Over the time, methods for supramolecular polymerization has expanded, and the range of its useable monomers has diversified. In addition to plethora of molecular motifs, biomolecules such as DNA, DNA nanostructures and proteins as well as inorganic objects as unconventional monomers has recently been investigated for supramolecular polymerization. In all of these cases, monomers are in much higher size, usually several nanometers, and the non-covalent interactions varies from hydrogen bonding, host-guest and metal coordination. A notable example is Mg2+-assisted multivalent supramolecular polymerization of ATP-responsive biomolecular machines, chaperonine GroEL, resulting in a highly stable protein nanotube. Importantly, this nanotube shows an ATPase activity and dissociates into short-chain oligomers when treated with ATP because of the opening/closing motions of the constituent GroEL units.
