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→Practical considerations
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In practice, both crystal quality and beamline quality limit the value of I/Sigma(I)<sup>asymptotic</sup>. A good crystal (even with elevated mosaicity and medium resolution) should give a high value on a good beamline. | In practice, both crystal quality and beamline quality limit the value of I/Sigma(I)<sup>asymptotic</sup>. A good crystal (even with elevated mosaicity and medium resolution) should give a high value on a good beamline. | ||
I have seen values around 15-20 for good crystals that | I have seen values around 15-20 for good crystals that allowed me to solve a MAD structure, but that required high multiplicity of observations. Values around 30 allowed me to solve a sulfur-SAD structure at medium resolution (diffraction to 2.3 A, anomalous signal to 3 A). | ||
I have also seen a value around 40 for Z. Dauter's 0.98A Proteinase K (2ID8) sulfur-SAD data from J. Holton's APS/22-ID beamline, and recently even higher values were obtained at the SLS, beamline X06SA, with a Pilatus detector. | I have also seen a value around 40 for Z. Dauter's 0.98A Proteinase K (2ID8) sulfur-SAD data from J. Holton's APS/22-ID beamline, and recently even higher values were obtained at the SLS, beamline X06SA, with a Pilatus detector. | ||