Another example of a structure with intervening
layers of weak electron density at 1.75 A
resolution is Pb2+ bound calmodulin that Mark Wilson
solved in my laboratory: M.A. Wilson and A.T. Brunger, /
Acta Cryst./D59, 1782-1792 (2003), PDB ID 1NOY.
The intervening layers are not entirely disordered since
PB2+ positions show up in difference maps in these
layers, so it could indicate motion around these positions rather than
complete disorder. However, apart from the Pb2+ positions,
the electron density in these layers is weak and un-interpretable.
Apart from the weak layers, the structure behaves completely
normal, i.e., we observe the expected bulk solvent contribution
at low resolution, and the B-factor distributions are as expected.
Axel
Petr Leiman wrote:
----- Original Message ----- From: "Jenny Martin"
<[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Thursday, August 23, 2007 5:46 PM
Subject: Re: [ccp4bb] The importance of USING our validation tools
My question is, how could crystals with 80% or more solvent diffract
so well? The best of the three is 1.9A resolution with I/sigI 48
(top shell 2.5). My experience is that such crystals diffract very
weakly.
You must be thinking about Mark van Raaij's T4 short tail fibre
structures. Yes, the disorder in those crystals is extreme. There are
~100-150 A thick disordered layers between the ~200 A thick layers of
ordered structure. The diffraction pattern does not show any anomalies
(as far as I can remember from 6 years ago). The spots are round,
there are virtually no spots not covered by predictions, and the
crystals diffract to 1.5A resolution. The disordered layers are
perpendicular to the threefold axis of the crystal. The molecule is a
trimer and sits on the threefold axis. It appears that the ordered
layers somehow know how to position themselves across the disordered
layers. I agree here with Michael Rossmann that in these crystals the
ordered layers are held together by faith.
Mark integrated the dataset in lower space groups, but the disordered
stuff was not visible anyway. He will probably add more to the
discussion.
Petr
Any thoughts?
Cheers,
Jenny
--
Axel T. Brunger
Investigator, Howard Hughes Medical Institute
Professor of Molecular and Cellular Physiology
Stanford University
Web: http://atb.slac.stanford.edu
Email: [EMAIL PROTECTED]
Phone: +1 650-736-1031
Fax: +1 650-745-1463
