Chapter 16.3 Ab initio phasing of low‐resolution Fourier syntheses

Crystallography of biological macromolecules

Second Online Edition (2012)

Part 16. Direct methods

  1. V. Y. Lunin1,
  2. A. G. Urzhumtsev2,
  3. A. Podjarny3

Published Online: 14 APR 2012

DOI: 10.1107/97809553602060000852

International Tables for Crystallography

International Tables for Crystallography

How to Cite

Lunin, V. Y., Urzhumtsev, A. G. and Podjarny, A. 2012. Ab initio phasing of low‐resolution Fourier syntheses. International Tables for Crystallography. F:16:16.3:437–442.

Author Information

  1. 1

    Laboratory of Macromolecular Crystallography, Institute of Mathematical Problems of Biology of the Russian Academy of Sciences, Institutskaia, 4 Region Russia, Pushchino, Moscow Region142290, Russian Federation

  2. 2

    Faculty of Sciences, University of Nancy 1, Vandoeuvre‐lès‐Nancy, 54506, France

  3. 3

    Structural Biology, IGBMC, BP 163 Cedex, Illkirch, 67404, France

Publication History

  1. Published Online: 14 APR 2012



Low‐resolution phasing addresses the cases where experimental X‐ray diffraction intensities are only available to a low‐resolution limit, or when the standard phasing methods to solve macromolecular structures fail. Ab initio phasing is based on general properties of macromolecular objects (connectivity, electron‐density histograms, likelihood of molecular masks etc.) and does not require extra diffraction experiments. The Monte Carlo phasing procedure includes generation of a large ‘population’ of trial solutions, enrichment of this population by filtering with selection criteria, clustering and averaging. The results of low‐resolution phasing allow one to get information on the packing of particles in a crystal and on the shape (envelope) of the molecules, and to get an insight into the architecture of multidomain complexes.


  • low‐resolution phasing;
  • ab initio phasing;
  • low‐resolution images;
  • multifiltering cyclic phasing procedure;
  • map connectivity;
  • few‐atoms model;
  • phase averaging;
  • Fourier synthesis;
  • cluster analysis