I would like to measure the protein concentrations of the lysates I prepared for the Western blot method at the same time. How long can I wait for these lysates to remain stable?
Generally, your lysates should stay stable at -20C for a few weeks to at least a few months. However, freeze-thawing can lower the stability of a number of proteins, and could affect your overall concentration. For your case, since your samples are undergoing just one freeze thaw prior to western blotting, you should be fine unless its a very delicate protein. I would recommend all of your samples go through one freeze thaw instead of blotting some fresh ones and some thawed ones so that you do not get variability in concentration that is skewed by the freeze thaw. It is hard to say whether or not your concentration of soluble protein will change after the freeze thaw without knowing more details about your protein.
Best,
Max
Hi, you can aliquot your proteins prior to storage at -20degreesC, so that to reduce the free-thaw cycle. Generally, proteins should be stable under -20degreesC for 6 months. We have also tried to keep the proteins in ice (not-frozen, but you would need to replace the ice now and then) and it remained stable for at least 1 month. I found this method more reliable in terms of stability. However, do remember to supply sufficient protease inhibitor upon cell lysis to prevent protein degradation. Best of luck!
I think is better to aliquot sample after homogenization in ORDER to have same concentration. In that way you can quantify without freezing an thawing the totallity of the sample
I agree, proteins (including its concentration) should be stable at -20°C.
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