Abstract

Digital Instrument's BioScope Anyone who has ever taken the time to critically examine a walnut knows that a two-dimensional photograph fails in many respects to truly convey the unique features--the nicks, crannies, valleys, and grooves--of the walnut shell. Researchers use atomic force microscopy (AFM) to literally map the surface of inert and biological samples to obtain three-dimensional images. Whereas technological developments in microscopy1,2 have facilitated the detailed characterization and visualization of large macromolecular assemblies, AFM-generated surface topology maps can portray in explicit detail the surface features of such biological material as protein, DNA, and the membrane surface channels of cells. AFM is just one of a number of novel microscopy technologies collectively known as scanning probe microscopy (SPM). In principle, all SPM technologies are based on the interaction between a submicroscopic probe and the surface of some material. What differentiates SPM technologies is the nature of the interaction and the means by which the interaction is monitored. In electrostatic force microscopy, electrostatic interactions between probe and sample are measured as voltage gradients. By monitoring these gradients, detailed maps of the electrostatic features of a sample's surface can be created. Surfaces with active electrical currents can produce magnetic fields.