Plasmid purification is a rather classical experiment, but the technique is still developing for time- and cost- saving. The critical principle is based on the alkaline lysis method, although the following steps have several variations. The needed purities and/or quantities of DNA depend on researches using isolated plasmids, meaning that more reasonable method can be selected in each experiment. For example, a non-alkaline-lysis method such as boiling method is still available. One of the important steps for purifying plasmid is a removal of RNA. Ribonuclease is usually used for removing RNA from plasmid sample. On the other hand, a kind of salts such as lithium and calcium functions to make RNA as a selective precipitate from DNA-RNA mixture. Based on these backgrounds, the technique to purify plasmid DNA has been discussed.
Part of the book: Plasmid