International
Tables for Crystallography Volume F Crystallography of biological macromolecules Edited by E. Arnold, D. M. Himmel and M. G. Rossmann © International Union of Crystallography 2012 |
International Tables for Crystallography (2012). Vol. F, ch. 15.3, pp. 409-410
Section 15.3.4.3. Phase-extension schemes^{a}Department of Chemistry, University of York, York YO1 5DD, England,^{b}Division of Basic Sciences, Fred Hutchinson Cancer Research Center, 1100 Fairview Ave N., Seattle, WA 90109, USA, and ^{c}Department of Physics, University of York, York YO1 5DD, England |
When performing phase extension, the order in which the structure factors are included will affect the final accuracy of the extended phases. The phases obtained from previous cycles of phase extension will be included in the calculation of new phases for the unphased structure factors in the next cycle. A reflection with more accurately determined phases might enhance the phase-extension power of the original set of reflections, whereas a reflection with less accurately determined phases might corrupt the phase-extension power of the original set of reflections and make the phase extension deteriorate quickly. The factors that might affect phase extension are the structure-factor amplitudes, the resolution shell and the figure of merit. Based on the above considerations, the following phase-extension schemes are provided in DM: