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Dear Hamid,
the statistics for I/sigI and the R-value per resolution shell would
shed more light than the overall values.
Judging from the Rmerge in the high resolution shell the data may have
been processed by somebody who still thinks Rmerge <= 30% is a good
criterium for resolution cut-off.
The high overall Rmerge might indicate a wrong space-group was picked
with too high symmetry.
If you have a copy of the unmerged data, run it through pointless, if
you even have a copy of the frames, reprocess them in P1 and run the
data through pointless!
If these data are from an article you are refereeing please point out
that Rmerge should not be published anymore and be replaced by Rmeas
(alias Rrim)!
Best,
Tim Gruene
On 03/29/2013 02:19 PM, hamid khan wrote:
> Dear CCP4BB Members,
>
>
>
> I am interested in your expert comments/opinions about two values
> of a protein crystal diffraction data. Basically I am new to this
> field and do not have much idea about diffraction data
> interpretation and crystallography software’s use.
>
>
>
> 1) What could be the possible reasons for a high Rmerge value, say
> like 0.185?
>
>
>
> 2) Value 6.2 for average I/sigma(I) for higher shell means that
> the resolution of the diffraction data is much higher than actually
> measured, what could be the possible reasons for this?
>
>
>
> For your ease I would like to past the table here;
>
>
>
> Values in parentheses are for the last resolution shell
>
> Space group P2221
>
> Unit-cell parameters (A°)
>
> a 58.08
>
> b 101.32
>
> c 103.47
>
> Molecules in ASU 1
>
> Resolution range 38.63 - 2.50 (2.59 - 2.50)
>
> Total number of reflections 228902
>
> Number of unique reflections 21600
>
> Completeness (%) 99.1 (98.0)
>
> Rmerge 0.185
> (0.373)
>
> Reduced χ2 0.94 (1.01)
>
> Average I/σ(I) 9.8
> (6.2)
>
>
>
> Thanks for the tips..,
>
>
> Hamid Khan
- --
Dr Tim Gruene
Institut fuer anorganische Chemie
Tammannstr. 4
D-37077 Goettingen
GPG Key ID = A46BEE1A
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