Methods for Isolating DNA:Plasmid DNA: Methods for purifying plasmid DNA all basically depend on the concept that plasmids are small and that they are closed supercoiled circles. Lysing the cells: The first step in all cases is to lyse the cells. There are various ways of doing this. The most gentle (and therefore the least likely to result in mechanical disruption of larger plasmids) is to incubate the cells with an enzyme called lysozyme. This breaks down the peptidoglycan cell wall of the bacterium, exposing the cell membrane. In the most gentle procedures, this is done isoosmotically in a
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