Resolution vs. Electron Density Maps


The electron density maps at right* (contoured at 1 sigma) show how resolution affects the fit of the map to the atomic structure, for resolutions of 5.0, 3.5, 2.5, 1.4 and 0.5 Ångstroms. These are "perfect" electron density maps calculated from the atomic model (R factor = 0.0%, perfect phases and amplitudes). Electron density maps based on experimental data would fit the true conformation less well.

See The Movie!
(Click on The Importance of Resolution.)

2.05 Å is the median resolution for X-ray crystallographic results in the Protein Data Bank (43,066 on May 2, 2008). Here is the distribution:
  •  0.14%   (60): >=5.0 Å
  •  1.1%   (488): 3.5 - 4.99 Å
  • 23%  (10,096): 2.5 - 3.49 Å
  • 70%  (30,037): 1.4 - 2.49 Å
  •  4.3% (1,867): <= 1.39 Å
  •  0.5%   (209): <= 1.0 Å
  •           (8): <= 0.7 Å
*Credit: These images are taken from a movie created by James Holton at the Advanced Light Source of the Berkeley Laboratory at the University of California. See Holton's other very informative movies about X-ray diffraction and model building.

See also