Ammonium acetate DNA precipitation method

If you want to obtain pure DNA, you often rely on the method of ammonium acetate DNA precipitation. This method is also very delicate, allowing DNA to precipitate from complex mixed systems and obtain high-purity quality.

Prepare ammonium acetate solution first, the amount and concentration are determined according to the characteristics of the sample and the experimental requirements. Place the sample containing DNA carefully in a container, and slowly add the ammonium acetate solution, stirring it gently to ensure that the two are uniform. For ammonium acetate, ammonium ions and acetate ions are dissociated in the solution. The ammonium ions can attract the negative charge on the DNA phosphate skeleton, causing the charge state of the DNA molecule to change and the solubility to change accordingly.

Then, add an appropriate amount of absolute ethanol or isopropanol. The addition of alcohols can reduce the solubility of DNA in solution. Because DNA is hydrophilic, alcohols and water are mutually soluble, but DNA is sparse. This hydrophobic effect causes DNA molecules to aggregate with each other. After this step, DNA gradually precipitates out of the solution in a flocculent or precipitated state, visible to the naked eye.

To be precipitated, turn it at the speed of the centrifuge. The speed of the centrifuge depends on the sample size and the specifications of the centrifuge tube. Usually at a suitable speed, the DNA precipitate is tightly gathered at the bottom of the tube. Pour the supernatant, which contains unprecipitated impurities, and discard it. Retain the precipitate, which is the crude DNA product to be obtained.

However, the precipitation may still contain some impurities, so it needs to be lightly washed with 70% ethanol. After washing with ethanol, the residual ammonium acetate and other soluble impurities can be removed without damaging the DNA. After washing, centrifuge, discard the supernatant, and when the ethanol evaporates naturally, the DNA precipitation can be dried immediately.

The method of DNA precipitation with ammonium acetate can effectively enrich and purify DNA, providing a high-quality template for subsequent molecular biology experiments, such as PCR, sequencing, cloning, etc. It is an essential method for molecular experiments.