Data-collection strategy for challenging native SAD phasing.

摘要: Recent improvements in data-collection strategies have pushed the limits of native SAD (single-wavelength anomalous diffraction) phasing, a method that uses weak signal light elements naturally present macromolecules. These involve merging multiple data sets from either crystals or single crystal collected orientations at low X-ray dose. Both approaches yield high multiplicity while minimizing radiation damage and systematic error, thus ensuring accurate measurements differences. Here, combined use these two is described to solve cases phasing were particular challenges: integral membrane diacylglycerol kinase (DgkA) with Bijvoet ratio 1% large 200 kDa complex CRISPR-associated endonuclease (Cas9) bound guide RNA target DNA crystallized low-symmetry space group C2. The optimal strategy based on performed 266 kDa multiprotein/multiligand tubulin discussed.