Short-Sequence Superadhesive Peptides with Topologically Enhanced Cation−π Interactions

In this study, using the surface force apparatus, we report engineered peptides with short sequences of phenylalanine (F) and lysine (K) amino acids capable of forming the most efficient cation−π interactions reported for underwater adhesive systems in the literature to date. This outstanding cation−π binding efficiency can be achieved between surfaces coated using these peptides when an isolated K amino acid is flanked by F amino acids in the peptide sequence. Surface force analysis and molecular dynamics (MD) simulation reveal that such a sequence of amino acids minimizes repulsive hydration forces that prevent effective cation−π interactions. The resulting peptides exhibit cation−π interactions that are 14 times more efficient than cation−π interactions between the homogenous films of F and K. In addition, the resulting adhesive energy of two surfaces covered with these peptides is more than twice larger than the best-performing underwater adhesive energy based on cation−π interactions. Such effects of molecular sequences on the binding efficiency of underwater adhesives suggest that a short sequence of amino acids, which is engineered to have effective cation−π interactions, can be sufficient to improve upon the adhesive performance of complex mixtures of macromolecules as underwater superadhesives. The results provided in this study allow to unambiguously rationalize the molecular determinants necessary for strong cation−π interactions and offer new guidelines for developing mussel-inspired underwater adhesive materials.