Dear Kay, Thank you for your answer! I have meanwhile processed my anomalous data also also as P1 and solved the structure with MR-SAD in P1, which works flawlessly and gives the same solution. Compared to P21, I now have 4 instead of 2 molecules in the ASU, which makes sense. I then tried refinement in P1 with or without applying a twin law in phenix.refine. The result seems very clear. Without twin law, R/Rfree after one round of rigid body refinement drop to 34/38. With twin refinement, the same refinement results in R/Rfree of 29/42. My current suspicion is therefore that my data are truly P1, with an NCS axis parallel to a crystallographic axis (suggested by Xtriage). Could this pseudosymmetry lead XDS to falsely identify my data as P2 instead of P1?
Best wishes, Hauke ------------------------------------------------------- Hauke Hillen Department of Molecular Biology Prof. Dr. Patrick Cramer Max-Planck-Institute for Biophysical Chemistry Am Fassberg 11 D-37077 Göttingen Germany E-Mail: hauke.hil...@mpibpc.mpg.de<mailto:hauke.hil...@mpibpc.mpg.de> Phone: +49-551-201-2864 On Oct 28, 2016, at 3:51 PM, Kay Diederichs <kay.diederi...@uni-konstanz.de<mailto:kay.diederi...@uni-konstanz.de>> wrote: Dear Hauke, the conversion of intensities to amplitudes is an area with unsatisfactory solutions, and the approaches of (and the assumptions made by) the different programs differ. Low-resolution data are often anisotropic, which adds difficulties. You could try CCP4 truncate/ctruncate and GlobalPhasing's staraniso. The latter in particular should treat anisotropic diffraction more properly. Probably you get yet other answers from xtriage when fed with those amplitudes. Possibly this will add to the confusion, but I'm not sure it is worth worrying about this too much. Having said that, it seems to me like the primary and most unspoiled data are the intensities. I don't see anything suspicious in the xtriage-on-intensities output that you posted. good luck with your difficult project! Kay
