The need for high quality, highly pure DNA and RNA is important for a wide variety of research and clinical applications. These nucleic acids are being isolated from a variety of sources such as cells (including bacterial cells), PCR reactions, restriction enzyme digestions and agarose gel matrices, to name a few. Purification methods optimized for various sample types have emerged over time. Modifications are made periodically to improve sample quality and yield, reduce processing time, and to ensure compatibility with existing workflows and equipment.
When isolating nucleic acids from cells, the first step is to disrupt the cell membrane to release the DNA. This is often done using chaotropic salts, alkaline denaturation, or detergents. Next, the soluble components of the cell lysate must be separated from the cellular debris and other insoluble materials. Centrifugation and vacuum filtration are frequently used to accomplish this separation, but magnetic clearing has gained wide acceptance more recently. Lastly, the nucleic acids must be separated from the other soluble materials in the lysate, including proteins.
Once the DNA is in solution, regardless of whether it originated from cells or from an enzymatic reaction, there are many different methods that can be employed to isolate it from other soluble components.