A high-speed atomic force microscope for studying biological macromolecules

TLDR

The atomic force microscope can image individual biological molecules in aqueous solution, but its utility is limited by the slow acquisition of high‑resolution images. The study aimed to markedly increase AFM scan speed to enable real‑time observation of biomolecular dynamics. The authors built a high‑speed scanner free of resonant vibrations up to 60 kHz, coupled it with small cantilevers (450–650 kHz resonance, 150–280 pN/nm spring constants), an objective‑lens deflection detector, and wide‑bandwidth electronics. The integrated system captures 100 × 100‑pixel images in 80 ms, producing rapid‑frame movies of biomolecules, as shown by imaging myosin V moving on mica.

Abstract

The atomic force microscope (AFM) is a powerful tool for imaging individual biological molecules attached to a substrate and placed in aqueous solution. At present, however, it is limited by the speed at which it can successively record highly resolved images. We sought to increase markedly the scan speed of the AFM, so that in the future it can be used to study the dynamic behavior of biomolecules. For this purpose, we have developed a high-speed scanner, free of resonant vibrations up to 60 kHz, small cantilevers with high resonance frequencies (450–650 kHz) and small spring constants (150–280 pN/nm), an objective-lens type of deflection detection device, and several electronic devices of wide bandwidth. Integration of these various devices has produced an AFM that can capture a 100 × 100 pixel 2 image within 80 ms and therefore can generate a movie consisting of many successive images (80-ms intervals) of a sample in aqueous solution. This is demonstrated by imaging myosin V molecules moving on mica (see http://www.s.kanazawa-u.ac.jp/phys/biophys/bmv_movie.htm ).