DNA purification is a standard and important procedure in molecular biology. Purification of DNA is targeted at getting rid of the desired genetic material (chromosomal material) from contaminants such as proteins, RNA, and the cell membrane. This is an essential process in nearly every molecular procedure and must be executed correctly in order to obtain the highest quality, usable DNA.
There are a number of different methods that can be used for DNA purification, the selection of which is dependent on a number of factors, including the starting materials and downstream applications, as well as cost and time limitations. The standard genomic and plasmid purification methods involve chemical treatment, enzymatic digesting or mechanical disruption of tissue/cells followed by salting of the proteins and removing the DNA using alcohol.
Ethanol precipitation can be described as a simple, cost-effective and fast method for desalting and concentration of DNA. DNA molecules form aggregates in the presence of monovalent cations like sodium, and then are filtered out of solution by the highest concentrations of ethanol. This method is employed to remove salts, organic compounds and other impurities. It is often utilized in conjunction with other purification methods.
Anion exchange chromatography is yet another well-known method for DNA purification. DNA in a solution is bonded to positively charged resins via the interaction between the negatively charged DNA phosphate backbone and the positively charged surface molecules of the resin. During the binding and washing processes removal of contaminating molecules from the DNA using strict washing steps, and the DNA that has been purified is eluted in low salt conditions.