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Multiclass maximum-likelihood symmetry determination and motif reconstruction of 3-d helical objects from projection images for electron microscopy

Academic Article
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Overview

authors

  • Lee, S.
  • Doerschuk, P. C.
  • Johnson Jr., John

publication date

  • July 2011

journal

  • IEEE Transactions on Image Processing  Journal

abstract

  • Many micro- to nano-scale 3-D biological objects have a helical symmetry. Cryo electron microscopy provides 2-D projection images where, however, the images have low SNR and unknown projection directions. The object is described as a helical array of identical motifs, where both the parameters of the helical symmetry and the motif are unknown. Using a detailed image formation model, a maximum-likelihood estimator for the parameters of the symmetry and the 3-D motif based on images of many objects and algorithms for computing the estimate are described. The possibility that the objects are not identical but rather come from a small set of homogeneous classes is included. The first example is based on 316 128 × 100 pixel experimental images of Tobacco Mosaic Virus, has one class, and achieves 12.40-Å spatial resolution in the reconstruction. The second example is based on 400 128 × 128 pixel synthetic images of helical objects constructed from NaK ion channel pore macromolecular complexes, has two classes differing in helical symmetry, and achieves 7.84- and 7.90-Å spatial resolution in the reconstructions for the two classes.
  • Many micro- to nano-scale 3-D biological objects have a helical symmetry. Cryo electron microscopy provides 2-D projection images where, however, the images have low SNR and unknown projection directions. The object is described as a helical array of identical motifs, where both the parameters of the helical symmetry and the motif are unknown. Using a detailed image formation model, a maximum-likelihood estimator for the parameters of the symmetry and the 3-D motif based on images of many objects and algorithms for computing the estimate are described. The possibility that the objects are not identical but rather come from a small set of homogeneous classes is included. The first example is based on 316 128 � 100 pixel experimental images of Tobacco Mosaic Virus, has one class, and achieves 12.40-? spatial resolution in the reconstruction. The second example is based on 400 128 � 128 pixel synthetic images of helical objects constructed from NaK ion channel pore macromolecular complexes, has two classes differing in helical symmetry, and achieves 7.84- and 7.90-? spatial resolution in the reconstructions for the two classes.

subject areas

  • Algorithms
  • Cryoelectron Microscopy
  • Image Processing, Computer-Assisted
  • Imaging, Three-Dimensional
  • Likelihood Functions
  • Models, Molecular
  • Potassium Channels
  • Sodium Channels
  • Tobacco Mosaic Virus
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Research

keywords

  • Cryo electron microscopy (cryo EM)
  • Tobacco Mosaic Virus (TMV)
  • helical symmetry
  • image reconstruction
  • maximum-likelihood (ML)
  • tomography
  • virus
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Identity

PubMed Central ID

  • PMC3142268

International Standard Serial Number (ISSN)

  • 1057-7149

Digital Object Identifier (DOI)

  • 10.1109/tip.2011.2107329

PubMed ID

  • 21335314
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Additional Document Info

start page

  • 1962

end page

  • 1976

volume

  • 20

issue

  • 7

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