[phenixbb] pseudo-translational symmetry refinement
a a
oldclifford at yahoo.com
Tue Apr 29 14:08:23 PDT 2008
Dear all:
We have a set of crystal data having psuedo-translational symmetry when examined with xtriage:
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Twinning and intensity statistics summary (acentric data):
Statistics independent of twin laws
- <I^2>/<I>^2 : 2.519
- <F>^2/<F^2> : 0.724
- <|E^2-1|> : 0.854
- <|L|>, <L^2>: 0.504, 0.337
Multivariate Z score L-test: 1.854
The multivariate Z score is a quality measure of the given
spread in intensities. Good to reasonable data are expected
to have a Z score lower than 3.5.
Large values can indicate twinning, but small values do not
necessarily exclude it.
No (pseudo)merohedral twin laws were found.
Patterson analyses
- Largest peak height : 67.742
(corresponding p value : 4.897e-06)
The analyses of the Patterson function reveals a significant off-origin
peak that is 67.74 % of the origin peak, indicating pseudo translational symmetry.
The chance of finding a peak of this or larger height by random in a
structure without pseudo translational symmetry is equal to the 4.8972e-06.
The detected tranlational NCS is most likely also responsible for the elevated intensity ratio.
See the relevant section of the logfile for more details.
The results of the L-test indicate that the intensity statistics
behave as expected. No twinning is suspected.
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The structure was solved by auto-sad at 2.7A. However, the r-factor can not be lowered by phenix.refine (TLS+ADP+rigid). Is there any manipuliations we can do to deal with this situation?
Thanks,
Zhiyong Ren,
MD Anderson Cancer Center
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