Figure 5
Derivative crystals of hexagonal HEWL with TPT and TaB. A stereo representation of a section of the solvent-flattened experimental electron-density map is shown calculated from SAD phases (blue mesh, contoured at 1[sigma]) together with the anomalous difference Fourier map of tungsten and tantalum (orange mesh contoured at 5[sigma]) for (a) HEWL-TPT (1.9 Å resolution) and (b) HEWL-TaB (1.9 Å resolution), respectively. HEWL is shown in stick representation; blue and purple C atoms mark two symmetry-related molecules. (a) TPT oriented by MR is shown in stick representation with light blue W and red O atoms. Owing to degradation, only 11 W atoms reside within the heavy-atom cluster, whereas additional peaks were found in the anomalous Fourier map. Black and grey arrowheads mark the positions of the missing and additional W atoms, respectively. (b) The TaB cluster at binding site 1 was found by MR at 1.8 Å resolution and is shown in stick representation. The twofold crystallographic symmetry axis is marked in red.  [article HTML]