pH of water; dissolving RNA

Chi-kuang Wen ckwen at
Fri Feb 21 16:46:40 EST 1997

Achim Recktenwald, PhD (achim at wrote:
: Hildur V. Colot wrote:
: > 
: > Can someone enlighten me on the pH to be expected of, say. Milli-Q
: > water?  I'm in a new lab and I swear that RNA pellets are not dissolving
: > as well as they used to.  The pH of the water (after autoclaving) is 6.3
: > on a meter and from 5 to 6 on different pH strips.  Is it a really bad
: > idea to dissolve the RNA in TE at pH 7.5 before running it on a
: > formaldehyde gel?  I will also refrain from drying it in a Speedvac,
: > something I used to do without any problem.

 CO2 in the air makes pure water slightly acidic.
I used to dissolve my RNA in water, store at -70C for 3-4 years. Recently
I got a chance to do Northerns with those RNAs.  It turns great, no degradation, and signals are as clear as they were.
If you just want to run your RNA on gel, an alternative is to dissolve
your RNA in deionized formamide, and run directly on a formamide/formaldehyde


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