Molecular Machines found to be easily Manipulated using very Small Mechanical Energy

Schematic diagrams depicting the conformation of amphipathic binaphthyl and its molecular deformation caused by compression at the air-water interface. a) Pliers representing amphipathic binaphthyl (left), chemical formula of amphipathic binaphthyl (center), and three-dimensional conformation of amphipathic binaphthyl. b) and c) Schematic representation of compressed and expanded amphipathic binaphthyl molecules that are arranged in a line at the air-water interface. These forces cause conformational change similar to opening and closing pliers. Credit: Copyright NIMS

It takes advantage of the property that molecular machines aggregate on the surface of water and  will contribute to development of basic technology for operation of various molecular machines in sensors and other types of devices. The way mechanical energy works to run a machine is well understood at a macro level but due to limited quantitative methods, it had been poorly understood at the nano level, eg molecular machines, how the whole mechanical force spreads and impacts the molecular conformation and function.

We recently succeeded in taking detailed measurements on conformational change in molecules in relation to pressure exerted on them as we applied mechanical energy to molecular machines (supramolecular assembly) that aggregated at the air-water interface. In this study, we used plier-shaped binaphthyl molecules as molecular machines. At the air-water interface, binaphthyl molecules are arranged in the same orientation and aligned, forming a single-molecule-thick film. When we applied external mechanical energy to compress and expand this film by moving a partition on the surface of water, we were able to efficiently and repeatedly open and close the binaphthyl molecules. Thus, we concluded that the angle at which the molecules open and close can be controlled by applying a very small force.

To date, conformational change in molecular machines had been measured in 3D. At the 2D air-water interface, molecular arrangements are simpler. In addition, while a supramolecular assembly is very small with a thickness at only a molecular level, its area is large enough to be visible to the naked eye. As such, change in molecular conformation can be observed by precisely controlling the movement of the partition, which can be shifted manually, using machines. Based on the fact that the level of mechanical energy we applied in this study was much smaller than the levels of optical and thermal energies normally used to run molecular machines, there are high expectations on this technology for its potential to develop into a simple and energy-saving new nanotechnology. http://www.nims.go.jp/eng/news/press/2015/08/201508281.html