Constitutionally Isomeric Aromatic Tripeptides: Self‐Assembly and Metal‐Ion‐Modulated Transformations.

Self‐assembling peptides based on aromatic amino acids can adopt diverse nanostructures which primarily depend on their molecular structures. Therefore, to understand the nature of self‐assembly on the molecular level we rationally designed two constitutional isomers of short aromatic peptides. The first isomer consists of a tyrosine moiety at the N‐terminus and the second isomer consists of a tyrosine moiety at the C‐terminus of the FF peptide, a core recognition motif of Amyloid β peptides. Therefore, it can be considered that both the designed tripeptides are the analogues of the FFF peptide with only atomic(−H) level replacement by −OH functional group on the first and last phenyl ring, respectively. The first isomer self‐assembled into 2D porous nanosheets ("Nanowebs"), however the second isomers produced toroidal shapes with central spheres ("Nano‐Saturn" like assemblies). Interestingly, the presence of the transition‐metal ions (copper, zinc and iron) triggered the self‐assembly of both the peptides into fibrous circular discs, nanomats and nanoplates like assembly. [ABSTRACT FROM AUTHOR]