Re: [ccp4bb]: anomolous difference maps

["Eleanor J. Dodson" <ccp4@ysbl.york.ac.uk>]

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Maneesh Yadav wrote:
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> 
> Hi all,
> I was wondering if someone would mind explaining how I generate an
> anomolous difference map in CCP4 starting from an MTZ file...
> 
> I know that the F+ and F- are preserved in the MTZ (from d*trek) but their
> precise relation to the DANO labels eludes me...


  DANO = F+ - F- ; SIGDANO = SQRT ( SIGF+ **2 + SIGF- **2)/2)

> Trying to use FFT and supplying the MTZ just gives me a big volume of
> 0's...
>  


  Input fft hklin ...
LABI DANO = Dano PHI=??? W= ????

The DANO label sigmnals that all phases must be advanced ( or is it 
retarded - look in the documentation..) by 90

I know it works!

  Eleanor
> I did generate the map with CNS, and I know the signal is there (iodine
> peaks from iodobenzene), but I would like to be consistent in my analysis
> sticking with CCP4.
>  
> Many Thanks,
> Maneesh Yadav
> 
> 
> 
>