure of the silk have remained a mystery until now.
The interdisciplinary team of chemists, biophysicists, and engineers used a combination of advanced computational and experimental tools — including molecular dynamics simulations, AlphaFold3 structural modeling, and nuclear magnetic resonance spectroscopy — to demonstrate that the amino acids arginine and tyrosine interact to trigger the initial clustering of the proteins.
Crucially, these same interactions persist as the silk fiber forms, helping to create the complex nanostructure responsible for its exceptional mechanical performance.
“This study provides an atomistic-level explanation of how disordered proteins assemble into highly ordered, high-performance structures,” added Lorenz.
Gregory Holland, SDSU professor of physical and analytical chemistry, who led the US side of the research, said one of the most surprising outcomes was how chemically sophisticated the process turned out to be.
“What surprised us was that silk — something we usually think of as a beautifully simple natural fiber — actually relies on a very sophisticated molecular trick,” Holland said. “The same kinds of interactions we discovered are used in neurotransmitter receptors and hormone signaling.”
He suggested the findings could therefore extend into human health research.
“The way silk proteins undergo phase separation and then form ?-sheet–rich structures mirrors mechanisms we see in neurodegenerative diseases such as Alzheimer’s,” Holland said. “Studying silk gives us a clean, evolutionarily-optimized system to understand how phase separation and ?-sheet formation can be controlled.”