DNA Precipitation

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Revision as of 12:10, 10 June 2009 by Michael A. Speer (talk | contribs) (Overview)
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This protocol can be used to concentrate DNA, or to change the buffer the DNA is suspended in. This is usually coupled with phenol chloroform extraction and is used as a way of purifying nucleic acids.

This protocol also works for RNA precipitation (take care to use RNAse free materials in this case).


  • 3M NaOAc pH 5.2
  • EtOH 95%
  • Glycogen (optional)


  1. 1/10 volume NaOAc.
  2. 1ul Glycogen.
  3. 2 volumes EtOH.
  4. -20°C overnight or 30min -80°C.
  5. Centrifuge >12k G for at least 15 mins.
  6. Remove supernatant
  7. Resuspend in desired volume of water/buffer


-20°C for an hour is fine for using larger (1mL of bacterial culture, plasmid) amounts of DNA

The DNA pellet will not always be visible depending on how much DNA you are precipitating. So always take care in loading your samples in the centrifuge to remember the direction they are facing. The DNA pellet will be on the part of the tube facing the outside of the centrifuge.

This protocol will precipitate all nucleic acids, not just DNA. If you do not want RNA in your sample, one of the many ways to deal with it is to simply resuspend in TE + RNAse at the last step and leave it at room temperature for 15mins-1hr.




Discuss this protocol.