January 7, 2013
Toshio Ando and co-workers at Kanazawa University have developed and used high-speed atomic force microscopy (HS-AFM) to achieve direct visualization of dynamic structural changes and processes of functioning biological molecules in physiological solution — creating microscopic movies of unprecedented sub-100-ms temporal resolution and submolecular spatial resolution.
To produce an image, HS-AFM acquires information on sample height at many points by tapping the sample with the sharp tip of a tiny cantilever and dragging the sharp tip of a tiny cantilever across the sample. Depending on the application, this might involve recording the distance of deflection, the amplitude and phase of oscillations, or the resonant frequency of the cantilever.
Ando and co-workers use very small cantilevers that provide 10 to 20 times the sensitivity of larger, conventional cantilevers. Copies of their home-made apparatus are now commercially available through the manufacturer Research Institute of Biomolecule Metrology Co., Ltd in Tsukuba, and record images at least ten times more quickly than their competitors.
In their paper, published in Nature Protocols, the researchers describe how to prepare substrates to hold samples during HS-AFM, and provide advice on the best ways to take advantage of the equipment.
These methods have so far enabled the team to record cargo-carrying proteins “walking” on up cell filaments, the rotational motion of motor proteins that provide energy in cells, and the hydrolysis of cellulose.