High-Speed Atomic Force Microscopy for Studying the Dynamic Behavior of Protein Molecules at Work

In the quest for the mechanism of protein functions, various key techniques and instruments have been developed. This is an era when scrutinizing a certain protein from various angles is becoming possible through combined knowledge of its structure and function. However, it is necessary to link these different aspects of a protein along a time axis, but no technology is available for tracing a protein in action, at high spatial and temporal resolutions. Atomic force microscopy made it possible for the first time to view a nanometer-scale world in an aqueous environment. In 2001, we developed the first-generation highspeed atomic force microscope (AFM) that could capture moving protein molecules on video at 80ms/frame. Since then, we have been carrying out various efforts to increase its scan rate as well as to substantially reduce tip–sample interaction force. The reduction in this force is a key to making the high-speed AFM practically useful in life sciences. Various new techniques and devices developed in the past four years have brought the AFM to its second-generation stage. It can now capture weakly interacting protein molecules successively without disturbing their physiological function. Here, we report our efforts made over the past four years, the present capacity of the high-speed AFM, and our preliminary work on the next generation of the instrument. [DOI: 10.1143/JJAP.45.1897]