Figure 2
SAD- and SIRAS-based structure determination in P212121. (a) Electron density calculated from SAD phases based on the 1–180° data together with the final Nb36-C85-1 model. (b) As in (a) but after density modification. (c) The map calculated with SIRAS phases prepared using the 1–180° data as a derivative with anomalous signal and the 180–720° wedge as native data. (d) As in (c) but after density modification. (a)–(d) are contoured at 1.2σ. (e) Close-up of a Hg atom inserted between two NCS-related Cys85 side chains together with an anomalous map calculated with the anomalous differences from the 1–180° data and phases derived from the final model with Hg atoms and water molecules omitted. One minor site (marked with an asterisk) is already present in this wedge of data. (f) Anomalous map calculated from the anomalous differences in the 180–720° data revealing how the Hg site is splitting into one major and two minor sites. (g) Difference mFo− DFc map calculated after omission of the Hg atoms and all water molecules from the final model based on the 1–180° data. The maps in (e) and (f) are contoured at 5σ, while the difference map in (g) is displayed at 3σ. Water molecules are shown as red spheres. |