Hi everyone, I have a dimmer protein diffract to 1.6 A resolution. After processing the data, the Linear R-fac was 0.26/0.038 (last/all), the data quality seems good. This data can be processed to P3 or P321 with the R-fac almost the same After that, I used Bales to do the MR, two solutions were found in P32 (dimmer) and one in P32 21 (monomer) Then, I refine the structure using phenix.refine in both P32 and P32 21 sets, but the R/Rfree stopped at 0.19/0.25 and never goes down. Rfree 25% seems a little bit too high for a 1.6 resolution data. However, if I treat the P32 data as a twin (with twin law h,-h-k,-l ), the R/Rfree can down to 0.12/0.18. I use P3 to run the phenix.xtriage (see bellows), it looks like the L-test says it is not a twin data. So, I am wondering is it a twin data or not? The results are as follow. "Twinning and intensity statistics summary (acentric data): --------------------------------------------------------------------------- Statistics independent of twin laws - /<I>^2 : 2.105 - <F>^2/ : 0.773 - <|E^2-1|> : 0.757 - <|L|>, : 0.508, 0.344 Multivariate Z score L-test: 2.013 Statistics depending on twin laws ------------------------------------------------------------------ | Operator | type | R obs. | Britton alpha | H alpha | ML alpha | ------------------------------------------------------------------ | -h,-k,l | M | 0.484 | -0.003 | 0.022 | 0.022 | | h,-h-k,-l | M | 0.026 | 0.454 | 0.479 | 0.478 | | -k,-h,-l | M | 0.507 | -0.004 | 0.026 | 0.022 | ------------------------------------------------------------------ Patterson analyses - Largest peak height : 8.386 (corresponding p value : 0.29163) The largest off-origin peak in the Patterson function is 8.39% of the height of the origin peak. No significant pseudotranslation is detected. The results of the L-test indicate that the intensity statistics behave as expected. No twinning is suspected. Even though no twinning is suspected, it might be worthwhile carrying out a refinement using a dedicated twin target anyway, as twinned structures with low twin fractions are difficult to distinguish from non-twinned structures. The correlation between the intensities related by the twin law h,-h-k,-l with an estimated twin fraction of 0.45 % is most likely due to an NCS axis parallel to the twin axis. This can be verified by supplying calculated data as well." Thanks! Lauren