Re: [ccp4bb]: FALLOFF warnings from truncate

[Edward Berry <eaberry@lbl.gov>]

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Unlike the refinement process, the calculation of R and R-free are not 
weighted by sigma. So scaling up all those weak reflections will make them
contribute more to R and R-free, I should think. Not that anyone should 
choose a refinement strategy simply to get better statistics!

Ed



Martyn Symmons wrote:
> 
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> 
> Dear Pedro
>           once you have a model then refinement programs can apply an
> anisotropic correction to the data to get a good fit between Fcalc and
> Fobs - they usually do this on the fly so your data stays unchanged. If
> you do want to make it stick then you can use SFALL to calculate Fcalcs
> and then use SCALEIT to scale the FPs to these Fcalcs (by telling it that
> your native is a heavy atom derivative...). Or if you have some other
> estimate of the Bfactor matrix (say whatever the refinement program tells
> you _it_ applied) then you can apply it directly in SCALEIT. I guess that
> this is looked on as dubious practice since you are cooking up new FPs -
> but of course SCALEIT keeps track of the sigmaFPs and so the larger
> relative errors in the weak data keep everything in proportion....
>         I have to admit to having done this before SIGMAA and DM which
> don't do anisotropic corrections for themselves. But that is just between
> me and you, ok? (oops - should have edited that Cc line....)
>          good luck with everything
>               Martyn
> 
> Martyn F. Symmons
> Research Associate
> Crystallography and Biocomputing Group
> Department of Biochemistry
> University of Cambridge
> Phone: 01223 766020
> -----------------------
> "Am fear a ghleidheas a theanga,
>  gleidhidh e a charaid."
> Seanfhacal Gaidhlig (Gaelic Proverb).