Ethanol precipitation of nucleic acids.

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Renumbered during migration. The source protocol began at step 4 and ran to step 13, with no steps 1–3 anywhere. Its step 8 also told you to "skip step 6", which pointed backwards at the ethanol addition rather than forwards at the re-centrifuge step — that cross-reference now points to the correct step. Worth confirming nothing was actually lost from the start of the protocol.

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Materials

• Cold 100% ethanol
• Cold 70% ethanol
• 1 M sodium acetate
• Centrifuge cooled to 4°C
• Heat block warmed to 37°C

Protocol

1. Transfer nucleic acid to a container where it occupies less than one quarter of the total volume — for example, a 1.5 mL tube should have no more than 375 μL of nucleic acid solution.
2. Add one tenth of the nucleic acid volume of sodium acetate buffer to equalize the ion concentrations.
3. Add 2–3 volumes of cold 100% ethanol and place the sample in a -20°C freezer for at least one hour.
4. Centrifuge the sample for 15 minutes at 12,000 × g at 4°C.
5. Remove as much of the supernatant as possible, being careful not to disturb the pellet. If you get all the liquid out, skip step 6.
6. Re-centrifuge briefly, then remove the rest with a 200 μL pipette.
7. Add 250 μL of cold 70% ethanol.
8. Centrifuge for 5 minutes in a 4°C centrifuge at maximum speed.
9. Remove supernatant with a 200 μL pipette, then evaporate the remaining ethanol in a 37°C heat block. Do not do this for too long — overdrying the pellet can make it difficult to resuspend.
10. Resuspend the pellet in the desired volume of water or TE buffer.