Structural studies of viruses by electron cryomicroscopy.

Electron cryomicroscopy is a unique biophysical technique for studying molecular structures of viruses which are difficult to analyze by x-ray diffraction. The structural information derived from the low resolution reconstructions of viruses has so far been useful to understand various functional properties of the viruses such as antibody neutralization, receptor binding and assembly. Electron cryomicroscopy has enabled the visualization of the four core alpha helices of the coat protein in tobacco mosaic virus. This represents the highest resolution detail of a virus studied by electron cryomicroscopy. The prospects of attaining similar resolution beyond 10 A for spherical viruses as well are encouraging, with newly available instrumentation, data collection and processing procedures.