The amino acid 3,4-dihydroxyphenylalanine (Dopa) is a principle component of the adhesive plaques of marine mussels. However, the susceptibility of Dopa to autoxidize to a non-adhesive quinone form at neutral-to-basic pH conditions remains a major challenge to the implementation of Dopa in synthetic underwater adhesives. In this work, we used a surface forces apparatus to characterize the adhesive properties of a series of short, synthetic peptides (36 amino acids in length) that are inspired by a Dopa- and lysine-rich segment from the sequence of a key mussel foot adhesive protein, mfp-5. By comparing the Dopa, tyrosine, phenylalanine, and leucine (hydrophobic control) analogues of the same model peptide sequence, we show that the interfacial cohesion of these nanoscale peptide films depends critically on cation-π interactions when confined between two mica surfaces. Notably, the cohesive strength increases with increasing π-electron density of the aromatic groups, <i>F</i><sub>ad</sub>: leucine &lt;&lt; Dopa ~ tyrosine &lt;&lt; phenylalanine. Thus, while Dopa remains an important functional group for applications involving specific coordination chemistry, the incorporation of redox resistant aromatic residues in lysine-rich peptides may provide an attractive general platform for designing robust underwater adhesives that resist autoxidation over a wide range of aqueous conditions.

Engineering underwater adhesives: Leveraging cation-π interactions to govern peptide cohesion

249th National Meeting (2015)

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