Associate Professor, Department of Materials Science and Engineering, Graduate School of Engineering, Nagoya University
Single molecule measurements of bio-molecules
In the living body, bio-molecules, such as proteins, which undergo self-assembly, are part of molecular machines. They have various functions that are required for life, movement, signal processing, and the reading of genetic code. Molecular machines are dozens of nanometers in size and are made very skillfully, and it is thought that the machines operate via different mechanisms from those of artificial machines. Although a large amount of research has been done to elucidate the functions of bio-molecules, they are still not fully understood. In order to fully investigate bio-molecules, we must be able to see them directly and to manipulate them.
We are trying to determine the mechanisms of different functions, such as movement of a bio-molecule, using single molecule imaging and single molecule nano-manipulation technology that were developed recently. To measure the movement of a bio-molecule at the level of a single molecule, a measurement system, which has a resolution of one nanometer and a pico-newton order in aqueous solution, is required. However, since the equipment cannot be purchased, we are developing and using it to make actual measurements.
The bio-molecular motors that we are studying can be divided into two groups: linear motors and rotary motors. A linear motor, such as muscle contraction, moves on a rail protein, and almost all of the movements in living cells are of the linear motor type. Rotary motors can be found in bacteria, ATP synthesized enzymes, etc. and rotates using a flow of ions. We have been studying the movement on the single molecule level of these two kinds of motors. In particular, we have determined the step size of displacement, the coupled chemical reaction and load dependency for the movement of the linear motor Chara myosin.
In addition, we have determined details about the motor rotation, ion concentration dependency and the relationship between torque and rotational frequency for the bacteria flagella rotary motor. Further, by increasing the resolution of our apparatus, we plan to elucidate the energy conversion mechanism of bio-molecules.
