Figure 7.

Hypothesized structure of the glue. Slug glue contains a network of proteins and a separate network of polysaccharides [3]. The proteins (black) are hypothesized to form a highly cross-linked network of sacrificial bonds, while the polysaccharides (red) are hypothesized to form a highly extensible second network. The polysaccharides carry a strong negative charge, and may associate with ions such as calcium and magnesium, which are loosely bound to ligands in the glue and may contribute by electrostatic interactions that allow the polysaccharides to fold up. (Online version in colour.)