In case that the poor diffraction quality is a result of problems with
flash cooling directly into liquid nitrogen, it may also be worth trying
to remove the cold gas layer above the liquid nitrogen prior to dipping
the crystal:
Warkentin et al.: "Hyperquenching for protein crystals", J. Appl.
Cryst., Vol. 39, 805-811 (2006)
Good luck,
Dirk.
Savvas Savvides wrote:
Dear Tiancen,
for a survey of post-crystallization options, I highly recommend the following
review article:
Heras B, Martin JL. 2005
Post-crystallization treatments for improving diffraction quality of protein
crystals.
Acta Crystallogr D Biol Crystallogr. 61, 1173-80.
best of luck
Savvas
Quoting Tiancen Hu <[EMAIL PROTECTED]>:
Dear all,
Sorry for the non-CCP4 question. I think this is an old story but our
knowledge to deal with it is very limited. So any suggestions will be greatly
appreciated.
We have crystallized a 21KD protein with 2 disulfide bonds grown for one
month in 0.1M tri-sodium citrate pH 5.6, 0.5M (NH4)2SO4 and 1M Li2SO4. The
crystals look big (~0.4mm x 0.4mm x 0.3mm) and pretty (sharp edge, clean
surface) but diffracted to only 4A in-house. The spots are quite strong and
isotropic at low resolution but decay sharply beyond 5-6A. The crystal
belongs to P4 pointgroup (P422 is also possible) with cell parameters of
127.6, 127.6, 162.5, 90, 90, 90. The solutions we can think of to elevate its
diffraction ability are as follows:
1) Try synchrotron radiation
2) Try a lot of similar crystals and hope one of them diffracts better than
others
3) Let the crystals grow for a longer time and hope it could pack more
¡°orderly¡±
4) Additive screen based on the original condition
5) Check the original plates for other crystallizing conditions
(unfortunately until now this is the only one out of ~300)
6) Screen with other forms of the protein, i.e., N/C-terminus truncated
ones,
complexed with its ligands etc.
I believe many protein crystallographers have encountered similar problems,
are there any successful stories from these fancy poor crystals? Any
suggestions or references will be highly appreciated.
Thanks in advance!
Tiancen Hu
Shanghai Institute of Materia Medica
Rm. 2107, #555, ZuChongzhi Rd.
Shanghai 201203
P.R. China
Tel: +86-21-50806600 ext 2107
Email: [EMAIL PROTECTED]
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Dirk Kostrewa
Paul Scherrer Institut
Biomolecular Research, OFLC/110
CH-5232 Villigen PSI, Switzerland
Phone: +41-56-310-4722
Fax: +41-56-310-5288
E-mail: [EMAIL PROTECTED]
http://sb.web.psi.ch
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