Formation of S- and Z-twist supramolecular micro-ropes by peptide stereoisomers

Abstract

Abstract The intertwined strand arrangement in ropes, from micro- to macro-scale, results in tensile moduli significantly higher than those of single strands. Micro-scale ropes are found in biological systems, most commonly in mechanically-rigid collagen tri-strand arrangements. While human-made macro-ropes possess either left-handed (S) or right-handed (Z) twist, collagen exclusively adopts Z-twist architectures. Despite its natural abundance, the reconstruction and control of these supramolecular ropes in biomimetic systems using minimalist building units remains a fundamental challenge. Here, we demonstrate that cyclo-tryptophan-proline dipeptide stereoisomers self-assemble into complex crystalline supramolecular triple-helical structures. These unique architectures display tunable S- or Z-micro-rope-like twists governed by the configuration of tryptophan residues, as confirmed by co-assembly experiments and molecular dynamics simulations. Tensile testing revealed that these supramolecular micro-ropes exhibit significant moduli. These findings provide a potential platform for designing biomimetic functional helical materials with tunable supramolecular chirality and mechanical strength using minimalist building blocks.