Biology Protocols

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Ethanol Precipitation of Nucleic Acids

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  • 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) and mix well. Note: These amounts assume that the DNA is in TE or water only; if DNA is in a solution containing salt, salt should be adjusted accordingly to achieve the correct final concentration.
  • Add 2 to 2.5 volumes (calculated after salt addition) of ice-cold 100% ethanol and mix well (For RNA precipitation use 2.5 to 3 volumes).
  • Place on ice or at -20 degrees C for >20 minutes (the longer you leave it the better the yield).
  • Spin at maximum speed in a microfuge 10-15mins.
  • Carefully decant supernatant.
  • Add 1 ml 70% ethanol and mix.
  • Spin at maximum speed in a microfuge for 5mins.
  • Carefully decant supernatant and air dry or briefly vacuum dry pellet.
  • Resuspend pellet in the appropriate volume of TE or water.


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