The Components of Spider Aggregate Glue
Aggregate glue droplets have two distinct regions. The first is a glycoprotein core, the sticky part, which acts as an adhesive. The other is the outside aqueous solution. This connection of Low Molecular Mass Components great a dry environment, pulling in water. This concoction includes salts, small proteins, and even lipids (fats).
Biochemistry and Bioadhesives
The spreading behavior of Cyrtarachne glue droplets on moth scales shows acceleration and hyper-spreading relative to tests conducted on glass. We seek to determine the forces which govern this interaction in order to better understand the interaction between the material properties of aggregate glue and the topology of the moth wing. This work has applications towards synthetic adhesives aimed at adhering to contaminated or 'dirty' surfaces.
When compared to the glue droplets shown below, traditional orb-weaing spiders glue appears very different.
In these spread glue droplets, you can see only glycoprotein core and the spread aqueous solution
This spread glue droplet is however homogenous, with protein and salt everywhere. Shown by the protein stain above, where the glue droplet is entirely red.
Spread Cyrtarachne glue droplets show 'tendrils'. We believe this is caused by the separation of the proteins from salts as they spread.
When viewed, with a microscope, we can see there are crystals that form, perhaps concentration salts.
When stained, Cyrtarachen glue droplets show separate regions, with proteins only appearing in the center and at the droplet edges, shown by dark grey.
Our research into the chemical properties of this glue is only just beginning. Preliminary readings from Nuclear magnetic resonance spectroscopy (NMR) shown novel Low molecular mass components not yet found in other spider silks. We hope to identify some of these new components in the near furture.
Aggregate glue droplets absorb water from the air around them, getting larger in higher humidity. For most orb-weavers this process is reversible! For our study species Cyrtarachne, it isn't! The glue shrinks irreversibly and dries in low humidity. We believe this loss of resilience is caused by a change in the chemical structure of Cyrtarachne glue.
Future Directions
Our future research will devel further into the components and chemical behavior of Cyrtarachne glue in hopes of understanding the evolutionary changes that allow Cyratarachne to catch prey that other spiders often fail to. We hope to gain insight into the evolution of these glues and learn how to make better synthetic bioadhesives.
We are beginning our examination of the separation of glue components in spread Cyrtarachne glue droplets. Using Raman spectroscopy we are identifying protein and salts, and their relative distribution throughout. We hypothesize that these glue droplet components separate from one another, causing a micro drying event. We hypothesize this is a biologically relevant phenomonon, allowing Cyrtarachne glue to dry while spreading on moths surfaces.