“…Curiously, unlike self-assembling dipeptides made from aromatic amino acid such as phenylalanine, ditryptophan is unable to form ordered structures in solution [36]. However, introduction of suitable chemical modifications to augment non-covalent interactions, by employing flexible or rigid scaffolds or conjugation to other biomolecules, affords well-defined soft structures and notably, these soft structures are responsive toward external stimuli, such as presence of biologically active cations or brief exposure to sunlight [37][38][39][40][41].…”