[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [sdpd] Dubious structure
One classic example of a powder structure with vastly higher quality than
a corresponding single crystal structure is C60 at low temperature. The
single crystal structure (Liu et al., Science 254, 408 (1991)) has thermal
ellipsoids that never should have gotten past a reviewer, and should have
told the authors that they have something seriously wrong. Whereas the
neutron powder experiment (David et al., Nature 353, 147 (1991)) has the
complete story of statistical occupancy of two different orientations.
(Note also that the single crystal structure is actually only a refinement
of starting coordinates obtained from -- an earlier powder experiment!)
As for the question of only publishing "pure" structures that do not have
restraints, that would eliminate most macromolecular crystallography even
from single crystals. Modern practice depends heavily on imposing prior
knowledge of the configurations of amino acids, and indeed the protein
sequence of the target protein..
^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~
Peter W. Stephens
Professor, Department of Physics and Astronomy
Stony Brook University
Stony Brook, NY 11794-3800
fax 631-632-8176
[Non-text portions of this message have been removed]
------------------------------------
Yahoo! Groups Links
<*> To visit your group on the web, go to:
http://groups.yahoo.com/group/sdpd/
<*> Your email settings:
Individual Email | Traditional
<*> To change settings online go to:
http://groups.yahoo.com/group/sdpd/join
(Yahoo! ID required)
<*> To change settings via email:
mailto:sdpd-digest...@yahoogroups.com
mailto:sdpd-fullfeatured...@yahoogroups.com
<*> To unsubscribe from this group, send an email to:
sdpd-unsubscribe...@yahoogroups.com
<*> Your use of Yahoo! Groups is subject to:
http://docs.yahoo.com/info/terms/