Herman,
The trick you suggest is not as valid as you may think. The ice rings can
originate from the crystal itself.
If you crystallize in a high concentration PEG precipitant you will avoid
ice rings,
but if you transfer or soak your crystals in the same solution the high
molecular weight
PEG will not enter the crystal lattice and you will still get ice rings.
I have a picture of this in:
Vera, L., Stura, E. A. (2013) Strategies for protein cryocrystallography.
Crystal Growth & Design, e-print
http://pubs.acs.org/doi/full/10.1021/cg301531f PDF: Figure3 Page G.
So cryoprotectants need to penetrate the crystal lattice to prevent ice
rings, but even in the
presence of ice rings the data can be used.
Regarding optimization:
The main problem you encounter in cryoprotection is that some compounds
like glycerol and ethylene glycol solubilize protein crystals, but if you
create a
mixture of various compounds that is precipitation-solubilization neutral,
then
there is no real need for optimization.
Enrico.
On Tue, 27 Aug 2013 08:30:28 +0200, <herman.schreu...@sanofi.com> wrote:
A trick I like is just to freeze the reservoir solution or would-be
cryo-solution without a crystal present. If the frozen solution stays
clear and does not show ice rings on e.g. a home source, it is worth
trying. Otherwise, the solution needs optimization.
Herman
-----Ursprüngliche Nachricht-----
Von: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] Im Auftrag von
Uday Kumar
Gesendet: Freitag, 23. August 2013 19:52
An: CCP4BB@JISCMAIL.AC.UK
Betreff: [ccp4bb] cryoprotection
Hello
Can anyone suggest a cryoprotectant for the following crystallization
condition
0.2-0.4M sodium formate
~20% PEG 3350
0-25 mM Nickel
0-100 mM Malonate
Thank you
with regards
uday
--
Enrico A. Stura D.Phil. (Oxon) , Tel: 33 (0)1 69 08 4302 Office
Room 19, Bat.152, Tel: 33 (0)1 69 08 9449 Lab
http://www-dsv.cea.fr/ibitecs/simopro/ltmb/cristallogenese
LTMB, SIMOPRO, IBiTec-S, CE Saclay, 91191 Gif-sur-Yvette, FRANCE
http://scholar.google.com/citations?hl=en&user=Kvm06WIoPAsC&pagesize=100&sortby=pubdate
http://www.chem.gla.ac.uk/protein/mirror/stura/index2.html
e-mail: est...@cea.fr Fax: 33 (0)1 69 08 90 71
