DNA Purification Methods

Binding to Microporous Matrices

Examples of this method are:

  • The use of high salt concentrations in the suspension buffer to bind DNA to silica matrices followed by elution using low salt concentrations in the elution buffer.   
  • Ion exchange chromatography using anion exchange membranes.

Mustang Anionic and Cationic Membrane AdsorbersPall has developed unique membrane technology in the form of Mustang™ anionic and cationic membrane adsorbers, which allows purification of nucleic acids and proteins using ion exchange chromatography. The Mustang product line is already established as the technology of choice for nucleic acid removal from process streams, as in part of DNA clearance from therapeutic products like vaccines. The utility of Mustang membrane adsorber modules has also been demonstrated for purification of plasmid DNA, for use as a gene therapy product. Another novel product developed by Pall to streamline nucleic acid purification is the plasmid lysate clearance plate which allows purification of plasmid DNA. For example, these plates can be used as a vector for archiving eukaryotic sequences as part of a bacterial or yeast clone library.

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Size Exclusion

Ultrafiltration (UF) is a membrane separation technique used to separate extremely small particles and dissolved molecules in fluids. The primary basis for separation is molecular size, although other factors such as molecule shape and charge can also play a role. Compared to non-membrane processes, ultrafiltration is gentle, fast, and relatively inexpensive. Methods for purifying nucleic acids using the Pall Nanosep® device, which contains a membrane operating by molecular weight size exclusion, are well established and covered in the application guide, “Nanosep Centrifugal Devices Protocols for Use.” The methods described allow rapid, simple recovery of high yields of purified DNA. The same technology is also available in multi-well plate formats for parallel processing of biological samples requiring purification.

Chemical Extraction

These methods use solvents such as chloroform/phenol to solubilize cellular material and partition the DNA for subsequent purification, e.g., using density gradient centrifugation. The limitation of this method is the disposal issue created by the extraction solvents used and the purity and yield of the DNA recovered.