Are your proteins degrading in the freezer?

Protein freezing and stability

Whenever we want to keep our protein samples safe, we freeze them. It sounds like a very simple and safe thing to do, but how do we know that our proteins remain stable and functional while frozen or after being thawed?

A common mistake among scientists is relying on faith that proteins are unaffected by storage conditions. But the fact is, freezing, long-term storage and even freeze-thaw cycles can cause loss of functional properties and conformational changes of proteins. For example, did you know that during freezing — and particularly during slow freezing — the growth of ice crystals excludes salts and ions and pushes them into the non-frozen region? This phenomena — known as freeze concentration  can cause high salt or protein concentrations in the aqueous phase, causing severe stress to protein stability.

However, stability is an inherent property of a protein, meaning that not all proteins behave in the same way under the same storage conditions.

While a protein can tolerate freezing and thawing through many cycles, others can easily be denatured while freezing for the very first time. This is why it’s the researcher’s responsibility to check the quality of a protein sample after every freeze-thaw cycle. This routine check may also be used to test different storage conditions to determine which performs best for a particular protein.

If you want to know more on how to check your protein’s quality after taking it out from the freezer, take a look at this application note.