Isopropanol, Water, and RNA Stability - (Nov/28/2011 )

I was recently having a discussion with someone who remarked in passing that RNA stability is higher in isopropanol than in H2O. (I am preparing to perform a phenol:chloroform extraction of RNA, and they recommended - for added stability - that I keep the RNA in isopropanol instead of H2O until I'm ready to use it).

What is the chemical/biological basis for the increased stability of RNA in isopropanol? I assume it has to do with the higher polarity of isopropanol relative to water?

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Obviously I need to go back and review OChem - isopropanol is LESS polar than water and has a slightly higher pka than water (16 vs 15.7).

RNAses are not active in alcohol, so keeping RNA precipitated as a pellet after ethanol or isopropanol precipitation can help preserve it. You have to get rid of the RNAses anyway, since they will still be around if you redissolve the pellet, so this is not a substitute for careful RNAse free work.

Thanks! I'm learning all sorts of new things today. ...As a side question, because I am curious, why does alcohol inhibit RNase activity? (Assuming it's known...)

I would say the same way it inhibits any other protein, it denatures them.