If I would like to freeze a protein supernatant for later testing with ELISA. Is this possible? Would the de-freezing damage the proteins? What are the ideal conditions/protocol?
Hello
You can freeze a protein supernatant at - 20 degree C for later testing with ELISA. For long-term storage you can freeze the protein supernatant
at -80 degree C.
Repeated freeze-thaw cycles could damage the proteins. So, I would suggest you prepare aliquots of protein supernatant for one time use in order to avoid repeated freeze-thaw cycles.
Best.
Definitely yes. You must first aliquot the protein and preserve it at -20 for relatively less time (a year) or @-80 for longer storage.
I have used fish serum for antibody assays, if you dont do repeated thawing and freezing, it is reasonably stable in producing ELISA results for even 6 months. If you can precipitate, dialyze and freeze dry..its good as you can store it in normal fridge for long.
Yes you can freeze a protein. With antifreeze solution, there is no problem. Without that, there will be slow denaturation and loss of quality. Ensure that the temperature of your freezer do not fluctuate. It is a general thinking that
fluctuations of around 2 degree do not damage proteins but in fact they do. The minor heat input would result in melting and refreezing of few micro ice crystals. Fluctuations will be akin to what Dr Azad wrote as freezing and thawing. This is more prominent in -20 and one may not have a problem in -80. Have a stable deep freeze if you are planning for long term storage at -20. Usually freezers with less than 0.5degree Celsius variation are very good. For long term storage, avoid a freezer that is too often opened . Choices are subject to availability, but this knowledge can be helpful in protecting your stuff.
Freezing at - 20 degree C and thawing once may not cause appreciable structural damage. But freezing at -80 degree C and thawing may cause some problems. Because protein folding can be affected. So better to avoid repetition.
Just as Binaya Bhusan Nayak said ensure to keep at -20 without temperature fluctuations since this might cause denaturation or folding and hence antibody contact might be restricted during ELISA. I wouldn't advice longer preservation at -80 either.
You can freeze it in -20 for short periods and in -80 (deep freezer) for long periods but try to avoid repeated freezing and thawing cycles which will affect protein structure..
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