5 upvotes, 1 direct replies (showing 1)
View submission: Ask Anything Wednesday - Biology, Chemistry, Neuroscience, Medicine, Psychology
Why do certain biological samples (plasma, embryos, etc.) have to be stored at temperatures that are far below freezing as opposed to just simply frozen? What's happening at -30 C that's not happening at minus -5 Celsius or vise versa?
Comment by aTacoParty at 17/01/2024 at 17:52 UTC
6 upvotes, 2 direct replies
Freezing slows biological processes but does not stop them. Sample degradation will continue happening at low temperatures just much slower. DNA is more stable than protein or RNA so it's often kept at -20C. Protein and RNA are often kept at -80C. Live cells are often kept at -180C.
In an ideal world everything would be kept at ultra low temperatures, but the lower the temperature, the more it costs to store. To get -180C requires liquid nitrogen which is a lot more expensive than running a compressor (IEA for -20 and -80 freezers)
Another benefit of storing samples at low temperatures is that fluctuations in temperature won't cause accidental thaws. If samples were kept at -5C, then opening the door might cause the temp to jump up past 0C causing a thaw then a refreeze which degrades samples much faster.