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[[Image:Bajaj_virus-structure.jpg|400px|left|borderless]] Determining the three-dimensional structure model of a virus is the first step towards understanding its virulent function. A new experimental imaging approach utilizes cryo-Electron Microscopy (cryo-EM) for elucidating single particle macromolecular structures (such as viruses) at the highest quasiatomic resolution, typically around 10 A. In the above figure (AC) are visualizations using combined surface and volume rendering of the same half-shell model of the Rice Dwarf Virus (RDV). The different colors show the nucleo-capsid shell from the outside (A,C) and the inside (B), elucidating the local and global complexity of the quasi-symmetric packing of the individual structural protein units. Each individual structural unit, exhibiting a trimeric fold, is further visualized in (D) and (E) from two different views, as well as with different colors (F), to show the three different conformations of the monomeric protein chain forming the trimeric structure unit. All of the structure units are automatically segmented from a reconstructed 3D electron density map. Previously structural biologists have largely attempted this 3D ultrastructure elucidation steps, manually. The quasi-atomic models of these viruses and other macromolecular machines, constructed via our structure elucidation pipeline provides micro-biologists and drug discovery scientists, crucial insights into molecular interactions within macro-assemblies. The large physical size and complexity of such complexes, combined with the very low signal to noise ratio of cryo-EM, still presents significant computational and experimental challenges in this research.

Z. Yu, and C. Bajaj, <b>"Automatic ultra-structure segmentation of reconstructed cryo-EM maps of icosahedral viruses,"</b> IEEE Transactions on Image Processing: Special Issue on Molecular and Cellular Bioimaging, Vol. 14, No. 9, pp. 1324-1337. 2005.