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Hi Michelle,
Better throw away all images, end up with no data to guarantee an
R-merge of 0 and try homology modeling approaches.
Now a more serious advice, If you get a good solution in P3121 and you
have an indication that the data is twinned, I guess you stick with that
space group. The table below shows the statistics from space group
P3121 or the space group P6222? I wouldn't be worried out Rmerges, as
long as your I/sigI looks reasonable. Can you say something about
redundancies?
2.6 A data might be a bit on the edge for Shelxl, I guess that others
can give better advice there. CNS does a good job as well for twinned data.
HTH
Peter
Michele Lunelli wrote:
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Dear all,
After integrating and scaling a dataset using Denzo and Scalepack, I
obtained the following results:
Shell Lower Upper Average Average Norm. Linear Square
limit Angstrom I error stat. Chi**2 R-fac R-fac
50.00 5.60 524.2 11.4 6.8 1.080 0.045 0.041
5.60 4.45 319.3 13.0 7.5 1.108 0.091 0.103
4.45 3.88 301.0 17.8 8.7 0.989 0.114 0.123
3.88 3.53 187.9 12.7 9.1 1.027 0.141 0.148
3.53 3.28 103.2 9.2 8.6 1.068 0.201 0.193
3.28 3.08 66.7 8.6 8.5 1.054 0.304 0.299
3.08 2.93 44.6 8.6 8.6 1.010 0.480 0.472
2.93 2.80 32.8 8.6 8.6 1.009 0.648 0.645
2.80 2.69 25.3 8.5 8.5 0.982 0.844 0.689
2.69 2.60 16.6 8.3 8.2 0.957 0.000 0.990
All reflections 168.1 10.7 8.3 1.030 0.129 0.083
The I/sigma is 2 at the resolution 2.6 A, but the Rmerge for the high
resolution shells is very high, actually higher than 1 for the last
shell! My question is: should I keep all the data, or should I cut them
around 3.1 A in order to have a resonable Rmerge even for the last shell?
I should say that the data appear to be twinned (based on the tests of
truncate, the Yeates twinning server, and Dataman with the
Yeates-Padilla method) with a twinning fraction around 0.46. The
apparent space group is P6222, but I obtained a good MR solution in P3121.
If I can I will refine the structure with Shelxl, but therefore it is
important to have at least medium resolution data.
Thank you in advance,
Michele Lunelli
Department of Cellular Microbiology
Max Planck Institute for Infection Biology
Campus Charité Mitte
Charitéplatz 1
D-10117 Berlin
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