Single molecule imaging of function of biomolecules

Biomolecules assemble to form molecular machines such as molecular motors and cell signal processors and dynamically function in response to the environmental changes in cells. The dynamic behavior of the individual biomolecules at work has been detected using recently developed single molecule measurements both in vitro and in vivo. Single molecules are visualized. Chemical reactions are monitored at the single molecule level. Conformational changes of individual protein molecules are detected. Single molecules are manipulated. These techniques have allowed the measurements of dynamic and kinetic behavior of biomolecules, which was obscured in the average values in previous ensemble measurements. The series of kinetic processes have been measured without separating each steps and synchronizing large number of molecules. It is also possible to monitor the behavior of molecules of interest exclusively in complicated systems containing variety of molecules such as cells. These measurements have demonstrated that the individual protein molecules dynamically change their locations, the interaction with other molecules and conformational and functional states. The dynamic properties of proteins provide flexibility to the system, allowing the systems to effectively respond to the stimuli. Thus the single molecule techniques have been proven to be a powerful tool to understand the unique operation of biomolecules in biosystems. [Jpn J Physiol 54 Suppl:S29 (2004)]