Flash freezing ChIP samples without liquid nitrogen? - (Apr/30/2015 )

I guess this would be more of peoples opinion rather than a definitive yes/no answer, but....

I'm doing ChiP with tissue that I have to dissect in very small batches once a day, then flash freeze until I have enough to do a ChIP. Problem is the liquid nitrogen I need to use to freeze them is often in short supply, and a pain in the ass to get, and it seems very wasteful to use an aliquot just to freeze one eppendorf every day. Same problem with the alternative of dry ice/EtOH.

However, I do have access to a -150'C freezer, my question is: do you think freezing my samples in the -150'C freezer would be ok for my ChIP samples? The samples are maximum <20ul in volume (I'm doing Drosophila larval wing discs), and when I tested it the sample froze in under a minute. But I don't want to waste a lot of time gathering tissue and freezing it this way if it's going to affect my abillity to ChIP.

Any ChIP experts care to give their opinion? Thanks!

You can flash freeze in a dry ice/ethanol bath, and then put it at -150, if dry ice is more easily available.

Thank you for your suggestion, and yes I will be trying dry ice when I can get my hands on it, but the fact that we have a freezer that is so available would save so much time and effort, so I'm wondering what the opinion on freezing using that method is.

Cheers