Re: [ccp4bb] Missing reflections

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Subject: Missing reflections
From: Simon Kolstoe s {- dot -} kolstoe {- at -} UCL {- dot -} AC {- dot -} UK
Date: 2008-03-12

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From: Chavas Leo ccp4hnaalas {- at -} GMAIL {- dot -} COM
Date: 2008-03-12

Subject: Re: Missing reflections
From: "George M {- dot -} Sheldrick" gsheldr {- at -} SHELX {- dot -} UNI-AC {- dot -} GWDG {- dot -} DE
Date: 2008-03-12

All these programs only refine against reflections that were actually
measured. REFMAC, but not SHELXL, provides the 'Sigma-A' weight
coefficients for Coot to use DFc instead of 2mFo-DFc for the reflections
for which Fo is not known (or is reserved for the free R) to calculate a
map. This will in general improve the appearence of the map at the cost
of introducing a little model bias. As far as I know these 'unobserved'
reflections are not used in calculating the difference map. CNS is
probably like SHELXL, I'm not sure what phenix.refine does.

George

Prof. George M. Sheldrick FRS
Dept. Structural Chemistry,
University of Goettingen,
Tammannstr. 4,
D37077 Goettingen, Germany
Tel. +49-551-39-3021 or -3068
Fax. +49-551-39-2582

On Wed, 12 Mar 2008, Simon Kolstoe wrote:

> Dear CCP4bb,
>
> I was looking through the REFMAC manual today and found the following advice:
>
> "Completing the data to include all possible hkls. Should do this after data
> reduction, and certainly before using REFMAC. This is now done with the
> uniqueify script. It is best done using CCP4i."
>
> http://www.ccp4.ac.uk/dist/html/refmac5/usage/examples.html#exam0
>
> Is it a good idea to always run uniqueify on data before running REFMAC - what
> about other refinement programs such as SHELX, CNS or phenix.refine?
>
> Simon
>

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CCP4bb <-- 2008 <-- March 2008 <-- 12 March 2008

Previous message:
Subject: Missing reflections
From: Simon Kolstoe s {- dot -} kolstoe {- at -} UCL {- dot -} AC {- dot -} UK
Date: 2008-03-12

Next message:
Subject: Re: Feature of CCP4i for 6.0.99 (SIGF/Weight label menu)
From: Chavas Leo ccp4hnaalas {- at -} GMAIL {- dot -} COM
Date: 2008-03-12