A high-quality sample of DNA is required for a variety of downstream applications like PCR and sequence. DNA purification is the process of removing contaminants such as proteins and other components of the cell, from a sample to make an uncontaminated nucleic acid solution ready for use. There are a myriad of DNA purification techniques, each with their particular advantages and disadvantages based on the base material or application.
The first step of DNA purification is to eliminate protein from the sample with a protease (proteinase enzyme) or mechanical disintegration. After eliminating the cellular debris, the DNA is precipitated in the presence of ethanol, which results in a stringy white precipitate. The DNA precipitated by ethanol can be resuspended, either in water or in a pure solution. The concentration of DNA can be determined by spectrophotometry, based on the nucleic acid absorbance peak at 260nm.
Another popular method for DNA purification is salting out, where a cellulose column is used to capture and bind DNA. The cellulose matrix has to be pretreated with detergents in order to remove any contaminants. A wash buffer is then applied to eliminate the salts. DNA binds to the matrix in low salt conditions and contaminating proteins as well as RNA can be cleaned by using higher salt solutions. The eluted DNA and RNA are then recovered by http://www.mpsciences.com/2021/04/23/dna-purification-processes-for-different-applications/ ethanol precipitation.
Anion exchange is also a well-known method for purifying DNA. This method utilizes a cation-exchange resin to attract positively-charged DNA molecules, while neutralizing resins allow negatively charged DNA to be flushed out of the column. After the DNA has been eluted it can be concentrated using centrifugation. Then, the DNA can be separated by washing it off with 70% ethanol at ice-cold temperatures.