It is well known that Rmerge is a terrible criterion for determining a resolution cutoff, see eg
P.A.Karplus,K.Diederichs,Science336,1030(2012)
As the intensities get weaker at high resolution, Rmerge tends to infinity, with no sensible cutoff. CC(1/2) is generally considered the best criterion for this, at present anyway. Rmerge of 1.59 in the outer shell is perfectly acceptable, CC(1/2) in the outer shell is 0.645 which is still good (maybe the data go a little beyond there?)
On the other hand, a high Rmerge (or low CC(1/2)) at low resolution, or in the top intensity bin, is a indicator of something seriously wrong, some horrible systematic error or instability. In your innermost resolution bin, the Rmerge values are rather high (what are Norm R-fac and Linear R-fac?), and CC(1/2) is a little low
You need to look at other things, notably radiation damage
But if the structure tells you what you want know, enjoy it!
Phil
> On 28 Sep 2018, at 09:09, Zhang Foggy <[log in to unmask]> wrote:
>
> Dear All,
>
> Sorry for the off-topic.
>
> I recently collected a set of data. The diffraction spots are extremely sharp. However, When I used HKL3000 to scale it, I get a final resolution at 3.1A with overall R-merge ~0.54 (R-merge in the highest 3.2A-3.1A shell: 1.59). Then I solve the structure with final R value 0.19 and R free value 0.24 although I know this Rmerge value is totally unacceptable, and the density looks perfect.
>
> I also tried to collect other four set of data with different crystals. unfortunately, all of them have same problem.
>
> I ask one of my friend who is an expert in HKL3000, but he had no idea about it. Does anyone has suggestions?
>
> Here is the scale information for your review:
> Space group: P43 (I also tried P1, the Rmerge value is still similar)
>
> Shell Lower Upper Average Average Norm. Linear Square
> limit Angstrom I error stat. Chi**2 R-fac R-fac Rmeas Rpim CC1/2 CC*
> 50.00 6.67 11.6 0.9 0.3 1.165 0.191 0.284 0.198 0.052 0.975 0.994
> 6.67 5.30 4.5 0.5 0.3 0.952 0.317 0.313 0.329 0.086 0.971 0.993
> 5.30 4.63 7.3 0.7 0.5 0.961 0.293 0.297 0.304 0.081 0.975 0.994
> 4.63 4.21 7.0 0.8 0.6 0.986 0.369 0.358 0.382 0.101 0.969 0.992
> 4.21 3.91 5.6 0.8 0.6 1.040 0.522 0.491 0.541 0.142 0.955 0.988
> 3.91 3.68 4.6 0.9 0.7 1.064 0.718 0.669 0.746 0.203 0.929 0.981
> 3.68 3.49 3.5 0.9 0.8 1.092 1.059 0.986 1.101 0.299 0.882 0.968
> 3.49 3.34 2.6 0.9 0.8 1.092 1.382 1.298 1.438 0.395 0.829 0.952
> 3.34 3.21 2.1 0.9 0.8 1.084 1.543 1.489 1.614 0.468 0.772 0.933
> 3.21 3.10 1.6 0.9 0.8 1.070 1.591 1.669 1.680 0.529 0.645 0.885
> All reflections 5.0 0.8 0.6 1.048 0.538 0.487 0.559 0.153
>
> Thank you.
>
> Liang
>
>
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