retionic acid stability in MEM at 4C

[mcbenus]

Hi, I am using retionic acid to differentiate SH-SY5Y cells. My stock solution at DMSO is stored at -80C, and I made about 50ml of retionic acid at 10uM in cell media for daily usage.

Does anybody know how long can I use these 50ml? It is usually at dark (refrigerator). Is it better to freeze it (but then have freeze-thaw cycles)? Do I better make new retionic acid from stock every time I treat the cells? Does the stock go bad from freeze-thaw cycles?

I'd appreciate any inputs. Thanks!

[JackBean]

Why don't you freeze it in aliquots?

[mcbenus]

Thanks for the suggestion. That is possible of course, but is just more work. I will have to make aliquot for each day I am treating the cells with RA. Since I am planning a few weeks of experiments it becomes a lot of pipetting, dilutions, etc. I will do it if I realize I need to, just wanted to see if I can use the same aliquot for a week, for example.

[JackBean]

Why many pipetting? How much from the 50 ml stock do you use per day? Just take this volume, round it up, and freeze. Than you will take one aliquot per day and the rest will be the same as if had it in one tube

[mcbenus]

Thanks for the answers, that's what I'll do. do you know maybe how freeze-thaw cycles of DMSO stocks effect retionic acid? Like, if I thaw and freeze the DMSO stock every time I make 50ml (and aliquot and freeze as you suggested), is that bad? should I aliquot also the DMSO stock to small amounts? Thanks for the help.