Figure 3.

Creation of a mask (PDB entry 3kcz; Karlberg et al., 2010 ▸). The 2mF _o − DF _c electron-density map corresponding to the current model is coloured blue (a). The mask, coloured orange, is created by artificially setting all modelled regions of the map to zero (b). Both maps are shown using the default contour levels in Coot. The mask is (by default) shown at a lower contour level (0.2) than the original map (0.55), emphasizing the ‘noise’ in the unmodelled regions and the fact that the masked map is set to zero in regions that have already been modelled. For reference, both masks are also shown together (c).