Ethanol Precipitation of DNA
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This procedure allows the concentration of DNA samples from dilute solution and the removal of unwanted salts from DNA samples.
Materials
3M Sodium Acetate buffer, pH 5.2 (store at 4 ℃).
Cold 100% Ethanol (-20℃).
Cold 70% Ethanol in sterile dH2O (-20℃).
DNA sample
4 ℃ Microcentrifuge (normal microcentrifuge in cold room works fine). All centrifugations should be on "soft" (no brake) setting.
Procedure
1.Transfer DNA to a container where it fills one fourth the total volume (a 500 µL tube should have no more than 125 µL of DNA solution, for example) .
2.Add one tenth volum of Sodium Acetate buffer to equalize ion concentrations.
3.Add at least two volumes of cold 100% ethanol; let stand in -20℃ freezer for at least one hour.
4.Centrifuge sample for 15 minutes at highest speed in a 4℃ microcentrifuge.
5.Remove as much supernatant as possible with a 1 mL micropipet; recentrifuge, then remove the rest with a 200 µL pipet.
6.Add 200 µL of cold 70% ethanol; centrifuge for 5 minutes in a 4 ℃ centrifuge.
7.Remove supernatant with a 200 µL pipet; evaporate remaining ethanol in a 37 ℃ water bath.
8.Resuspend pellet in desired volume of water or TE buffer.