Analyses of Functions and Interactions of Protein Molecules by Single Fluorescent Molecular Imaging

Single-molecule imaging is a useful technique for analyzing functions of proteins and protein-protein interactions. As an application of this technique, we investigated the mechanism of protein folding assisted by chaperonin GroEL. We showed that the chaperonin reaction cycle consisted of two successive timers of ~3 s and ~5 s duration. It suggested a new intermediate state that ensured efficient encapsulation of substrate protein. As another approach to study protein-protein interactions, we are now developing a microdevice that enables to sort supra-macromolecules. The solution containing organelles, of which component is fluorescent, and thermosensitive polymer was introduced to a Y-shaped microchannel. The sol-gel transition was locally induced by site directed infrared laser irradiation, resulting in plugging the microchannel and sort out the biomolecules