Identification of the point of diminishing returns in high-multiplicity data collection for sulfur SAD phasing

摘要: High-quality high-multiplicity X-ray diffraction data were collected on five different crystals of thaumatin using a homogeneous-profile beam at E = 8 keV to investigate the counteracting effects increased multiplicity and radiation damage quality anomalous macromolecular crystals. By comparing sulfur substructures obtained from subsets selected as function absorbed dose with positions in respective refined reference structures, doses which highest differences could be identified for A statistic σ{ΔF}D, calculated width σ normalized distribution set {ΔF} D, is suggested measure dose. An empirical rule proposed identify gains due are outbalanced by losses decreases signal-to-noise consequence damage. Identifying this point diminishing returns allows optimization choice collection parameters selection used subsequent crystal structure determination steps.