Deconvolution of fully overlapped reflections from crystals of foot-and-mouth disease virus O₁ G67

Foot-and-mouth disease virus O₁ G67 forms crystals that appear similar to those of the closely related viruses O₁K and O₁BFS, both of which belong to space group I23. Statistical disorder in the O₁ G67 crystals means, however, that the measured diffraction data possess higher symmetry consistent with point group 432. It is shown that this is due to intimate twinning, with mosaic blocks randomly distributed between the two orientations. This results in a twofold loss of information due to the exact superimposition of non-identical reflections from the two orientations. A simple procedure has been devised to deconvolute these overlapped reflections by applying constraints in both real and reciprocal space. This procedure works well, providing interpretable electron-density maps for this virus. Other applications are discussed.