Multi-crystal anomalous diffraction for low-resolution macromolecular phasing

Acta Cryst. (2011). D67, 45-59 (doi.org/10.1107/S0907444910046573)

SHELXD correlation coefficients (CCall vs. CCweak) from 1000 Se substructure tries. Successful solutions (45 in red) from multi-crystal data (8 data sets here) are well separated from random solutions (rest in blue). Multi-crystal data supported structure solution whereas all single-crystal data failed.

Phase evaluations from MAD and SAD diffraction data typically require the acquisition and analysis of weak anomalous signals. Here, limitations on data accuracy, largely due to radiation damage, are overcome by carefully merging the data from several crystals. The method was tested in selenomethionyl SAD phasing of a relatively large structure (1456 ordered residues) at relatively low resolution (3.5 Å). The results show that data from multiple crystals robustly support structure determination where attempts from single-crystal data sets fail.