Hi Valentina,
> I just solved a NCS-tetrameric (biological assembly is just a dimer) crystal structures with ligand soak (same plate - same conditions). No density for ligand is observed in the first map. In the 2nd, I have 1 ligand bound. In the 3rd, I have 2 ligands bound. Is there any reason for this 'random' behaviour?
To _clarify_, I have 3 separate crystals; 3 datasets. Soaking time was
approximately 1 minute for all. Same ligand.
DS 1 - > no ligand
DS 2 -> 1 ligand (chain A)
DS 3 -> 2 ligands (chain A & B ; No lignad C&D).
These three datasets have
Cell from mtz : 147.0 354.3 217.4 90.0 90.0 90.0
Space group from mtz: number - 20; name - C 2 2 21
>
> In addition, I observed just one crystal out of 20 gave a different unit cell. Pointless confirms to me
> "Best Solution: space group C 2 2 2". REFMAC refinement shows R/Rfree ~ 20/25 %
> Cell from mtz : 216.5 345.8 145.2 90.0 90.0 90.0
> Space group from mtz: number - 21; name - C 2 2 2
>
> All other datasets have:
> Cell from mtz : 147.0 354.3 217.4 90.0 90.0 90.0
> Space group from mtz: number - 20; name - C 2 2 21
>
> I tried re-processing/refining the C2221 dataset in C222 but R/Rfree stays ~45%. Can I also consider the C2221 dataset as a 'different crystal form'?
>
> Am I safe?
>
> Thank you all,
> Veronica
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