Figure 25.2.3.4

Brunger, A. T.; Adams, P. D.; DeLano, W. L.; Gros, P.; Grosse-Kunstleve, R. W.; Jiang, J.-S.; Pannu, N. S.; Read, R. J.; Rice, L. M.; Simonson, T.

doi:10.1107/97809553602060000724

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

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International Tables for Crystallography (2006). Vol. F. ch. 25.2, p. 713 | 1 | 2 |

Figure 25.2.3.4

A. T. Brunger,^v ^* P. D. Adams,^e W. L. DeLano,^f P. Gros,^g R. W. Grosse-Kunstleve,^e J.-S. Jiang,^h N. S. Pannu,ⁱ R. J. Read,^j L. M. Rice^k and T. Simonson^l

Figure 25.2.3.4

Examples of symbolic definition of a refinement target function and its derivatives with respect to the calculated structure-factor arrays. (a) Simultaneous refinement of heavy-atom sites of three derivatives. The target function is defined by the `target' expression. ` $[\hbox{f}\_\hbox{h}\_1]$ ', ` $[\hbox{f}\_\hbox{h}\_2]$ ' and ` $[\hbox{f}\_\hbox{h}\_3]$ ' (in bold) are complex structure factors corresponding to three sets of heavy atoms that are specified using atom selections [equation (25.2.3.7)]. The target function and its derivatives with respect to the three structure-factor arrays are defined symbolically using the structure-factor amplitudes of the native crystal, ` $[\hbox{f}\_\hbox{p}]$ ', those of the derivatives, ` $[\hbox{f}\_\hbox{ph}\_1]$ ', ` $[\hbox{f}\_\hbox{ph}\_2]$ ', ` $[\hbox{f}\_\hbox{ph}\_3]$ ', the complex structure factors of the heavy-atom models, ` $[\hbox{f}\_\hbox{h}\_1]$ ', ` $[\hbox{f}\_\hbox{h}\_2]$ ', ` $[\hbox{f}\_\hbox{h}\_3]$ ', and the corresponding lack-of-closure variances, ` $[\hbox{v}\_1]$ ', ` $[\hbox{v}\_2]$ ' and ` $[\hbox{v}\_3]$ '. The summation over the selected stucture factors (`tselection') is performed implicitly. (b) Refinement of two independent models against perfectly twinned data. `fcalc1' and `fcalc2' are complex structure factors for the models that are related by a twinning operation (in bold). The target function and its derivatives with respect to the two structure-factor arrays are explicitly defined.