Can DMSO expire? - (May/06/2009 )

Hi

(sorry if i post in the wrong forum but im new here)

Im confronted with a confusing problem right now.
I have severel apoptosis-inducing agents (namely actinomycinD, staurosporin, camptothecin and etoposide), all of which i dilluted in DMSO and stored in aliquots according to the manual ( --> -20°C).

lately, all of those agents stopped working. apoptosis is not induced anymore. I made sure that my detection assay is working correctly (i assay caspase 3 activity), meaning that i have positive controls (TNFalpha induced apoptosis) that work.
Also, these chemicals used to work some time ago.....

my only idea right now is that ,since they are all stored in DMSO, this DMSO is somehow expired. the bottle is rather old ,but somehow i doubt that DMSO can expire or get unstable under these conditions. the dmso itself is keept at RT.

Doese anyone has an idea or experienced similar problems?

I suspect that it is the drugs that have gone off. I know that both camptothecin and actinomycin D are unstable in solution, and I am guessing the other two are as well.

Unfortunately Occam's razor doesn't work in all situations.

bob1 on May 7 2009, 02:14 AM said:

Thanks for your suggestion.

i also thought that this might be the case.if so, is here any method to prove it? like IR spectroscopy or something? But anyway it would be rather odd, since the etoposide for instance never worked.
Lucky for me that these compounds are rather cheep