On Tue, 27 Aug 1996, Darren Nickerson wrote: [delitia] > I am refining a data set collected on an area detector to 1.3A. The > protein contains roughly 400 amino acids, and a cation. Isotropic > refinement gives a data to parameter ratio of roughly 5:1 (74161 unique > reflections). Data is about 65% complete in highest resolution shell. Why not collect more complete data? > I am trying to decide whether anisotropic refinement is justified at this > point, . . . R=0.183 Rfree=0.212 (isotropic). I am refining with shelx, > and have observed that refining the entire structure anisotropically > results in an approx. 4% decrease in R, but only a 2.25% decrease in > Rfree. This represents over-refinement in my mind, and so I was Why is this over-refinement? Your free-R went down! It is quite common, I think, for the freeR to decrease less than the Rcryst. No one has perfect data, after all ;-). Cheers, Aaron
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