Storage of 2-ketoglutarate - Help please (Dec/10/2006 )
I am frequently using 2-ketoglutarate (or 2-oxoglutarate). The thing is that i use quite small amounts every time ( i am using it as a cofactor for a transcription factor) and i have to bring it to pH of about 8. The preparation procedure involves titration and measuring and therefore i have to make about 10 ml every time. It takes quite a while (especially the titration part) and i would like to save this time.
I am interested to know whether someone is using 2OG at similar pH and whether they know if it could be stored for longer periods and at what conditions.
I have already consulted catalogs and manuals of different companies (ex. Sigma Aldrich) and they only give storage conditions for dry powder.
Thanks in advance
Make up a 120ml and store in aliquots of 12ml in a -20 or -80Deg freezer. One freeze-thaw cycle should be ok. I would also give "lot numbers" to your solutions so that you can track their performance. When you get to the last vial or so plot performance of the entire lot against time. Until you "proove" this system, I'd thaw the material then confirm the titration.
Alternative to making up and storing 2OG at the conc you use it at, you could make up concentrated vials (say 10X) that you dilute in suitable buffer. That way you are storing smaller volumes (1.2ml?) so taking up less room in the freezer. Again, keep lots numbers and do a performance plot.
If you get bacterial growth try adding azide, though this doen't work so well at alkaline pH.
if i remember correctly, we used to freeze 2-ketoglutarate and it handled multiple freeze-thaw cycles, but that was a long time ago so i am not sure.
to be safe, you can aliquot and freeze yours in single use volumes (with some excess for pipetting error) and only thaw once.
thank you very much, that is the answer i was hoping for...
any idea whether pH will affect the number of freeze-thaw cycles ?
That's why you should confirm the titration in the preparative step.
probably only as much as the pH affects the stability of the compound in solution.
great help guys, thank you very much!