Can you send the exact unit cell parameters? The number you give now
are to rough to make a fair comparison.
In any case, C2221 does lie directly below P43212 (see attached
figure), so you have a good chance that is a possibility.
On the other hand, so are P43 and P212121.
It is fairly straightforwadr to try all, just cumbersome.
I suggest however you get your data in P1, and solve it in that spacegroup.
Subsequently, run
phenix.xtriage p1data.mtz reference.structure.file=MR.1.pdb
and start interpreting the RvsR tables.
Contact me directly if you have difficulties with this, or share with
the bb as this is a very instructive exercise.
Cheers
Peter
2009/8/25 Leigh Allen
Hello Phenix users.
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.
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't go much below 0.26/0.32. Has anyone ever seen something like this happen? I'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?
Xtriage seems to find twinning, but I think it's from NCS since my ASU contains a homodimer. I could also be wrong about this...
Thanks in advance for any advice!
******* Leigh Allen Ph.D Candidate McCafferty Lab Duke University Department of Chemistry
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