Ethanol Precipitation of Nucleic Acids
Materials
- Cold 100% ethanol
- Cold 70% ethanol
- 1 M sodium acetate
- Centrifuge cooled to 4°C
- Heat block warmed to 37°C
Protocol
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Transfer nucleic acid to a container where it occupies less than one quarter of the total volume (e.g., a 1.5 mL tube should have no more than 375 μL of nucleic acid solution).
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Add one tenth of the nucleic acid volume of sodium acetate buffer to equalize the ion concentrations.
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Add 2-3 volumes of cold 100% ethanol and place the sample in a -20°C freezer for at least one hour.
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Centrifuge sample for 15 minutes at 12000 x g at 4°C.
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Remove as much of the supernatant as possible. Be careful not to disturb the pellet. If you get all the liquid out then skip step 6.
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If not then re-centrifuge briefly, then remove the rest with a 200μL pipette.
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Add 250 μL of cold 70% ethanol.
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Centrifuge for 5 minutes in a 4°C centrifuge at maximum speed.
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Remove supernatant with a 200 μL pipette; evaporate remaining ethanol in a 37°C heat block. Do not do this for too long because overdrying the pellet can make it difficult to resuspend.
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Resuspend pellet in desired volume of water or TE buffer.