(497f) Explaining Catechol-Cation Binding Synergy with Bond Energies and Lifetimes

Marine mussels use a protein glue to attach to a wide variety of substrates under water. This robust adhesion to contaminated substrates in high salt aqueous environments makes the mussel glue an attractive inspiration for synthetic adhesives. A major adhesive protein produced by mussels contains many paired catecholic 3,4-dihydroxyphenylalanine (Dopa) and cationic residues (Lys and His) residues which constitute about 30% of the total residues in the protein. Previous work has shown that molecules containing both catechols and cations adhere to inorganic surfaces with higher adhesion forces than molecules with either catechols or cations alone. To further study catechol-cation binding synergy, small molecules were synthesized with systematically varying intramolecular spacing between catechols and cations. Adhesion forces of monolayers of the molecules confined between mica surfaces were measured using a surface forces apparatus (SFA). Based on our results, we propose a new explanation for binding synergy between catechols and cations based on the relationship between solution conditions, bond lifetimes, and competitive binding of adhesive moieties to mica surfaces. An understanding of catechol-cation binding synergy should aid the design of biologically inspired adhesives for medical, dental, and marine applications.