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Updated: Sep 2, 2025

Structure of HIV-1 Capsid Assemblies by Cryo-electron Microscopy and Iterative Helical Real-space Reconstruction
Published on: August 9, 2011
Escaping the symmetry trap in helical reconstruction
Lavinia Gambelli1,2, Michail N Isupov3, Bertram Daum2,4
1College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter, EX4 4QF, UK.
Abstract:
Helical reconstruction is the method of choice for obtaining 3D structures of filaments from electron cryo-microscopy (cryoEM) projections. This approach relies on applying helical symmetry parameters deduced from Fourier-Bessel or real space analysis, such as sub-tomogram averaging. While helical reconstruction continues to provide invaluable structural insights into filaments, its inherent dependence on imposing a pre-defined helical symmetry can also introduce bias. The applied helical symmetry produces structures that are infinitely straight along the filament's axis and can average out biologically important heterogeneities. Here, we describe a simple workflow aimed at overcoming these drawbacks in order to provide truer representations of filamentous structures.
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