ABSTRACT
Scanning probe microscopes (SPMs) are widely used in the
materials science and nanotechnology fields to observe and inspect
nanometer-size structures. They are also indispensable tools in the
biological research community. The range of operation of SPMs is
well suited for characterizing structures from the molecular to the
cellular scale, and the unique ability of an SPM to sensitively detect
molecular forces provides a potent approach to the elucidation of the
mechanisms of interactions between biomolecules. Furthermore,
the ability to operate in an aqueous environment, without the
need for sample treatment, has made the AFM ideal for use in
investigating biological samples such as proteins, nucleic acids,
and even living cells/tissues under physiological conditions. This
remarkable advantage has made it possible for the dynamic
processes of enzymatic reactions [1-4] and morphological changes
of living cells [5-8] to be studied. However, the slow data acquisition
rate of earlier models of conventional AFM (several seconds to
minutes per frame) limited the time resolution of the biological
events requiring a subsecond time scale. Thus, most physiological
reactions had remained undetectable until Ando et al. successfully
developed a high-speed AFM capable of imaging at a scanning
rate of >1 frame per second (fps) (see details in chapter 8 and
Ref. [9]). Various applications of this device have quickly appeared
in the last decade. Conformational changes of proteins [10-13],
reaction mechanisms of DNA-targeting enzymes (Chapter 13 and
Ref. [14-17]), and the dynamic behavior of motor proteins (Chapter
8 and Ref. [18]) and nucleosomes [19, 20] have been addressed
by the high-speed AFM. It is noteworthy that, presently, both the
“subsecond time frame” and the “nanometer scale” single-molecule
observations of functional biological macromolecules cannot be
achieved by other techniques.
