Hiraoka laboratory is conducting research on molecular self-assembly.

What is molecular self-assembly?

Molecular self-assembly is a phenomenon in which constituent molecules spontaneously assemble to form an ordered structure. DNA double helices and lipid bilayers, which are components of cell membranes, are an example of molecular self-assembly in nature. Protein folding and its assembly are also molecular self-assemblies. The viral shell structure (capsid) is a complex structure in which several proteins are self-assembled. On the other hand, since the 1990s, attempts have been made to artificially create molecular self-assemblies, and many artificial self-assemblies have been reported so far. Both the self-assemblies found in nature and the ones in man-made systems are composed on building blocks that are programmed to spontaneously assemble into a certain well-ordered structure. Specifically, the information is an intermolecular interaction acting between components, which is weaker than a covalent bond. The final structure is determined by what kind of spatial arrangement is introduced into the building blocks. The environment of molecular self-assembly is also an important factor to destine the final structure. Therefore, molecular self-assembly is controlled not only by information embedded in components but also by substances outside the components.

The charm of molecular self-assembly

There are good reasons for the natural world to adopt self-assembly successfully. To create a certain substance, making chemical bonds between atoms precisely is needed. In fact, all the molecules that govern life activities are made basically through chemical bonds. However, a lot of efforts have to be maid to make very large structures by using only covalent bonds. If the building blocks are mistakenly connected by covalent bond, it is very difficult to correct it. An important keyword in molecular self-assembly is reversibility of chemical bonds. In molecular self-assembly, building blocks are connected by reversible chemical bonds, such as intermolecular interactions. Therefore, even if incorrect bonds are made, the thermodynamically most stable assembly can be formed efficiently by recombination of the chemical bonds between the building blocks. Due to this advantage, molecular self-assembly has been used not only in biological systems but also as a synthetic method for materials.