Dear Tiancen,
I would suggest to try optimizing the hydration state of the crystal.
Either with a humidity controller (e.g. FMS system) at room temperature (or
4 degrees), with which you can optimize the diffraction,
or by partially drying the crystal on a filter paper soaked with some
precipitant or mother liquor before freezing it
(with or without cryo-protectant). Alternatively, it is worth trying to
partially dehydrate the crystal by transfering it into a buffer with higher
salt/precipitant concentration (see for example the elegant soaking
procedure described in P. Cramer et al., Science 2000).
Good luck!
Bruno
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]
############################################################################
Dr. Bruno P. Klaholz
Department of Structural Biology and Genomics
Institute of Genetics and of Molecular and Cellular Biology
IGBMC - UMR 7104
1, rue Laurent Fries
BP 10142
67404 ILLKIRCH CEDEX
FRANCE
Tel. from abroad: 0033.390.24.47.98
Tel. inside France: 03.90.24.47.98
Fax from abroad: 0033.388.65.32.76
Fax inside France: 03.88.65.32.76
e-mail: [EMAIL PROTECTED]
websites: http://igbmc.fr/Klaholz http://www-igbmc.u-strasbg.fr/
