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Hi,
My question concerns the refinement of two complete alternate
structures in a protein crystal using a medium/low resolution dataset
(2.7 - 3 Å).
The problem is the following : an enzymatic process was triggered in-
crystallo by means of a laser, inducing a 0.5 Å loss in the
diffraction limit with respect to that of a crystal not exposed to
the laser beam (un-exposed). The model obtained fits the electron
density quite well, though Rfree values do not get lower than 32%.
Hence, I generated two complete alternate structures, starting with
that which was refined from the unexposed crystal; the first
conformation (50%) was kept rigid while the other one (50%) was
subjected to simulated annealing.. The Rfree decreased by 0.5%.
Since quite large differences are observed between the two alternate
structures, I am now wandering if what I observe is indeed true (ie
related to the enzymatic process triggered by virtue of the laser) or
if it could be artefactual and due to the low resolution of the data
set ?
Does anyone have an idea about this??
Thanks in advance,
Jacques-Philippe Colletier
Ph. D. Student
Molecular Biophysics Laboratory
Institute of Structural Biology
41, rue Jules Horowitz
38027 Grenoble Cedex
tel : +33.4.38.78.96.28
fax : +33.4.38.78.54.94
mailto : [EMAIL PROTECTED]
