Two Faces of Amine–Catechol Pair Synergy in Underwater Cation−π Interactions

Abstract

Cation−π interactions play important roles in various biological systems. Recently, cation−π interactions have been suggested to have considerable roles in mussel adhesion, which is the most well-known biological model for underwater adhesion. Although amine−catechol pair synergy in mussel adhesion has been well studied for surface adhesion in the aqueous phase, little is known about its effect on cohesion, particularly in intermolecular cation−π interactions. Here, we designed musselinspired model peptides to characterize the amine−catechol pair effect on cation−π interactions. We used nanomechanics to measure the interaction directly and probed cation−π interactions with nuclear magnetic resonance and Raman spectroscopy. Moreover, we established the origins of these effects through intensive Raman spectra analysis. We discovered that amine−catechol pairs have antisynergetic effects on intermolecular cation−π interactions, and this finding may provide the insight that the amine−catechol pair synergy may not always work on the positive side in underwater adhesion.

Hydrogels for underwater adhesion: adhesion mechanism, design strategies and applications

“…The strength of the cation-p interaction inside the hydrogel will affect its cohesion strength, and the strength of the cation-p interaction will be affected by the type of cation, the type of aromatic group, and the position of the aromatic group and the cationic group. For example, having cationic groups and aromatic groups in adjacent positions on the same polymer chain has an inverse synergistic effect on the cation-p interaction, 87 and the strength of the cation-p interaction will weaken with the hydroxylation of aromatic hydrocarbons. 88 However, the hydroxylation of aromatic hydrocarbons in polymer hydrogels can form more hydrogen bonds, so it is necessary to comprehensively consider the effect of different ratios of intermolecular forces on the adhesion properties of hydrogels.…”

Principles of Cation−π Interactions for Engineering Mussel-Inspired Functional Materials

“…Controlling the positioning of catechol and amine groups in a polymer chain is an effective method to modulate adhesive performance. − SCP adhesion assays of sequence-defined polymers demonstrated that the adhesion energy of a polymer with adjacent catechol and amine residues was significantly higher than that of polymers with an additional spacer between the catechol and amine groups (Figure d) . Moreover, terminal amides can displace the surface hydration layer on substrates and provide a synergistic effect with catechols for underwater adhesion, which is attributed to the ionic resonance structure of primary amides .…”

Probing and Manipulating Noncovalent Interactions in Functional Polymeric Systems

“…For example, for the Trp-rich mussel foot protein from Perna viridis (pvfp-1), the adhesion energy between the two symmetric films could be >2.3 mJ/m 2 , and for a Tyr-containing recombinant Mytilus foot protein (rmfp-1), the symmetric adhesion was measured to be 2.9 mJ/m 2 . In both cases, the adhesion strength decreased with the increase of K + concentration, demonstrating K + could effectively compete with the lysine−π interactions in the proteins. , Recently, the antisynergitic effect of amine-catechol pairs on underwater cation−π interactions was reported in a series of mussel-mimic model peptides . It was found that when the aromatic group (i.e., DOPA, Phe, Tyr) and the cationic lysine were separated by a linker of two glycine moieties, the cohesion of the protein films would be significantly enhanced compared to that of proteins with flanking lysine and aromatic residues.…”