Cryogenic vials...really necessary?

David Micklem drm21 at
Thu Oct 9 13:07:21 EST 1997

In article <pxpst2-0810971834020001 at>,
pxpst2 at (Peter) wrote:

>Depends on how long you plan to store them and what you will store them in.  
>The drawback to snap caps is firstly contaimination.  Snap cap seals are
>not 100% airtight.   And with the way they(the snap cap tubes) will be
>opened and closed, one will greatly increase the chance of
>contaimination.  Obviously, if they are bacterial cells and can be grown
>under selection this is not that big of a deal but for eukaryotic cells
>this is a big problem.
>As I said earlier the snap caps are not air tight so exchange of air
>between the inside and outside does occur, and since the outside air is
>very dry(air at -20C does not have the capability of holding moisture in a
>liquid state) the moisture will be drawn out of the tubes.  Remember back
>to general chemistry the princible of sublimation(  WATER(solid)------>
>WATER(gas) skips the liquid pase altogether).  It is what drives the water
>out of the tube and onto the ice sheet in the freezer on the condensor. 
>Since you have glycerol this process will be greatly impeeded due to the
>lowering of the water Vapor pressure.
>Storage time for bacteria in this manner would probably be no more than 9
>months to a year and assuming that you put a secondary seal of parafilm
>around the top.

Hmm.  While this may be true in principle, I suspect that the rate of air
flow between the snap-top tube and the freezer is low enough not to be a
problem.  I certainly have glycerol stocks (at -80, FWIW) that are several
years old but which are still viable (got some out just last week!).  They
have no secondary seal of parafilm either.

Maybe I'm just lucky....


D.R.Micklem,                                Time flies like an arrow... 
Wellcome/CRC Institute,            Fruit flies like a banana.       
Cambridge CB2 1QR, UK               Email:drm21 at
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