Dear Hauke, when you use twin refinement, your R-factor is bound to drop whether it is twinned or not. In your case Rfree rises, which is actually hinting at your data not being twinned. How many reflections do you have in the Rfree set?
Best, Tim On Friday, October 28, 2016 1:59:29 PM CEST Hillen, Hauke wrote: > 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 > -- -- Paul Scherrer Institute Dr. Tim Gruene - persoenlich - OFLC/102 CH-5232 Villigen PSI phone: +41 (0)56 310 5297 GPG Key ID = A46BEE1A
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