Highly purified plasmid DNA from Escherichia coli are required to obtain reliable sequencing results. This purification is based on the differential denaturation of chromosomal and plasmid DNA.
Lysis solution containing sodium dodecyl sulfate (SDS) and sodium hydroxide denatures both chromosomal and plasmid DNA in bacterial culture. Neutralization with potassium acetate allows only plasmid DNA to reanneal and stay solubilized. Most of the chromosomal DNA and proteins precipitate in a complex formed with potassium and SDS.