On Mon, Dec 16, 2013 at 1:36 PM, Xiao, Junyu <[email protected]> wrote:
> Dear all, sorry if this topic does not interest you. I wonder whether > anyone has experience with freezing crystals grown in ~0.2 M Magnesium > Formate. Garman and Mitchell suggested that "A major anomaly is solution > 44, 0.2 M magnesium formate, which requires 50% glycerol for > cryoprotection" in their 1996 paper (J Appl. Cryst. 29, 584-587). Since > 50% glycerol is kind of harsh, I wonder whether anyone has tried > alternative cryo protectant. Your kind help will be highly appreciated. > Another good reference: http://journals.iucr.org/j/issues/2002/05/00/do0015/index.html It suggests 35% PEG 400, 30% ethylene glycol, or 30% of whatever "PG" means (based on the rest of the paper I suspect propanediol, but the abbreviation doesn't really make sense - perhaps Eddie Snell can clarify). There are of course many other good cryoprotectants beyond those evaluated in the paper; personally, I'm a big fan of xylitol (which I believe will work in lower concentrations - at least with some conditions), but what really matters is what the crystals can tolerate. Note that these estimates are using very strict criteria - you can often get away with less cryoprotection if you are very good at freezing crystals and/or willing to tolerate some increased background. But I wouldn't try this until you've determined that your crystals can't handle the recommended amounts. -Nat
