Automated Purification of Plasmid DNA Using Paramagnetic Particles

We describe a reagent system and robotic method for purifying plasmid DNA for restriction digestion, PCR, and fluorescent sequencing applications. The method uses two types of Wizard® MagneSilTM paramagnetic particles. Following lysis and neutralization procedures, the first particle type binds and removes cell debris; the second type is then used to bind plasmid DNA from the cleared lysate. The particles are then washed to eliminate unwanted contaminants. Purified plasmid DNA is then eluted from the particles with nuclease free water. When using a cell mass of approximately 4 O.D.₆₀₀, the yield is 10–12μg of DNA when using high copy number plasmid. When used in BigDye® terminator sequencing, these DNA templates typically yield read lengths greater than 700 bases and Phred 20 scores of 600 to 750 bases. This purification method has been adapted for use on several robotic platforms in a 96-well format.