Hi everyone,
I have got a dataset to 2.8A which according to Mosflm/XDS have P4 (etc) or P222 (etc) symmetry with a=b=71 c = 228 (same penalty in both programs). According to Matthews coefficient and self-rotation function (GLRF and Molrep at kappa=180) I have 2 molecules in ASU, related through NCS. Looking at systematic absences in hklview it seem to be P4. I initially processed the data in P4 and pointless suggested P41 21 2/P43 21 2, so I reprocessed the data in P41 21 2. As a molecular replacement model I used an ensemble of 3 structures each with (unfortunately) only ~20% sequence ID and search was carried out with one molecule. Residues that in the search model that were not identical were stripped back to C gamma by chainsaw and the B-factors were reset to 10 (mc) and 20 (sc). I run Phaser searching in all alternative space groups and 2 molecules in the ASU and it found a solution in P43 21 2. When I input the data again in P43 21 2 into Phaser searching all spacegroups I get a solution in P43 2 2? The difference in the two solutions is association of the two molecules in the asymmetric unit along b. I reprocessed the data in P43 2 2 and run phaser again against all space groups and am finding P43 21 2? I thought I might have mistaken the NCS as crystallographic symmetry and have processed them in a to high symmetry space group. The data are merging OK in P222 (Rmerge 5.3%) and P4322/P43212 (6%/6.5%). I run Phaser with the data processed in P 2 2 2 against all possible space groups and it found a solution in P2 2 21. In all solutions (orthorhombic and tetragonal) I have clashes with the symmetry molecules looking at the results in Coot. The rotation function Z-scores and translation function Z-scores are low as expected with 2.7 -2.9 and 4.7-5, respectively. And of course the maps from Phaser are rather poor, but there are bits and pieces which seem to make sense and I was hoping that I could at least determine the space group. Any comments are much appreciated! 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.
