Desalting with butanol precipitation (w/ a reminder)

Hiranya S. Roychowdhury hroychow at
Sun May 21 11:13:05 EST 2000

The use of n-butanol in "precipitating" oligonucleotides (as you put it) is
diffrent from what is meant when etoh or 2-propanol is used. The deprotected
oligos come in very small volumes and straight butanol used for the clean up
works by absorbing the ammonium hydroxide (aka aqueous ammonia) and other
salts along with the water. What remains back is the nucleic acid that does
not get absobed into the butanol. You then remove the n-butanol and the tube
should have only the nucleic acids and no aqueous stuff. 
If you use buffer- or water-saturated n-butanol, you will not obtain any
"precipitate" or dry oligos. You will then be left with approximately the
original volume of the oligos, minus the ammonia, etc.

At 11:56 PM 5/19/00 GMT, Jouko Kalevi Pettersson wrote:
>In article <200005191948.NAA260066 at nestor.NMSU.Edu>, Hiranya S. Roychowdhury
>>BTW, butanol is immiscible with water (although it absorbs it) and will NOT
>>precipitate DNA or RNA as you originally enquired.
>It absorbs about 10% water. It is used to precipitate oligonucleotides.
>Jouko Pettersson              Internet: Jouko.Pettersson at Helsinki.FI
>Division of Biochemistry      FAX:      +358 9 191 59068
>Department of Biosciences     Phone:    +358 9 191 59012
>University of Helsinki

Dr. Hiranya Sankar Roychowdhury
New Mexico State University
Las Cruces, NM 88003
Ph. (505) 646-5785
hroychow at


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