Hi everyone, I have a data set to 2.8A, with most likely 2 molecules in the asu and a molecular replacement model with 40% sequence identity. (Cell 71.3 71.3 227.9 90 90 90) Initially the data appeared to be either P4322 or P43212 (Rsym = 7.4%; Cell 71.3 71.3 227.9 90 90 90), but the molecular replacement solutions had major clashes with the symmetry related molecules and a lower LLG for the solution of the second molecule. No twinning was detected by Xtriage. Processing the data in P212121 (Rsym 5.6%, cell 71.3 71.4 228.2 90 90 90) gave me a better molecular replacement solution (LLG 121/373), but I had 5 clashes with the second molecule in the asu. (I tested all alternative spacegroups) I also have a MAD dataset (very low quality!) and I combined the phases with the one obtained from molecular replacement in Sharp. After NCS averaging the maps had improved (still not great). I tried to improve things in the model and run Phaser again and the solution had better statistics (LLG 338/1223) and the clashes were reduced to 2. Xtriage detected pseudo-merohedral twinning with a twin fraction of 43% with twin operator -k, -h, -l. So I tried refining the model with phenix telling it the twinning operator and fraction, but R/Rfree are stuck around 45%. I also tried simulated annealing but that gave even higher R/Rfree. Is there anything I can do, or is it a hopeless case? Thanks for your help in advance! Sabine This message has been checked for viruses but the contents of an attachment may still contain software viruses, which could damage your computer system: you are advised to perform your own checks. Email communications with the University of Nottingham may be monitored as permitted by UK legislation.