Storage of RNA

[Rosamund Eira Powles]

I have been storing RNA samples from both E.coli and Thiobacillus 
ferrooxidans in DEPC water or RNA storage buffer, 20mM sodium phosphate pH   
6.5  1mM EDTA.  The T.ferrooxidans appears to be ok on a agarose gel, but no 
longer gives good results on a Northern Blot, and I presume this is due to 
degradation of the RNA.  I store the RNA at -70 C and thaw and refreeze it 
every time I use it, so this could also be causing problems.  I see some 
people store their RNA in formamide at -20 C, how do they then get rid of 
the formamide, when they want to do primer extension for example?  If anyone 
has any helpful suggestions please could you let me know, I will store my 
RNA in aliquots to prevent too much thawing and freezing, in case that is 
the problem.
Ros Powles
UCT Micriobiology