Cryogenic vials...really necessary?
pgold at MO.NET
Sat Oct 11 11:33:20 EST 1997
> #>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....
> Then so are most other people. The reasoning above is correct, the estimate
> (9-12 mo) is certainly wrong. I just thawed a purified protein sample (stored
> at -80 in eppendorfs in aliquotes of 20 ul) and can attest that they did not
> lost any measurable amount of water during ~ 18 mo.
I've used snap cap tubes for years for bacterial stocks. 11 year old
stocks still no problem.
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