Oh, this is interesting. When I saw your value of 1.34, I went that's what I also see, too. By that I mean 1.34 or something very similar (once I saw a 1.36). And I do not impose any cut-offs to the I/sigma(I) or F/sigma(F) criteria, except that by default HKL2000 does a very reasonable I/s(I)>-3 cutoff, and I hope phenix.refine is not using an artificial cutoff for F/sigma(F). I have always thought that this could be a result of using truncate (French-Wilson), but was not sure. I just checked and my "truncate"d mtz's have much lower F/sigma(F)s in them, so that's not the problem. So, I have the same questions as Edward has... Engin On 2/5/12 2:02 PM, Edward A. Berry wrote:
We are depositing a structure refined by phenix, and the final pdb for deposit has the line "min Fobs/sigma=1.34".
ADIT interprets this to mean a sigma cutoff of 1.34 was used. The .eff file confirms that rejection criterion on Fobs (and on Iobs) is 0.0 .
And when I think about it, I can't see how the min Fobs/sigma could be 1.34, if the Fobs go right to zero and sigma doesn't go below some background level. So could these be lowest average of F/sigma for a shell? But we found a pdb file from another project where min Fobs/sigma=0.0, and the average for a shell wouldn't be exactly zero.
So 1)what does the "min Fobs/sigma=" line mean, and is it OK to correct ADIT with the sigma cutoff of zero?
2)Also, this is a structure containing heavy atoms (derivative was better than the native) and so refined against anomalous data. The final PDB file that was uploaded listed unique reflections with Bijvoet mates separate. Is that what we want to report? or the number after merging Bijvoet mates?
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The data.refine .mtz has I's and F's. The I's go from small negative to large positive, while the F's go from .2 or .4 (F+ and F-) to around 5000 French and Wilson truncate procedure is being used, so only about .2% reflections get rejected. However many more have negative I's. The .eff indicates a cutoff on Iobs/sigma=0. If this is applied to the I's in data.refine.mtz it will reject a lot of weak reflections and make (min F/sigma) larger- but clearly that is not happening, besides I saw min Fobs/sigma > 1 for another project in which phenix was given only F, all positive of course. _______________________________________________ phenixbb mailing list [email protected] http://phenix-online.org/mailman/listinfo/phenixbb