International
Tables for Crystallography Volume F Crystallography of biological macromolecules Edited by M. G. Rossmann and E. Arnold © International Union of Crystallography 2006 |
International Tables for Crystallography (2006). Vol. F. ch. 25.2, p. 722
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If the coordinates of one or a few heavy atoms are known, initial phases can be calculated. The problem of solving the structure of such a metalloprotein from the sites of the metal alone can be considered in the same framework as for heavy-atom-replacement solutions. Maps calculated from the phases of heavy atoms alone often have the best defined features within a defined radius of the heavy atom(s). Thus protocols that do not place all atoms at the start but instead perform a slow building while extending the model in a growing sphere around the heavy atom are preferred. When such a model is essentially complete, it can be used for automated tracing and completion of the model.