Biomolecular movie-making

January 7, 2013

High-speed images of proteins in action; (a) shows myosin walking on an actin filament (credit: Takayuki Uchihashi et al./Kanazawa University)

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.

Scanning electron microscope images show two different designs of cantilever tip used by Ando and co-workers for high-speed atomic force microscopy (credit: Takayuki Uchihashi et al./Kanazawa University)

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.


High-speed atomic force microscopy system (credit: Takayuki Uchihashi et al./Kanazawa University)

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.