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. Author manuscript; available in PMC: 2013 May 1.
Published in final edited form as: J Struct Biol. 2012 Jan 10;178(2):165–176. doi: 10.1016/j.jsb.2012.01.004

FIGURE 2.

FIGURE 2

Improvement in visualization of structural detail with averaging. Representative slices through individual cryo-electron tomograms of SIVmac239 (a) and SIV CP-MAC (b) virions. Trimeric Env spikes are distributed on the surface of the virus, as indicated by the white arrows. Alignment and 3D averaging of the density distribution of ~ 1500 individual spikes from SIVmac239 (c) or SIV CP-MAC (d) results in increased SNRs, allowing visualization of the density maps at resolutions of ~ 20 Å.