Meeting Abstract

S7.5  Tuesday, Jan. 6  Multiple cross-linking mechanisms in molluscan adhesive gels SMITH, A. M.*; BLOOM, A.; GARCIA, S.; Ithaca College, NY; Ithaca College, NY; Ithaca College, NY asmith@ithaca.edu

Some terrestrial slugs produce remarkably sticky and elastic gels as defensive secretions. Previous work on these gels has shown that metals play a central role in their cross-linking. The transition metals iron and zinc are common in these gels, as are calcium and magnesium. A major question is how these metals cross-link the gel, and whether there is more than one mechanism by which they do so. Chelation of metals with EDTA for an extended time breaks down the mechanical integrity of the gel, thus demonstrating a direct effect of the metals on gel mechanics. Furthermore, metals, particularly calcium, were shown to have a general stiffening effect on commercial gels at the concentrations seen in the glue. Metal removal does not completely break down the gel, however, as size exclusion chromatography experiments show that the major cross-links involve a 40 kDa protein and these are unaffected by metal chelation after the glue sets. If chelation occurs before the glue sets, however, this cross-link does not form either. Measurements of the stiffness of commercial gels with metals and glue proteins added separately and together show that both stiffen gels on their own, but the effect is merely additive; they are not necessarily interdependent. The findings suggest that the mechanical strength of the gel depends in part on metals such as calcium and zinc forming direct cross-links and also on other cross-links involving the 40 kDa protein, which are catalyzed by metals before the glue sets.