Crystal structure oscillation photograph

A structure for AgC102 included the unusual feature of Ag-Cl bonds of length 2.20 A, so that the crystals were said to consist of AgC102 molecules rather than Ag+ and ClOj ions.61 The space group was given as Cmma, with four molecules in the unit cell, as determined from Weissenberg oscillation photographs. 

Figure 2.1 The basic steps of macromolecular crystal structure solving are illustrated with respect to the enzyme, PNP MW 30000x3 D. (a) A crystal of human PNP space group R32. (b) Monochromatic oscillation diffraction photograph recorded at the Daresbury SRS resolution limit of outermost diffraction spots =3 A. (c) Electron density map, calculated at 6 A resolution, viewed down the hexagonal c axis. The diameter of the central solvent channel is =130A. Six trimers are visible. (d) A portion of the 3 A electron density map with fitted molecular model. (e) The PNP trimer molecular model, (f) The PNP trimer with bound inhibitor the protein here is represented in ribbon format for a-helix and ft sheet (see chapter 3 for details of macromolecular structure). Based on Ealick et al (1990). These figures kindly supplied by Dr S. Ealick and reproduced with permission.

---