On 20 Aug 2008, at 8:11, Wim Burmeister wrote:
James Pauff a écrit :
Hello all,
I have a refined structure at 2.6 angstroms that at about 73%
completeness at this resolution. The I/sigma is about 2.0 at 2.6
angstroms, and the omit density for my ligands is great contoured
at 3.0sigma. My Rcryst is 19 or so and the Rfree is 24.5 or so.
HOWEVER, my mean B value is 13.9, whereas my other 2 structures
(at 2.2 and 2.3 angstroms, same protein, >95% completeness) have
mean B values of 22+. Any suggestions as to what is going on
here? I'm having trouble explaining this.
Thank you,
Jim
Dear Jim,
probably you did not collect your data to the highest possible
resolution. Did you use an inhouse source? You would expect that a
crystal with an average temperature factor of 14 A2 would diffract
to 1.6 A on a synchrotron source.
Regards
Wim
Indeed.
I could also speculate that if the completeness is 75% because 25%
of the *weakest* reflections are missing that would artificially show
a lower B factor. Did you look at the actual Wilson B plot - if not
do, you can learn a lot of simple things from this graph (its there
in the Truncate output, usually part of a scaling run, after SCALA)
A.
--
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Wim Burmeister
Professeur, Membre de l'Institut Universitaire de France
Unit of Virus Host Cell Interactions (UVHCI) UMR5233 UJF-EMBL-CNRS
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B.P. 181, F-38042 Grenoble Cedex 9 FRANCE
E-mail: [EMAIL PROTECTED]
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