Re: [ccp4bb]: I222 to P212121

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

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"°K¤pÖr Hanna S. Yuan" wrote:
> 
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> Dear All,
> 
> I have a question not directly related to CCP4 but may be interesting to
> most crystallographers. We have a protein crystallized in I222 space
> group.  The structure was solved by MIR with one molecule per asymmetric
> unit.  Recently we crystallized the same protein in a very similar
> condition, but the space group is P212121. The unit cell dimensions of
> the P212121 cell are almost identical to those of I222. So the only
> difference is that the reflections with h+k+l=2n+1 are now present!
> 


 Have you 
  a) looked at hklview to see if the  h+k+l=2n+1 are weak
  b) done a native patterson to see if you have a strong off-origin
peak?

 I suspect you will have one at (1/2,1/2,1/2) 

Anyway if you do have a strong peak with x,y or z ~ 1/2, then you will
have absences along that axis which may not be due to space group
symmetry.

You will need to check your MR solution in all the 8 possible
orthorhombic space groups; if you are using ccp4i this is very easy -
you just change the spacegroup on the interface..

Eleanor