play an essential role in the assembly of secondary and tertiary structures of large biomolecules. DNA double helix is formed by hydrogen bonding between nucleobases: adenine and thymine forms two hydrogen bonds, while guanine and cytosine forms three hydrogen bonds (Figure "Hydrogen bonds in (a) DNA duplex formation"). Another prominent example of hydrogen bond-assisted assembly in nature is the formation of protein secondary structures. Both the α-helix and β-sheet are formed through hydrogen bonding between the amide hydrogen and the amide carbonyl oxygen (Figure "Hydrogen bonds in (b) protein β-sheet structure"). In supramolecular chemistry, hydrogen bonds have been broadly applied to crystal engineering, molecular recognition, and catalysis. Hydrogen bonds are among the mostly used synthons in bottom-up approach to engineering molecular interactions in crystals. Representative hydrogen bond patterns for supramolecular assembly is shown in Figure "Representative hydrogen bond patterns in supramolecular assembly". A 1: 1 mixture of cyanuric acid and melamine forms crystal with a highly dense hydrogen-bonding network. This supramolecular aggregates has been used as templates to engineering other crystal structures. Applications Supramolecular assemblies have no specific applications but are the subject of many intriguing reactions. A supramolecular assembly of peptide amphiphiles in the form of nanofibers has been shown to promote the growth of neurons. An advantage to this supramolecular approach is that the nanofibers will degrade back into the individual peptide molecules that can be broken down by the body. By self-assembling of dendritic dipeptides, hollow cylinders can be produced. The cylindrical assemblies possess internal helical order and self-organize into columnar liquid crystalline lattices. When inserted into vesicular membranes, the porous cylindrical assemblies mediate transport of protons across the membrane. Self-assembly of dendrons generates arrays of nanowires. Electron donor-acceptor complexes comprise the core of the cylindrical supramolecular assemblies, which further self-organize into two-dimensional columnar liquid crystalline lattices. Each cylindrical supramolecular assembly functions as an individual wire. High charge carrier mobilities for holes and electrons were obtained. See also Molecular self-assembly Host–guest chemistry Supramolecular chemistry Crystal engineering References Nanotechnology Supramolecular chemistry Soft matter Self-organization ja:超分子