Tyrosine-mediated two-dimensional peptide assembly and its role as a bio-inspired catalytic scaffold.

In two-dimensional interfacial assemblies, there is an interplay between molecular ordering and interface geometry, which determines the final morphology and order of entire systems. Here we present the interfacial phenomenon of spontaneous facet formation in a water droplet driven by designed peptide assembly. The identified peptides can flatten the rounded top of a hemispherical droplet into a plane by forming a macroscopic two-dimensional crystal structure. Such ordering is driven by the folding geometry of the peptide, interactions of tyrosine and crosslinked stabilization by cysteine. We discover the key sequence motifs and folding structures and study their sequence-specific assembly. The well-ordered, densely packed, redox-active tyrosine units in the YYACAYY (H-Tyr-Tyr-Ala-Cys-Ala-Tyr-Tyr-OH) film can trigger or enhance chemical/electrochemical reactions, and can potentially serve as a platform to fabricate a molecularly tunable, self-repairable, flat peptide or hybrid film.