These two images depict the outer shell or capsid of the phi
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These two images depict the outer shell, or "capsid," of the phi 29 virus

June 8, 2010
These two images depict the outer shell, or "capsid," of the phi 29 virus, which attacks the soil bacterium bacillus subtilis. The figure on the left shows the protein structure of the capsid, and the figure on the right overlays that structure on an "electron density map" of the outer shell created with a powerful imaging technique called cryo-electron microscopy. Purdue University researchers used the technique to determine the capsid's three-dimensional structure at nearly atomic-scale resolution. The scientists discovered that phi 29's capsid contains the same "fold" as another virus, called HK97, both of which split from a common ancestor possibly a billion years ago. The findings help to reinforce theories about how viruses have evolved over millions of years.

This is generally NSF funded research aimed at understanding the structures of viruses. Many people were involved in this research in different capacities, including Marc C. Morais, Kyung H. Choi, Joya S. Koti, Paul R. Chipman, Dwight L. Anderson and Michael G. Rossmann. [One of three related images. See Next Image.] (Date of Image: May 2, 2005)

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