DNA purification is among the most common and important procedures in molecular biology. The aim of DNA purification is to isolate the desired genetic material, chromosomal material from the contaminant (proteins, cell membranes, and RNA). This is a crucial step in virtually all molecular processes and must be performed correctly to obtain high-quality, usable DNA.
There are many different approaches for DNA purification. The selection is based on a variety of factors like the source materials, downstream applications, cost, and time constraints. The standard genomic and plasmid purification protocols involve chemical treatment, enzymatic digesting or mechanical disruption of cells or tissues and then salting out proteins and then precipitating the DNA with alcohol.
Ethanol precipitation is an easy, inexpensive 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 out of solution using the highest concentrations of alcohol. This method is used to remove organic compounds, and other impurities. It is usually employed in conjunction with other purification methods.
Another method used for DNA purification is anion exchange chromatography. The interaction between negatively charged DNA phosphate backbones and positively-charged surface molecules of resins binds DNA in a solvent to positively-charged resins. During the binding process removal of contaminants is accomplished making use of a strict washing process. The purified DNA then is eluted in low-salt conditions.