Hello Marina, In short: at first I'd build the model and refine it with the untwinned P3(2)21 data set until convergence. Then, I'd process all other data sets (including the twinned ones) in that space group as well. If using XDS, I'd use the XDS_ASCII.HKL of the untwinned data set as REFERENCE_DATA_SET for these other data sets; otherwise use POINTLESS to ensure consistent indexing (that space group has an indexing ambiguity; this often goes with merohedral twinning).
Then, refine the good model against the twinned data sets, and switch on twin refinement. If the maps show your ligand, build it into the model and continue refinement. best, Kay On Thu, 11 Jul 2019 12:50:06 +0200, Marina Ley <marina....@pharmazie.uni-marburg.de> wrote: >Hello everyone, > >I have the following problem: > >I have some really good data sets of about 1.6 A which could be >processed in P 6 2 2 as well as in P 3 2 1. >Intensity statistics tests indicate twinning (merohedral, twinning >law: -h, -k, l, in P 3 2 1). >But I did not find a good MR solution (R value around 60%) and when I >try to refine it with the twin law I get really bad maps. > >However I could get one data set where the intensity statistics tests >did not indicate twinning and I have already managed to solve the >structure. > >SPACE_GROUP_NUMBER: 154 (P 3 (2) 2 1) >UNIT_CELL_CONSTANTS: 57.56 57.56 159.98 90.000 90.000 120.000 >number of molecules in asymmetric unit: 2 >NCS: yes > >I could see a lot of amino acids in the electron density which were >not in the search model. > >But it seems like most of my crystals are twinned. For a fragment >screen which I would like to do I need to solve the twinned data sets, >otherwise I have to search again for another crystallization condition. > >I don't know what to do next to solve the twinned data sets. Do you >have any ideas or suggestions? > >Thanks in advance!!! > >Cheers, >Marina > > > >Some information about the results from Xtriage: > > ----------Statistics independent of twin laws---------- > > <I^2>/<I>^2 : 1.586 (untwinned: 2.0, perfect twin: 1.5) > <F>^2/<F^2> : 0.870 (untwinned: 0.785, perfect twin: 0.885) > <|E^2-1|> : 0.564 (untwinned: 0.736, perfect twin: 0.541) > <|L|> : 0.380 (untwinned: 0.500; perfect twin: 0.375) > <L^2> : 0.208 (untwinned: 0.333; perfect twin: 0.200) > Multivariate Z score L-test: 12.491 > > > >-- >Marina Ley > >PhD Student, Research Group Professor Dr. Klebe > >Department of Pharmaceutical Chemistry > >Philipps-University Marburg > >Marbacher Weg 6, 35032 Marburg, Germany > >Phone: +49 6421 28 21392 > >E-Mail: marina....@pharmazie.uni-marburg.de > >http://www.agklebe.de/ > >######################################################################## > >To unsubscribe from the CCP4BB list, click the following link: >https://www.jiscmail.ac.uk/cgi-bin/webadmin?SUBED1=CCP4BB&A=1 ######################################################################## To unsubscribe from the CCP4BB list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/webadmin?SUBED1=CCP4BB&A=1
