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What is DNA purification?  

First performed by Friedrich Miescher in 1869, DNA isolation uses a mixture of physical and chemical methods to purify samples of DNA.

In the past, DNA isolation involved organic extraction combined with ethanol precipitation. The multiple-day plasmid purification protocol included banding with caesium chloride banding before the plasmid DNA was subjected to dialysis. However, many of the reagents used in these methods were hazardous, and the process overall time consuming.

Nowadays, most molecular biology assays include DNA purification as a standard procedure. There are a range of different kits available for DNA extraction and purification. These can save scientists time and help them optimise their DNA isolation procedures.

DNA purification kits currently on the market use much safer methods and can perform DNA isolation over a shorter time period – an hour or less. Cells are disrupted using detergents, chaotropic salts or alkaline denaturation. The lysate which is created as a result is cleaned via filtration, centrifugation or magnetic clearing. The soluble portion of the lysate is then treated to obtain purified DNA.

The resulting high-quality DNA can be used for a range of downstream applications, including sequencing reactions and multiplex PCR.

How does DNA purification work?

Depending on your tissue or cell samples, you can use chemical treatment, enzymatic digestion or mechanical disruption to lysate the DNA. Removing contaminants from the nucleic acids and using a suitable buffer solution to precipitate the samples will aid the purification of the DNA.

To determine which purification method is best for your DNA sample, you should consider different criteria, from the source organism and starting material to the target nucleic acid, downstream application and, of course, the desired results.

There are a number of genomic and plasmid DNA purification products designed to make the isolation process less time-consuming. These are suitable for wide array of routine molecular biology applications, including high throughput screening.

What does DNA extraction involve?

As we discussed above, DNA extraction kits are designed to help scientists isolate DNA from various types of samples and cells. While methods can somewhat vary between particular labs, extracting DNA from the cell nucleus commonly involves three key steps:

Cell breakdown

The first step to isolating the DNA of interest is breaking the cell open by lysis and extracting its intracellular contents. Once individual cells from the sample are separated out and immersed into a salty solution, a detergent is added to break down the cell lipids.  With these membranes are pried open, DNA material is released. 

Clearing out proteins

There are a few different methods commonly used to clear the DNA sample from debris. DNA-associated and cell proteins are usually degraded using a protein enzyme or filtered out from the sample.

DNA precipitation & purification

Whereas DNA is soluble in water, it cannot be dissolved in an environment where salt and alcohol are present. That’s why alcohols such as isopropanol or ethanol are stirred into the DNA sample with a sterile pipette to help separate out a precipitate, which can then be spooled out. Once precipitated, the DNA is purified further still and immersed in a slightly alkaline buffer, ready to be used.

DNA quality check

Before carrying on with the rest of the assay, scientists take optical density readings or use gel electrophoresis to determine the quality and concentration of DNA material in the sample. If the DNA is both present and pure, downstream applications can go ahead.

What can this DNA be used for?

The purified DNA extracted during this procedure can be used for various types of molecular analysis such as sequencing, electrophoresis, PCR and molecular cloning.

Why DNA purification is important

The fields of molecular biology, clinical research, genomics and biotechnology consider DNA purification an essential part of their scientific methods which helps them determine whether immediate and downstream applications have been successful.  

DNA purification helps extract genomic and/or plasmid DNA in the sample quantities that your research requires. Purifying your DNA samples from contaminants also extends their shelf-life and reduces the probability of error when it comes to research results.