Yes, isopropanol is a cryoprotectant, and a relatively good one. So are
the other alcohols. It was even popular in the "olden days" when we
would typically set up drops that were 5-10 microliters in volume
(each!). These take a while (minutes) to evaporate, giving you enough
working time to mount the crystal before the alcohol concentration
changed "too much". Modern nanoliter-scale drops have largely made
alcohol additives impractical, which is a shame.
A potentially general way to deal with evaporating drops is to bathe the
work area in a stream of air or nitrogen that has been pre-saturated
with the reservoir solution. That is, run the gas line in and out of a
jar of say about 50-100 mL of replicated reservoir solution (bubbling
the gas through the solution in the jar) and then route the end of the
hose to under your dissecting microscope and point it at your
crystallization well just before you crack it open. This should give
you a nice, long working time, and similar devices have already been
reported in the literature:
http://dx.doi.org/10.1107/S0021889801020702
That, or you can try to just work really quickly!
-James Holton
MAD Scientist
Chris Meier wrote:
Dear all,
I have a protein which crystallizes in 25% isopropanol, at pH4.5.
Does anyone have experience freezing crystals grown in such a condition?
What cryoprotectants should I try?
Can isopropanol itself act as a cryoprotectant?
Any suggestions on how to deal with isopropanol evaporation during mounting?
Many thanks and best wishes,
Chris
