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Single Particle EM

  1. José-Jesús Fernández1,
  2. José-María Valpuesta2

Published Online: 15 SEP 2009

DOI: 10.1002/9780470015902.a0021846



How to Cite

Fernández, J.-J. and Valpuesta, J.-M. 2009. Single Particle EM. eLS. .

Author Information

  1. 1

    University of Almería, Department of Computer Architecture, 04120 Almería, Spain

  2. 2

    Centro Nacional de Biotecnología – CSIC, Cantoblanco, 28049 Madrid, Spain

Publication History

  1. Published Online: 15 SEP 2009

This is not the most recent version of the article. View current version (16 MAR 2015)


Single particle electron microscopy (EM) plays an important role in structural biology because it allows derivation of biologically relevant information about proteins and macromolecular complexes. A large amount of randomly oriented images of the specimen under study (so-called particles) are collected from micrographs taken with an electron microscope. These particles are then computationally aligned and combined to yield the three-dimensional structure, which is subsequently subjected to visualization and interpretation. The resolution attained with this technique still precludes tracing of the polypeptide chain or the clear visualization of the secondary structure elements in most cases. Nevertheless, the integrative combination of the information provided by the different structural techniques (X-ray crystallography, EM and so on) at different resolution levels provides a comprehensive interpretation of the structure.

Key concepts

  • Single particle electron microscopy (EM) allows the structural determination of proteins and macromolecular complexes.

  • The combination of the structure obtained by single particle EM and the high-resolution information obtained by other structural techniques allows the derivation of biologically relevant information.

  • The biological material has to be specially prepared prior to be imaged in the electron microscope.

  • The three-dimensional structure of the specimen is determined by collecting, aligning and combining a large number of randomly oriented particles of the specimen that are extracted from the microscope images.


  • single particle electron microscopy;
  • electron cryomicroscopy;
  • structural biology;
  • image processing;
  • structure determination