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Re: [ccp4bb]: P21/P2 space-group ambiguity

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On Thu, 3 May 2001, Eleanor J. Dodson wrote:

>  Have you done a native patterson? If there is a strong pseudo
> translational peak with y=0.5, this will cause the 00l = 2n+1 to be
> weak.
>  Eleanor

But if the anomalous scatterers obey the y=0.5 translation (Se-Met?) you would
expect to see a strong peak in the y=0.5 harker section which apparently isn't
there. Another posibility is that you really have space group C2 which has
systematic absencenses for the odd reflection along b (and of course many
more). In this case you should see a really fat peak in the native Patterson
at 0.5 0.5 0.0. Whatever you do, and I would make this a general
recommendation, always calculate a native Patterson and a self rotation
function right after TRUNCATE. This can prevent some nasty surprizes later on
or at least give you peace of mind that all seems to behave well.



Dept. of Medical Microbiology & Immunology
University of Alberta
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