Hi all, my lab currently uses thermofisher's Pierce protease and phosphatase inhibitor mini tablet. I noticed that the expiry date was back in May 2020. I keep the tablets at 4°C, and dissolve 1 tablet in 10ml of RIPA lysis buffer, and store those in -20°C after aliquoting them into 1ml eppendorf tubes. However, I frequently freeze-thaw those 1ml eppendorf tubes as my experiments only require a small amount of RIPA buffer each time. Will the phosphatase inhibition still work after the tablet's expiry date?
It will probably still work, though perhaps not as well as in-date tablets. If you see issues with your downstream analyses, you should definitely consider purchasing new inhibitors as part of your troublshooting.
It will probably work, but will loose efficacy over time, also the freeze thawing is not helping either. I would make those 1mL aliquots expendable, once thawed it is trash. In my experience, I don't want to chance the results of the experiments at a critical timepoint due to questionable protein storage. Best to use fresh so as to avoid spending time guessing/ troubleshooting random questionable results. Justifying saving a few dollars, which may be a fraction of what the total cost of the experiment, is not worth the time and effort correcting the problem.
I think it is working, but not at the same efficiency as if it is within its working date.
In general, if you run a control under the same condition. As far as you are not setting reference values to be used by others it should be ok to be used.
Remind you that it is advised to keep the biochemicals as a powder rather than, as a solution to keep them stable, and often most chemicals keep their activities for at least 6 months after the written expire date.
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