Hallo,
there is quite a large number of cryo-protectants other than MPD or
glycerol. If I remember correctly, the Methods of Enzymology, (176) list
some of the, and you might check the recipes of the Hampton cryo screen.
As suggested by Li, you can try oils. You can use small sugars (fructose,
glucose...), PEG400, or 1,6-butanediol (maybe this was 2,5-butanediol) and
mixtures of the above, e.g. 15%PEG400 + 5% glycerol etc.
It also matters how you freeze the crystals - whether you freeze them in
the nitrogen stream at the X-ray machine or dip them into a container with
liquid nitrogen (I prefer the latter)
Also, you can
- dip them directly into the cryo solution
- move them step by step to higher concentrations and hereby observe the
crystals' health under the microscope
- transport the crystals with a pipette rather than using the cryo-loop.
this techniques reduces their exposure to air and exsiccation.
etc. pp
With an inhouse machine you can also try a measurement at room temperature
in a capillary.
Tim
--
Tim Gruene
Institut fuer anorganische Chemie
Tammannstr. 4
D-37077 Goettingen
GPG Key ID = A46BEE1A
On Fri, 24 Apr 2009, Liew Chong Wai wrote:
Hi all,
Good day
I used MPD as a cryoprotectant (20%, 30%) for my crystal. However, there
is no diffraction signal at all. Without the MPD cryo, i still manage to
get 5angstrom, but it has very strong ice-ring signal. I used glycerol
(15%, 20%, 25% and 30%) before, but it cracked the crystal.
Please advice.
Thanks
Liew
