DNA purification is a common and important procedure in molecular biology. Purification of DNA is targeted at separation of the desired genetic material (chromosomal material) from contaminants such as proteins or RNA as well as the cell membrane. This is a vital step in almost every molecular application and must be done correctly in order to obtain high-quality and usable DNA.
There are several different methods for DNA purification. The selection is based on a range of factors like the source materials and downstream applications, cost and time limitations. The most common genomic and plasmid DNA purification procedures include chemical treatment, enzymatic digestion, or mechanical disruption of tissue/cell samples followed by salting-out of the proteins and precipitation of the DNA using ethanol.
Ethanol precipitation can be a low-cost simple and quick method of desalting and concentrating DNA. DNA molecules form aggregates in the presence of monovalent cations such as sodium and are then precipitated from the solution by using high levels of alcohol. This technique is used to remove organic compounds and other impurities. It is usually utilized in conjunction with other purification methods.
Anion exchange is another popular method for DNA purification. The interaction between the negatively-charged DNA phosphate backbones as well as the positively charged surface molecules of resins bind DNA in a solvent to positively charged resins. During the binding and washing processes removal of contaminating molecules from the DNA via rigorous wash steps. The purified DNA is eluted in low salt conditions.