“…Hydrogen bonds are most suitable for this purpose. Prominent examples are the chains formed by molecules with two ureopyrimidine (upy) end groups [6], by bisureas with pendant hydrophobic groups [7][8], by small peptides in solvents of low polarity [9][10], by peptides with an alkyl 'tail' [11][12], or by folded polypeptides [13][14]. Also, coordination bonds can do the job, e.g., the combination of a bis-ligand with appropriate metal ions in water [15][16][17].…”