Without seeing your NZ or L-test plots, but looking at the logs, your
data does not appear to be twinned. It will not be R32 because the
R-merge is too high. The probable space group is C2. The listed twin
fractions will approach 0.5 if your data has perfect twinning or you
processed in too low symmetry so the "twin" operator is actually
crystallographic (not a twin operator). The latter is most likely your
case. You may have pseudo-symmetry but without the plots, cannot say for
sure. You probably cannot solve it by MR because your search model may
not be accurate...
Jon
--
Jonathan P. Schuermann, Ph. D.
Beamline Scientist
NE-CAT, Building 436E
Advanced Photon Source (APS)
Argonne National Laboratory
9700 South Cass Avenue
Argonne, IL 60439
email: [email protected]
Tel: (630) 252-0682
Fax: (630) 252-0687
On 04/12/2011 04:27 PM, Teresa De la Mora wrote:
Hello all
I have data that I'm trying to see if it is a pseudo-merohedral twin.
The data process well in C2 or P1 but it does flag R32. I tried to
process in R32 but it didn't work so I processed in both C2 and P1. C2
cell: 104.4 61.6 96.9 90.0 112.9 90.0; P1 cell: 60.7 60.6 95.5 107.1
91.9 118.9. I tried MR in both unit cells looking for 2 mol/ASU in C2
or 4 mol/ASU in P1 and got nothing. I tried Phaser, molrep, epmr and
no solutions was given for any of these programs using both C2 or P1.
I use a complete model as well as a trimmed model (obtained from SMM)
and didn't work either. I used a monomer as well as a combination of
dimers as seen in other published models for this protein, again no
solution. I also ran an SDS-gel of these crystals and it showed the
same MW as the protein I placed for crystallization. So I looked
at back posts from the mail list and I ran phenix.xtriage with C2.mtz
and P1.mtz. Both runs resulted in no pseudo-translation nor -symmetry
found. However, in P1 there is a pseudo-merohedral twin operator: k,
h, -h-k-l and the Britton analysis gives 0.441, H-test gives 0.450 and
ML gives 0.458. This is not shown on C2 analysis. In the P1 analysis
it recommends to process data in C2 so I'm guessing that's why in the
C2 analysis there was no similar twin operator. But it makes me think
that perhaps I don't have a twin crystal since I'm assuming that if it
was twin, it should have been shown on C2 analysis, am I making the
right assumptions? I tried to reprocess the data using the unit cell
recommended in the P1 analysis which is the same as the C2 cell except
that beta=126.76 but it doesn't index well.
This is my first encounter with a possible twin data, could you please
look at the attached logs files and please tell me if I read them
correctly?
And if it is not twin, not pseudo-translated nor -symmetry, what other
things could be hindering the structure solving?
Thank you for your kind suggestions/answers.
Teresa
Teresa De la Mora-Rey Ph.D.
Dept. Medicinal Chemistry
University of Minnesota
8-101 Weaver-Densford Hall
308 Harvard St. SE, Minneapolis, MN 55455
Lab phone (612) 626-5226
"If you never did you should. These things are fun and fun is good"
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