Hello Phenix users.<br><br>I recently solved the structure of my enzyme using SAD to a resolution of 1.9A.  The R values were 0.19/0.25 and the space group was P43212 with a unit cell ~80, 80, 220.  <br><br>I then starting collecting datasets cocrystallized with ATP analogs and noticed that a lot of my datasets have a different unit cell when scaled in P43212.  It comes out to be ~60, 60, 220 and I can NOT get a solution in Phaser with this data.  If I scale it in C2221, then the unit cell is the same (80, 80, 220), but upon refinement, the R factors don&#39;t go much below 0.26/0.32.  Has anyone ever seen something like this happen?  I&#39;m unsure if I should feel like the solution is C2221 since there are space groups of higher symmetry with similar residuals that seem plausible in indexing just the smaller unit cell. Should I keep trying to get a solution out of the data that leads to different unit cell parameters, but has higher symmetry?<br>

<br>Xtriage seems to find twinning, but I think it&#39;s from NCS since my ASU contains a homodimer.  I could also be wrong about this...<br><br>Thanks in advance for any advice!<br><br>*******<br>Leigh Allen<br>Ph.D Candidate<br>

McCafferty Lab<br>Duke University<br>Department of Chemistry<br>