J. Synchrotron Rad. (2007). 14, 34-42 [ doi:10.1107/S0909049506038970 ]
Abstract: Site-specific radiation damage on anomalously scattering sites can be used to generate additional phase information in standard single- or multi-wavelength anomalous diffraction (SAD or MAD) experiments. In this approach the data are kept unmerged, down to the Harker construction, and the evolution of site-specific radiation damage as a function of X-ray irradiation is explicitly modelled and refined in real space. Phasing power is generated through the intensity differences of symmetry-related reflections or repeated measurements of the same reflection recorded at different X-ray doses. In the present communication the fundamentals of this approach are reviewed and different models for the description of site-specific radiation damage are presented. It is shown that, in more difficult situations, overall radiation damage may unfold on a time scale that is similar to the evolution of site-specific radiation damage or to the total time that is required to record a complete data set. In such cases the quality of the phases will ultimately be limited by the effects of overall radiation damage.
Keywords: radiation damage; MAD phasing; heavy-atom refinement.
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