Dear Israel,
as Martin pointed out we have a device here at the ESRF/EMBL, the
HC1b, that produces a stream of air with a precisely controlled RH at
the sample position that we have used with some success to monitor the
effects dehydration has on diffraction quality. The same device is also
available at Diamond, Max-Lab and, I believe, BESSY. The example you
describe is a classic example of the sort of system that will usually
benefit from controlled dehydration. Depending on the size and
concentration of the LMW PEG you are using you have probably reduced the
"RH" surrounding your crystal by ~10%. The best thing to do now is
repeat these experiments using the HC1b to really define the changes in
the lattice of your crystals and find the optimum dehydration conditions
for your crystals. At the ESRF the device can be requested for any
experimental session (just click the check box on the A form) and I
presume that this will be similar at the other synchrotrons.
As well as the reference describing the device we have recently
published a further description of typical experimental conditions and
some successful applications:
http://dx.doi.org/10.1016/j.jsb.2011.03.002
And the ESRF webpage is here:
http://www.esrf.fr/UsersAndScience/Experiments/MX/About_our_beamlines/ID14-2/HC1b
Good luck! Matt
On 01/05/2011 19:32, Israel Sanchez wrote:
Hi folks,
I am currently impressed by the efficiency of dehydration treatments
over the diffraction capacity of our crystals in one particular
condition. Without any treatment the crystals seldom diffract to
20-30A but in our last synchrotron trip the very same crystals, after
been incubated with increasing concentration of low molecular weight
PEGs diffracted to 6A.
I was wondering if anyone has studied these effects in a systematic
way. Does anyone on the ccp4bb knows references or has any
experience/pseudo-religious believes that do not care to share with
the community about this particular topic?
Thank you very much in advance!!!!
--
Israel Sanchez Fernandez PhD
Ramakrishnan-lab
MRC Laboratory of Molecular Biology,
Hills Road, Cambridge, CB2 0QH, UK
--
Matthew Bowler
Structural Biology Group
European Synchrotron Radiation Facility
B.P. 220, 6 rue Jules Horowitz
F-38043 GRENOBLE CEDEX
FRANCE
===================================================
Tel: +33 (0) 4.76.88.29.28
Fax: +33 (0) 4.76.88.29.04
http://go.esrf.eu/MX
http://go.esrf.eu/Bowler
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