Last updated May 24, 2018 at 12:39 pm
Glycoproteins hold the key in wet conditions.
Photo: iStock, PeteMuller
We’ve known for a while that spiders use a glue-type material to hunt and capture their prey, and that it works even in humid or wet habitats, but we haven’t known how or why. Until now.
Researchers from the University of Akron in the US have discovered that glycoproteins (proteins which consist of amino acids and sugar molecules) are the main component of spider aggregate glue, and can change their structure in wet conditions.
By doing so, these proteins fold in a way that makes adhesion favourable in the presence of water.
Ali Dhinojwala and colleagues hope their finding will inspire humans to develop new adhesion systems that can be used in such environments.
In their project they investigated how aggregate glue sticks on a sapphire surface, to determine the adhesion mechanism under wet conditions. Using sum frequency generation spectroscopy, they revealed the role played by glycoproteins.
They also found that small molecules, which are able to attract water, are ubiquitous in spider aggregate glue. These compounds sequester free water that normally covers the substrate and glue interface and thus impede adhesion.
“We demonstrate that glycoproteins act as primary binding agents at the interface,” they write in a paper published in Nature Communications. “As humidity increases, we observe reversible changes in the interfacial secondary structure of glycoproteins.
“Surprisingly, we do not observe liquid-like water at the interface, even though liquid-like water increases inside the bulk with increasing humidity. We hypothesize that the hygroscopic compounds in aggregate glue sequester interfacial water. Using hygroscopic compounds to sequester interfacial water provides a novel design principle for developing water-resistant synthetic adhesives.”
