Atomic force microscopy: a powerful tool to observe biomolecules at work.

Atomic force microscopes (AFMs) move a sharp tip attached to a soft cantilever in a TV-raster-like pattern over a surface and record deflections of the tip that correspond to the surface topography. When operated in physiological solutions, an AFM allows biomolecules to be observed in their native environment. Progress in instrumentation, sample-preparation methods and recording conditions has provided images of biomolecules and their assemblies that reveal submolecular details. In addition, the AFM allows conformational changes to be observed directly. This article discusses these points and illustrates them with some pertinent examples.