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

[Bart Hazes <bhazes@ualberta.ca>]

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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.

Bart

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