Washing RNA pellet - 85% ethanol? - (Nov/26/2010 )

I'm working in a lab which houses two different groups and they both have slightly different protocols for RNA extraction and purification. For the washing step, our protocol says to use 75% ethanol whilst the other group says to use 85%. I asked the technician and he said that he once read a paper that suggested 85% was better, and I'm just wondering why. Does it help to prevent the RNA from dissolving? Would this be at the expense of salt-removal? Their protocol only says to wash a single time.

The higher alcohol concentration helps retain the short pieces of RNA.

In another RNA extraction thread someone said that higher EtOH solutions may not clean out the salts from the RNA sample as well. So different EtOH solutions may have different effects for washing your sample and thus affect RNA sample purity.

WSN on Fri Dec 17 13:40:26 2010 said: