Hybrid pH Responsive Supramolecular Polymers Through the Combination of the Ureido-Pyrimidinone Motif with β-Sheet Peptide Sequences.

Supramolecular biomaterials based on 1D supramolecular polymers in water replicate the fibrous and dynamic structures of natural architectures. Peptides, valued for their biocompatibility, are commonly employed as building blocks for supramolecular biomaterials, often in combination with large aromatic or hydrogen-bonding groups at the N-terminus to improve their structural stability. Herein, the self-assembly properties of two β-sheet peptides combined with the ureido-pyrimidinone self-dimerizing motif in aqueous solution are investigated in detail. The assembly of the resulting molecules is demonstrated to be intimately dependent on the β-sheet sequence, while the incorporation of a hydrophobic spacer enhances the assembly of the monomers, irrespective of the peptide sequence employed. Furthermore, the assembly of each monomer is significantly enhanced at pH = 3.0 while being stable between pH = 5.0 and 9.0. Only at pH = 12, upon enolate formation, the transition to random coil conformation is observed for all the monomers. The supramolecular polymers developed hereby point to fundamental design principle toward the development of UPy-peptide based materials with tuneable properties and potential applications in the biomedical fields of research.