A high-quality DNA sample is required for a range of downstream applications, such as PCR and sequencing. DNA purification is the process of eliminating contaminants such as proteins and other cellular components, from a sample to make an uncontaminated nucleic acid solution ready for use. There are a wide variety of DNA purification methods available each with distinct advantages and disadvantages dependent on the source material and the intended application.
The first step in DNA purification is removing proteins from the sample using the proteinase (protein enzyme) or mechanical disruption. After getting rid of the cellular debris the DNA is precipitated in ethanol, resulting in the formation of a white and stringy precipitate. The precipitated DNA is then resuspended in water or a sterile buffer. The DNA concentration can be determined using spectrophotometry using the nucleic acid absorbance peak at 260nm.
Salting out is yet another popular method used to purify DNA. A column of cellulose is utilized in this process to capture and bind DNA. The cellulose matrix is pretreated using detergents to get rid of contaminants, and a wash buffer is utilized to wash away the salts. DNA binds to matrix under low salt conditions, and contaminating proteins and DNA can be eliminated by using higher salt solutions. The eluted DNA and RNA are then recovered by precipitation with ethanol.
Anion exchange chromatography can also be a well-known method for DNA purification. This method employs a resin that draws positively charged DNA purchase science supplies molecules, and a resin that neutralizes negatively-charged molecules of RNA is used to clean the column. Once the DNA is removed from the anion exchange column, it can be concentrated by centrifugation and washed with ice-cold 70% ethanol to precipitate the DNA.