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 OiK and O~BFS, both of which belong to space group I23. Statistical disorder in the O, G67 crystals means, however, that the measured iffrac-tion data possess higher symmetry consistent with point group 432. It is shown that this is due to intimate twinning, with mosaic blocks randomly dis-tributed between the two orientations. This results in a twofold loss of information due to the exact super-imposition 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 applica-tions are discussed. Abbreviations FMDV, foot-and-mouth disease virus. 1F231, 123 structure-factor amplitude. 23]Fmutantl, estimate of 123 structure-factor amplitude for G67 produced by back-transformation of averaged/flattened map or by re-scaling of the esti-mates so derived. IF432[, I432 structure-factor amplitude. Funfo~ded estimate of G67 space group 123 mutant, structure-factor amplitude produced by duplicating 1432 amplitudes so that I Fhkll = I Fkh/I. F unfolded parent I, as above but for the parental virus model. aparent, phase estimates for the parental virus