Dear Murugan,
at higher resolution, the Wilson plot captures mainly the contribution
of atoms with lower B-factors which leads to a systematic
underestimation of the true B-factor distribution. Accordingly, the
average B-factor of refined structures tend to be higher then the Wilson
B-factor, at least in my experience. In your case, it is the other way
around. One possible problem could be, apart from the fit of the Wilson
plot as James Holton suggested, that you have reflections at very low
resolution with underestimated intensities due to cut overloads or
measurement in the half-shadow of the beamstop. This would result in a
too low overall B-factor for the model in order to try to fit the
usually stronger low resolution reflections at the cost of the weaker
high resolution data. One quick check of this hypothesis is to cut the
low resolution at, say, 10 A instead of 50 A and run a test-refinement.
If this results in more realistic model B-factors, you should have a
closer look at the low resolution data and exclude the ill-measured ones.
Best regards,
Dirk.
Am 30.06.10 19:31, schrieb Vandu Murugan:
Dear all,
If one could find a difference of more than 15 between Wilson B
factor of the data ( 55) and Mean B factor of the structure, (30) what
could be the possible reasons? I am seeing it in my structure. Could
someone tell me why it could be?? Thanks in advance.
Yours faithfully,
Murugan
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Dirk Kostrewa
Gene Center Munich, A5.07
Department of Biochemistry
Ludwig-Maximilians-Universität München
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D-81377 Munich
Germany
Phone: +49-89-2180-76845
Fax: +49-89-2180-76999
E-mail: kostr...@genzentrum.lmu.de
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