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Leo will probably answer better than I can, but I would say I/SigI counts only the present reflection, so eliminating noise by anisotropic truncation should improve it, raising the average I/SigI in the last shell. F/sigF is expected to be better than I/sigI because dx^2 = 2Xdx, dx^2/x^2 = 2dx/x, dI/I = 2* dF/F (or approaches that in the limit . . .) On the other hand the integration software will measure spots whether they exist or not, so completeness is good even in a shell where there is no data. Anisotropic truncation removes reflections, so now calculating completeness in the outer (spherical) shell gives low completeness. In the direction where the data was truncated to 3.4 A, there are obviously no reflections in the 3.0-3.1 (e.g.) shell. Read about anisotropic truncation and scaling at the server they used: http://services.mbi.ucla.edu/anisoscale/ I think Eleanor Dodson once suggested anisotropic truncation could be preformed by a script which gets the anisotropy from the fall-off analysis in truncate, changes the cell parameters to phony ones which distort reciprocal space until falloff is the same in all directions, perform (spherical) resolution cut-off, and change the cell parameters back to the correct. I think all the refinement programs can perform anisotropic scaling, but they normally don't save the scaled data. Zhijie Li wrote: > I am little curious about the anisotropically truncated data for 3RKO: > > Percent Possible(All) 96.0 > Mean I Over Sigma(Observed) 0.8 > > In the supplementary table of the nature paper it was made clear that this 3.16-3.0A, > I/sigmaI=0.8 and Rmerge=1.216 shell was the outer shell of the anisotropically truncated > data. The authors did also report the isotropically truncated resolution to be 3.2A with > I/sigmaI=1.3 and Rmerge=73%. > > The authors also stated in the main text that > > "the best native data set was anisotropically scaled and truncated to 3.4 Å, 3.0 Å and 3.0 > Å resolution, where the F/σ ratio drops to ~2.6–2.8 along the a*, b* and c* axes, > respectively (scaling 2, Supplementary Table 1)" > > My question is, is the I/sigmaI=0.8 a consequence of many reflections with nearly 0 > I/sigmaI being included in the calculation? Then what does the 96% completeness mean? Does > it mean that 96% completeness in the spherical shell of 3.16-3.0A was achieved, by > including a great number of I=0 reflections? > > > Zhijie > > > > -------------------------------------------------- > From: "Edward A. Berry" <[log in to unmask]> > Sent: Thursday, May 31, 2012 2:59 PM > To: <[log in to unmask]> > Subject: Re: [ccp4bb] Death of Rmerge > >> Yes! I want a copy of this program RESCUT. >> >> REMARK 200 R SYM FOR SHELL (I) : 1.21700 >> I noticed structure 3RKO reported Rmerge in the last shell greater >> than 1, suggesting the police who were defending R-merge were fighting >> a losing battle. And this provides a lot of ammunition to those >> they are fighting. >> >> Jacob Keller wrote: >>> Dear Crystallographers, >>> >>> in case you have not heard, it would appear that the Rmerge statistic >>> has died as of the publication of PMID: 22628654. Ding Dong...? >>> >>> JPK >>> >>> -- >>> ******************************************* >>> Jacob Pearson Keller >>> Northwestern University >>> Medical Scientist Training Program >>> email: [log in to unmask] >>> ******************************************* >>> >