Molecular Cloning Fourth Edition, A Laboratory Manual, by Michael R. Green and Joseph Sambrook

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Precipitation of DNA with Isopropanol

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DNA is less soluble in solutions containing isopropanol than in solutions containing ethanol. In contrast to precipitation with ethanol, which requires 23 volumes of alcohol, precipitation with isopropanol is performed with 0.60.7 volume of alcohol. Isopropanol is often the better choice when precipitating DNA from large volumes of solution. Precipitation with isopropanol is performed at room temperature to lessen the risk that solutes like sucrose or sodium chloride will be coprecipitated with the DNA. However, isopropanol also has some disadvantages.

  • Salts are less soluble in solutions consisting of 35 isopropanol than in solutions containing 65 ethanol.
  • The pellets of DNA are translucent and are difficult to see. Isopropanol is less volatile than ethanol and is therefore more difficult to remove.
  • Finally, DNA precipitated by isopropanol does not stick tightly to the wall of the microcentrifuge tube and is easily lost when the isopropanol solution is removed or when the pellet is washed with ethanol (Step 5, below).


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(Limited time special offer.) Molecular Cloning Fourth Edition, A Laboratory Manual, by Michael R. Green and Joseph Sambrook
Molecular Cloning Fourth Edition, A Laboratory Manual, by Michael R. Green and Joseph Sambrook

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