International
Tables for
Crystallography
Volume F
Crystallography of biological macromolecules
Edited by M. G. Rossmann and E. Arnold

International Tables for Crystallography (2006). Vol. F, ch. 16.1, p. 337   | 1 | 2 |

Figure 16.1.7.1 

G. M. Sheldrick,c H. A. Hauptman,b C. M. Weeks,b* R. Millerb and I. Usóna

aInstitut für Anorganisch Chemie, Universität Göttingen, Tammannstrasse 4, D-37077 Göttingen, Germany,bHauptman–Woodward Medical Research Institute, Inc., 73 High Street, Buffalo, NY 14203-1196, USA, and cLehrstuhl für Strukturchemie, Universität Göttingen, Tammannstrasse 4, D-37077 Göttingen, Germany
Correspondence e-mail:  weeks@orion.hwi.buffalo.edu

[Figure 16.1.7.1]
Figure 16.1.7.1

A flowchart for the Shake-and-Bake procedure, which is implemented in both SnB and SHELXD. The essence of the method is the dual-space approach of refining trial structures as they shuttle between real and reciprocal space. In the general case, steps 7 and 12 are any density-modification procedure, and steps 9 and 14 are inverse Fourier transforms rather than structure-factor calculations. The optional steps 8 and 13 take the form of iterative peaklist optimization or random omit maps in SHELXD. Any suitable starting model can be used in step 3, and SHELXD attempts to improve on random models (when possible) by utilizing Patterson-based information. Step 4 is bypassed if phase sets (random or otherwise) provide the starting point for the dual-space loop. SHELXD enters the real-space loop if the FOM (correlation coefficient) is within a specified threshold (1–5%) of the best value so far.