Ethanol in my RNA/TE buffer

Dr. Hiranya S. Roychowdhury hroychow at
Thu Jun 24 16:15:55 EST 2004

Residual ethanol really doesn't stick around long.  But, if you want to run a 
sample of your nucleic acid on a gel, make sure the etoh is gone; for it makes 
the sample float up due to "violent" mixing between the etoh and the aqueous 
buffer.  Additionally, some downstream reactions are sensitive to etoh.  

However, it is a good idea not to let the RNA pellet dry up too much before the 
addition of TE or water.  Very dry RNA is very , very hard to resuspend in 
aqueous solvents (don't ask me why, I don't know the answer to that).  Same is 
true for very large DNA, eg. genomic DNA preparations.  So, the best way to 
deal with the balance between etoh and drying is to add the aqueous buffer 
immediately after the etoh is aspirated out and then to subject the resuspended 
NA to a quick (1min) speedvac.  In the absence of speedvac, leaving the tube in 
a 37 C incubator for about 5min also does the trick.

Quoting Mark Ledesma <mledesma at>:

> I know it is customary when washing an RNA pellet with 75% ethanol to
> dry the ethanol off the pellet before suspending it in TE buffer.
> Could someone kindly explain why?
> Someone I know who looks kind of like me (it isn't me, really) just
> forgot to dry his pellet and surely has some ethanol in with his RNA
> and TE. How bad is this?
> Thanks for any help,
> Mark Ledesma

Hiranya S. Roychowdhury, Ph.D.
Coll. Asst. Professor,
Molecular Biology,
Dept. of Chemistry & Biochemistry
Rm# 336, Chemistry Bldg.; MSC 3MLS
New Mexico State University
Las Cruces, NM 88003

More information about the Methods mailing list