Hi,
I have cOmplete™ Protease Inhibitor Cocktail tablets with expiration date September 2019. At this moment they are stored at +4°C, according to data sheet. I would like to prolong shelf life after expiration date so I am considering dissolving them, aliquoting and freezing. Stock solution (25x) is stabile for at least 12 weeks at -15°C to -25°C. I found that some components of cocktail are unstable in aqueous solutions so I am wondering is it better to freeze tablets or stock and at -20 °C or -80°C?
If you are worried about the stability of the tablets at 4 °C, why don't you store them dry at -20 or -80 °C ? A) it will occupy less space in your refrigerator than the solutions; B) whatever the conditions, serine protease inhibitors like PMSF will hydrolyse in the presence of water
dissolving them will shorten the expiration.
Pierre's advice is good. However, I would not choose -20C, as you have proteins in your mix; -80C is better.
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