NH4Ac and EtOH precipitation of DNA

Add NH₄Ac (10 M stock or solid) to the sample for a final concentration of 2.5 M, mix (spin at 4℃, transfer the supernatant to a new tube; optional spin for extra purification of the DNA), add 2.5 volumes of EtOH, mix, and spin this time keeping the pellet (watch the liquid as pouring it down the drain to make sure that pellet does not come loose). Turn the tube upside down on a paper towel to allow the EtOH to drain well. Give the pellet a 70 % EtOH rinse (carefully and a little slowly add the EtOH by a DPTP: if the pellet comes loose, spin it again), drain the tube again, and dry the pellet briefly (under the vacuum for 5 to 10 min) before resuspending the DNA in 10:2 TE (almost always TE except doing a digest or ligation in which case the DNA is resuspended in H₂O:low salt in the resuspension buffer is important). Often multiple NH4Ac/EtOH precipitation are desired. If the DNA is particularly important or if it is at a very low concentration i.e. <0.5 µg/ml, it is best to include a waiting period before each spin: at least one hour (overnight is better) and at either room temperature or 4 ℃. EtOH and salt reduce the solubility of DNA, consequently, it is best to drain the EtOH well, wiping the inside of the tube with a Chimwipe (but, do not touch the pellet)

Sample Volume of Table

 　   　MFT(0.5 ml) 　　　     MFT(1.5 ml) 　　　  Corex  　　　　　　　ORT 250ml
DNA 　　105 μl 　210 μl  　　315 μl  　　　　　 2.1 ml  　9 ml 　　　 60.0 ml
NH4Ac  　35 μl  　70 μl  　　105 μl  　0.7 ml   　　3 ml 　 12.6 g
EtOH 　　350 μl 　700 μl 　　1050 μl 　　　　 　7.0 ml  　30 ml 　　　165.0 ml

Optional spin check:

Min/rpm 　　15/14K  　　　　　　20/14K  　　10/14K      　　　　　　25/9K
Min/rpm 　　20/14K 　20/14K 　　20/14K  　　20/14K 　　20/14K 　　25/9K