Dear all, I have set of data (~2.7A). After indexing, HKL2000 suggests a rhombohedral space group or C centered monoclinic space group. I tried molecular replacement with R32 ( 109.55 109.55 155.28 90.00 90.00 120.00) and C2 (121.092 109.315 81.537 90.000 97.874 90.000) (both have good merging statistics), but did not get any solution. I also tried P1 ( 81.553 81.527 81.523 84.202 84.132 84.156) but did get any solution ( wt structure is known and the only difference with the wt structure is that the new structure is complexed with a smaller protein). I expect that there'll be some domain movement so searched for individual domains in phaser.
The self rotation function in P1 showed both two fold and three fold peaks but they were both off the centre. The data does not appear to be twinned. I am curious to know if it is normal for cell dimensions to drastically vary from one space group to another. I am running out of ideas, could I be dealing with a wrong space group or pseudosymetry? Any suggestions would be appreciated. Thanks. Josiah.