[phenixbb] regarding number of unique reflections

[Tim Gruene]

Hi Pavel, hi Viney,

you should NOT go back to data processing. Data processing should
result in unmerged data, including I+ and I-. The refinement program
(possibly under guidance of the user) should decide whether and how
data should be merged for refinement purposes. This decision should
also be reflected during data deposition when counting reflections,
however, it is best practice to deposit unmerged data. Whether or not
the PDB support deposition of unmerged data may be a different question.

Cheers,
Tim

On Wed, 12 Jan 2022 09:19:35 -0800 Pavel Afonine <pafonine at lbl.gov> wrote:

> Hi Viney,
> 
> if your data are anomalous then you expect to have Fobs+, Fobs- and 
> singletons. If your data are not anomalous, you should not have +/- 
> mates in your data set. So then the real question is: since you do
> not expect any anomalous signal and thus assume your data set isn't 
> anomalous (as you said), then how come you ended up with a data set
> that contains Fobs+, Fobs- and singletons? Perhaps you should go back
> to data processing step and make sure you don't get anomalous data
> set in the first place.
> 
> Now as to counting... Fobs+ and Fobs- are the two entries in the
> array of float values, so they are counted as two, not one (in
> Phenix).
> 
> Pavel
> 
> On 1/12/22 04:41, Viney Singh wrote:
> > Dear all,
> >
> > First of all sorry for the novice question.
> >
> > I _processed_ one of my datasets using xds. Since I was not
> > expecting an anomalous signal, I kept Friedel's Law = True.
> > The number of unique reflections I got: *17,000*
> > I used xds_ASCII.HKL after correct.LP and converted it to mtz using 
> > Phenix with 10% reflections for Rfree calculations.
> >
> > Now, when I am trying to_refine _the structure in Phenix, the 
> > structure is being refined against *32,300* reflections with *3230* 
> > reflections for Rfree calculation. Looks like refinement is
> > treating Friedel's pair as two different reflections.
> >
> > When I am trying to upload PDB on rcsb, on the refinement tab, the 
> > number of reflections used for refinement and Rfree calculations
> > are shown as 32,300 and 3220 respectively, while in the validation
> > report, no. of reflections used for Rfree calculation are shown as
> > *1700*.
> >
> > I would really appreciate if someone can guide me to resolve this 
> > discrepancy.
> >
> > Thanks in advance.
> >
> > Viney
> >
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-- 
--
Tim Gruene
Head of the Centre for X-ray Structure Analysis
Faculty of Chemistry
University of Vienna

Phone: +43-1-4277-70202

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