Roberto,

The reviewer's request is complete nonsense. The problem is how to best and 
politely respond so as not to prevent the paper from being accepted. Best would 
be to have educated editors who could simply tell you to ignore that request.

Since this issue comes up quite often still, I think we all should come up with 
a canned response to such a request.

One way to approach this issue is to avoid saying something like "the structure 
has been refined to 2.2Å resolution", but instead say "has been refined using 
data to a resolution of 2.2Å.", or even ""has been refined using data with an 
I/sigmaI > 1.5 (or whatever)". Next could be to point out that even data with 
an I/sigmaI of 1 can contain information (I actually don't have a good 
reference for this, but I'm sure someone else can provide one'), and inclusion 
of such data can improve refinement stability and speed of convergence (not 
really important in a scientific sense, though).

The point is that all of your data combined result in a structure with a 
certain resolution, pretty much no matter what high-resolution limits you 
choose (I/sigmaI of 0.5, 1.0, or 1.5). As long as you don't portrait your 
structure of having a resolution corresponding to the resolution of the 
high-resolution limit of your data, you should be fine.

Now, requesting to toss out data with I/sigmaI of <3 simply reduces the 
resolution of your structure. You could calculate two electron density maps and 
show that your structure does indeed improve when including data with /sigmaI 
of <3. One criterion could be to use the optical resolution of the structure.

Hope that helps.

Best,
MM

On Mar 3, 2011, at 6:29 AM, Roberto Battistutta wrote:

> Dear all,
> I got a reviewer comment that indicate the "need to refine the structures at 
> an appropriate resolution (I/sigmaI of >3.0), and re-submit the revised 
> coordinate files to the PDB for validation.". In the manuscript I present 
> some crystal structures determined by molecular replacement using the same 
> protein in a different space group as search model. Does anyone know the 
> origin or the theoretical basis of this "I/sigmaI >3.0" rule for an 
> appropriate resolution?
> Thanks,
> Bye,
> Roberto.
> 
> 
> Roberto Battistutta
> Associate Professor
> Department of Chemistry
> University of Padua
> via Marzolo 1, 35131 Padova - ITALY
> tel. +39.049.8275265/67
> fax. +39.049.8275239
> roberto.battistu...@unipd.it
> www.chimica.unipd.it/roberto.battistutta/
> VIMM (Venetian Institute of Molecular Medicine)
> via Orus 2, 35129 Padova - ITALY
> tel. +39.049.7923236
> fax +39.049.7923250
> www.vimm.it

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