Revealing the Hidden Natural Ionic Liquids in Spider Glue: Insights from the Adhesion Process

The adhesive properties of aggregate glue droplets in spider orb webs are conferred by a complex composition of highly glycosylated and phosphorylated proteins, which dissolve in low molecular mass compounds. Although aggregate glue droplets exhibit heterogeneous structural distributions upon attachment to substrates, limited knowledge exists regarding alterations in the distribution of their chemical components before and after attachment. Understanding the spatial distribution of chemical components within these droplets before and after attachment is crucial to unraveling the underlying adhesion mechanisms. In this study, we employed in situ measurement methods to investigate the distribution of low molecular mass compounds and proteins within aggregate glue droplets from Neoscona nautica, thereby visualizing the role of specific low molecular mass compounds in facilitating glycoprotein modification within the aggregate glue. Our findings indicate that the constituents of aggregate glue droplets include at least one ionic liquid: hydrated choline dihydrogen phosphate, and the extent of glycoprotein modification within the aggregate glue is contingent upon the concentration of this ionic liquid.