Re: [ccp4bb]: FALLOFF warnings from truncate

[Martyn Symmons <martyn@cryst.bioc.cam.ac.uk>]

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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
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