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
