Re: [ccp4bb]: refine using merged MAD data of all 3 wavelength?

["Eleanor J. Dodson" <ccp4@ysbl.york.ac.uk>]

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Yong Xiong wrote:
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> As title, I would like to know whether any one tried to use all 3 wavelength data merged/scaled
> together for the refinement. I tried this on one structure and it appeared to improve the
> refinement. I am not sure the theoretical/practical soundness of doing this. If the
> crystal is stable, it should give a lot more redudency to the data and help the high resolution
> bins. The anomalous/dispersion signals would be messed up but mostly they are not used in
> refinement any way. We could even give an average f' and f" for the merged data, or could we? Any
> comments?



 As you say - the differences in f' and f" are usually small relative to
the errors in our observations..
 Since high redundancy improves the quality of each Fhkl it is prob. in
general better to merge the lot, and accept that the Temperature factors
of the anomalous scatterers will soak up the smallish error in the
formfactor..
 However it is always better to refine against higher resolution data
than lower, and here anyway people often have one data set which goes to
a better resolution than the phasing sets.

 Eleanor
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Eleanor J.Dodson, Chemistry Department, University of York, U.K.
Tel: Home +44 (1904) 42 44 49, work:  +44 (1904) 43 25 65
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