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.
- If the volume of the DNA is less than 200 µl,
bring the volume up to 200 µl with sterile dH2O.
- Add 1/10 th volume of 3M sodium acetate to the DNA
solution and mix. (i.e. add 20 µL to the 200µL solution)
- 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.
- 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!!
- 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!
- You can speedvac the DNA to dryness if any liquid remains.
- Resuspend DNA in appropriate volume of TE or water. (20 µL is typical)
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