Dear Gabriel,
Couldn't it simply be that your two crystals were indexed differently?
If you could give their respective cell parameters, it will be possible to
tell whether this is the case.
With best wishes,
Gerard.
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On Wed, Jan 22, 2014 at 12:50:03PM -0800, Gabriel Moreno wrote:
> Dear CCP4 Contributors,
>
> I have a bit of a mystery:
>
> Two co-crystals that I picked up from the same grid tray (the two
> conditions vary slightly in %PEG and [salt], both indexed as P1 (apo
> structure normally crystallizes in P3221). One dataset was indexed,
> integrated and scaled with HKL2000. The other was processed with MOSFILM
> (could not process in HKL2000). Downstream processing for both sets was
> done exactly the same in PHENIX. Though both asymmetric units contain two
> complete tetramers, the interesting thing is that the configuration of
> monomers is different between the solutions. One contains one complete
> tetramer, one trimer (with a void where the fourth monomer would be), and
> one monomer on off on its own. The asymmetric unit of the other dataset
> solution also contains a complete tetramer, but then has two dimers. Close
> analysis of contacts between symmetrically related molecules reveals that
> the crystal packing is exactly the same between the two solutions from the
> two datasets. Also, the Rwork and Rfree for both models are 0.18 and 0.20.
> Other quality indices are also comparable between the two sets.
>
> Here's my question: Does this phenomenon reveal anything important, or is
> this type of thing just seen sometimes with P1 solutions from crystals of
> the same protein and condition (more or less).
>
> I hope I have been clear.
>
> Thanks!
>
> Gabriel
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