[phenixbb] P43212 spacegroup change to C2221?

Peter Zwart phzwart at gmail.com
Tue Aug 25 10:47:44 PDT 2009

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.



2009/8/25 Leigh Allen <c.leigh.allen at gmail.com>:
> 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
> _______________________________________________
> phenixbb mailing list
> phenixbb at phenix-online.org
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P.H. Zwart
Beamline Scientist
Berkeley Center for Structural Biology
Lawrence Berkeley National Laboratories
1 Cyclotron Road, Berkeley, CA-94703, USA
Cell: 510 289 9246
BCSB:     http://bcsb.als.lbl.gov
PHENIX: http://www.phenix-online.org
CCTBX:  http://cctbx.sf.net
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