Department of Biological Sciences,

1000 Hilltop Circle

Baltimore, MD 21250

Ethanol Precipitation of DNA

Materials: see Solutions for Recipes

	3 M sodium acetate pH 5.2 or 5 M ammonium acetate
	DNA
	100% ethanol

1.  Measure the volume of the DNA sample. Adjust the salt concentration by adding 1/10 volume of sodium acetate, pH 5.2, (final concentration of 0.3 M) or an equal volume of 5 M ammonium acetate (final concentration of 2.0-2.5 M). These amounts assume that the DNA is in TE only; if DNA is in a solution containing salt, adjust salt accordingly to achieve the correct final concentration. Mix well. Add 2 to 2.5 volumes of cold 100% ethanol (calculated after salt addition). Mix well.
2. Place on ice or at -20 degrees C for >20 minutes.
3. Spin a maximum speed in a microfuge 10-15 min.Carefully decant supernatant. Add 1 ml 70% ethanol. Mix. Spin briefly. Carefully decant supernatant. Air dry or briefly vacuum dry pellet.
4. Resuspend pellet in the appropriate volume of TE or water.

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Last updated on 3/2/2010