Cryogenic vials...really necessary?
klenchin at facstaff.REMOVE_TO_REPLY.wisc.edu
Thu Oct 9 20:06:39 EST 1997
In article <drm21-ya023080000910971807210001 at nntp-serv.cam.ac.uk>, drm21 at mole.bio.cam.ac.uk (David Micklem) wrote:
#In article <pxpst2-0810971834020001 at pelli.pathology.pitt.edu>,
#pxpst2 at vms.cis.pitt.delet.edu (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....
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.
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