Dear Peer,
Have you looked at your images to check whether there is streakiness in
some parts of the diffraction pattern? You could have a case of lattice
translocation disorder, a nuisance often associated with tNCS but for which
there are remedial methods available.
With best wishes,
Gerard.
On Thu, Aug 26, 2021 at 11:54:06AM +0200, Peer Mittl wrote:
> Der CCP4 community,
>
> Is there a refinement program that can handle protein monomers sitting on
> crystallographic 2-folds?
>
> This is probably a strange question but we have the following situation. We
> have a 2.6 Ang datasets in SG P3221 (Rpim=4%, Isa=19.6) and a clear molrep
> solution with 2 chains, albeit with tNCS (0/0/0.5) that can be refined to
> around 27/33% Rfactor. According to Vm a third chain could be present. So
> far so good, but there is clear difference ED for a third chain sitting
> exactly on the 2-fold. Since the protein has a peculiar shape, one can tell
> even its orientation. I can relax the symmetry to P32 (or even P1) and place
> the missing chain with 50% occupancy on the 2-fold. This model can be
> refined, but I do not like this work around, because the data is clearly
> P3221.
>
> Any hints on similar crystal pathologies and how they have been handled
> would be helpful.
>
> All the best,
> Peer
>
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