How to "Clean" DNA
(ethanol precipitation protocol)

Anytime DNA has to be "cleaned", this means that all of the proteins, small nucleic acids and salts need to be removed from a solution that contains sizeable dsDNA. To do this, we have to precipitate the DNA.

  1. If the volume of the DNA is less than 200 µl, bring the volume up to 200 µl with sterile dH2O.
  2. Add 1/10 th volume of 3M sodium acetate to the DNA solution and mix. (i.e. add 20 µL to the 200µL solution)
  3. Add 2 volumes (i.e. 400 µL) of -20° C 100% ethanol (EtOH) and vortex for 10 seconds. Put the tube in a -20° C freezer overnight or a -70° C freezer for 20 minutes.
  4. Spin in a microfuge for 5 minutes. Invert the tube with the lid closed and look for the pellet. While upside down, pour out the EtOH but save the pellet!!
  5. Wash the pellet with 500 µl of 4° C 70% EtOH, gently roll the tube, then dump the EtOH, and speedvac the pellet. SAVE THE PELLET!
  6. You can speedvac the DNA to dryness if any liquid remains.
  7. Resuspend DNA in appropriate volume of TE or water. (20 µL is typical)

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