[3dem] Ethane - propane mix

[Cindi Schwartz]

Bill,

We use both routinely. On our manual plunger, it's pure ethane and it seems to work fine (although we routinely freeze the day before we are on the scope--it's very uncommon for us to freeze right before putting the sample in the scope).

We use a ethane/propane mix (60,40) in the vitrobot. In fact, it's high purity ethane and propane we bought at the hardware store that was sitting around in the lab for years. We don't have any contamination issues (mentioned by Bob) and it seems to work fine (meaning consistently vitreous). We also just mix it by eye--usually putting in the propane first and then swirling the ethane in there so it's good and mixed.  

I don't know if that helps, but I guess the reason we don't go direct is b/c with ethane-only freezing, we would crash the vacuum too often so it's become lab protocol to store overnight and then do microscopy.

Hope it helps,
Cindi

On May 1, 2012, at 2:02 PM, William Rice wrote:

> Dear all,
> 
> Have many of you had experience using a mix of 37% ethane / 63% propane as a cryogen? It has the advantage that it stays liquid at liquid nitrogen temperature. We had thought it would be easier to handle, but we found that it seems to leave a thin layer of liquid cryogen on the surface of the grid. Putting a freshly frozen grid into the microscope seemed to cause problems with the IGP as this liquid seemed to evaporate only in the high vacuum of the microscope. Solid ethane frozen on the grid usually cracks and breaks off or sublimes in the airlock during pumping before insertion. Has anyone else seen this effect?
> 
> Thanks,
> Bill
> 
> -- 
> William J. Rice, Ph.D.
> Senior Scientist
> New York Structural Biology Center
> 89 Convent Avenue, NY, NY 10027
> 
> 
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Cindi L. Schwartz
University of Colorado
Dept. MCDB
347 UCB
Boulder, CO  80309
O: 303-492-7980
F: 303-735-0770
http://bio3d.colorado.edu
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