Greetings,
Does anyone have information about the shelf life of the following cocktails"
- Protease Inhibitor Cocktail Set-III (Calbiochem)
- Phosphatase inhibitor cocktails Set-II (Calbiochem)
There is no technical information on the label. Technical service department has no clue but saying we don't guarantee beyond one (1) year from the delivery.
Also, if you have a simple assay to test whether these inhibitor cocktails are still good,
please kindly share your experiences with us.
Kind regards
Baki
Its very hard to test all the multiple components as they are directed to many distinct classes of proteases. If the Set II hasn't been reconstituted and is dry I'd probably trust it more than the Set III which is shipped in a DMSO solution. The one very labile component is the AEBSF which hydrolyzes quickly. You might be able to get near full functionality by adding some fresh AEBSF or PMSF to either cocktail, but the only way to be sure is a time machine (or buy again!) good luck!
Thanks Edward for your input. The vials were frozen when we purchased and we are really using very little amount per assay. So, the stock solution is being repeatedly undergo freeze-thaw cycle.
Well freeze/thaw cycling is exactly what the Mfg. warns against. I'd suggest single use aliquoting into tiny PCR tubes after resuspension in the driest DMSO possible at -20C (ideally -80C). Sigma used to sell a DMSO stored over 3A or 4A molecular sieves, and its the AEBSF thats most labile to hydrolysis. Many of these components can be bought in pure form (GoldBio is cheap) brough up in dry DMSO and then carefully aliquoted for single use, its the tablets and premade mixes that are very expensive. Good luck!
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