Re: [ccp4bb]: Contour

[Jeff Taylor <jstaylor@duke.edu>]

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"Leslie A." wrote:
> 
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> "Gerard \"DVD\" Kleywegt" writes:
>  > i seriously disagree with your seriously disagreeing.
>  > assume that the sigma level at the end of a refinement
>  > is 0.0001 e/A3. then a 10-sigma feature is noise. my point
>  > is that the "number of sigmas" of a feature in an fo-fc
>  > map is meaningless - the absolute sigma level is not, of
>  > course (but this assumes that you calculate your maps on
>  > an absolute scale to begin with !).
>  >
> 
> I would suggest that your hypothetical example is not of any relevance
> to macromecular crystallography. There are ALWAYS errors in a model,
> even in the final stages of refinement, because there is never
> sufficent data to be able to model all aspects of conformational
> mobility/disorder. A 5 sigma peak in an Fo-Fc difference map, even
> close to the "end" of refinement, can be interpreted with very high
> confidence as indicating an error in the model. As I mentioned
> earlier, in many cases it may not be possible to interpret these
> features, but this does not mean they have no significance.
> 
>     Andrew Leslie

So if I follow, that annoying 5 sigma peak in my difference map is
either meaningless, or significant but not interpretable?

Now where do I put that little slider thingy?

- Jeff Taylor