Hygroscopic compounds in spider aggregate glue remove interfacial water to maintain adhesion in humid conditions

Abstract

Adhesion in humid environments is fundamentally challenging because of the presence of interfacial bound water. Spiders often hunt in wet habitats and overcome this challenge using sticky aggregate glue droplets whose adhesion is resistant to interfacial failure under humid conditions. The mechanism by which spider aggregate glue avoids interfacial failure in humid environments is still unknown. Here, we investigate the mechanism of aggregate glue adhesion by using interface-sensitive spectroscopy in conjunction with infrared spectroscopy. We demonstrate that glycoproteins act as primary binding agents at the interface. 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.

Towards Spider Glue: Long-read scaffolding for extreme length and repetitious silk family genes AgSp1 and AgSp2 with insights into functional adaptation

“…Glycosylations are responsible for the adhesive qualities of spider glue (Singla et al, 2018), and at least 80% of threonine residues in Argiope glues are likely O-glycosylated with mainly N-acetylgalactosamine (GalNAc) (Dreesbach et al, 1983;Tillinghast et al, 1993). The threonine residues are also flanked by glycine and proline, which is consistent with studies that show there is an increase in these residues around O-linked glycosylated threonines (Christlet and Veluraja, 2001;Yoshida et al, 1997).…”

“…Spider glue droplets exhibit 1) adhesion, typically to insect prey, 2) extensibility, to remain in contact with struggling prey, and 3) elasticity, to retain prey after extension. Glycosylations have been attributed to glue adhesion (Singla et al, 2018), however potential mechanisms for extensibility and elasticity have only been described for other silks. Orb web weaver glue droplets are more extensible (i.e.…”

Tough Adhesion of Nucleobase‐Tackifed Gels in Diverse Solvents

“…[10] Gao et al demonstrated a photodetachable adhesion principle to achieve strong adhesion and easy on-demand detachment for various materials. [29,30] As shown in Figure 1b, the gels presented a robust tensile strength of 47 kPa and toughness of 300 kJ m −3 at the high stain of 1520%. [17][18][19] However, most works only focused on the adhesion behavior in air and/or water, the technology of strong adhesion and acrylate adenine were utilized to fabricate adhesive gels via the radical polymerization in the mixed solvents of water and DMSO.…”

“…2019,29, 1900450 Diethyl ether (AR, 96%) and other organic solvents were purchased from Tianjin Tiantai Chemical Works Company.…”

Linking properties of an orb‐weaving spider's capture thread glycoprotein adhesive and flagelliform fiber components to prey retention time

“…The LMMCs serve several important functions. Along with glycoproteins, they confer hygroscopicity, causing the droplets' size and performance to change over the course of a day as they track environmental humidity (Figure d; Jain et al, ; Opell, Clouse, & Andrews, ; Opell, Jain, et al, ), they maintain glycoprotein structure and solvate glycoprotein, enhancing its surface interaction (Sahni et al, ), and they remove interfacial water from a droplet's contact footprint, enhancing adhesion (Singla, Amarpuri, Dhopatkar, Blackledge, & Dhinojwala, ). Optimal adhesion of an araneoid glue droplet is achieved when the viscosity of the droplet's glycoprotein is low enough to spread on a surface to establish sufficient adhesive contact, but high enough to ensure that the glycoprotein will cohere as it extends, thereby transferring adhesive force to the thread's axial lines (Figure c; Amarpuri, Zhang, Blackledge, & Dhinojwala, ; Amarpuri, Zhang, et al, ).…”