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



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ZELWER Charles wrote:
> 
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> Dear all,
> 
> We have the case of a monoclinic crystal with 0k0 systematic extinctions
> observed for k comprised between 3 and 15 and b = 70 Angstr. Other 0k0
> reflexions have not been recorded. The anomalous pattersons for two
> different anomalous scatterers support a P2 rather than a P21 space-group
> (all the peaks are in the y=0 section and the y = 0.5 section contains only
> weak peaks). Does anybody know well documented examples for which such a
> situation has been encountered? It would make us more confident in our
> interpretation. Any reference would be well appreciated.
> 
> Best Regards
> 
> Charles Zelwer


 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