[3dem] ethane-propane mix -summary

William Rice rice at nysbc.org
Wed May 2 16:25:57 PDT 2012

Thanks to everyone for your replies! This seems to be a more interesting 
topic than I expected.

To summarize, it seems several groups do use a mixture of ethane / 
propane without problem. Several blot away excess liquid from the grid 
by touching to a small piece of filter paper under liquid nitrogen 
directly after blotting. Another solution is to not be impatient and 
wait overnight before putting the sample in the microscope. A dull pair 
of forceps may help since they may not wick up as much liquid.

A good idea from Cindi and others is to use pure  or store-bought 
propane and manually mix it with ethane after liquifying. This seems 
better and cheaper than having a specific tank mix. She specifically 
bought  "Worthington Pro Grade" and  "Wagon Master Propane Fuel", but 
apparently there was no special need for high purity.

Other brought up the problems of contaminants  in the gases causing oil 
slicks and blobs on the frozen grids. Also to keep the cryogen cup clean 
of oil contaminants by cleaning or plasma cleaning if available.

William J. Rice, Ph.D.
Senior Scientist
New York Structural Biology Center
89 Convent Avenue, NY, NY 10027

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