size Plasmid preparation can be divided into five main categories based on the scale of the preparation: minipreparation, midipreparation, maxipreparation, megapreparation, and gigapreparation. The choice of which method to use will depend on the amount of plasmid DNA required, as well as the specific application for which it will be used. Kits are available from varying manufacturers to purify plasmid DNA, which are named by size of bacterial culture and corresponding plasmid yield. In increasing order they are: miniprep, midiprep, maxiprep, megaprep, and gigaprep. The plasmid DNA yield will vary depending on the plasmid copy number, type and size, the bacterial strain, the growth conditions, and the kit. Minipreparation Minipreparation of plasmid DNA is a rapid, small-scale isolation of plasmid DNA from bacteria. Commonly used miniprep methods include alkaline lysis and spin-column based kits. It is based on the alkaline lysis method. The extracted plasmid DNA resulting from performing a miniprep is itself often called a "miniprep". Minipreps are used in the process of molecular cloning to analyze bacterial clones. A typical plasmid DNA yield of a miniprep is 5 to 50 µg depending on the cell strain. Miniprep of a large number of plasmids can also be done conveniently on filter paper by lysing the cell and eluting the plasmid on to filter paper. Midipreparation The starting E. coli culture volume is 15-25 mL of Lysogeny broth (LB) and the expected DNA yield is 100-350 µg. Maxipreparation The starting E. coli culture volume is 100-200 mL of LB and the expected DNA yield is 500-850 µg. Megapreparation The starting E. coli culture volume is 500 mL – 2.5 L of LB and the expected DNA yield is 1.5-2.5 mg. Gigapreparation The starting E. coli culture volume is 2.5-5 L of LB and the expected DNA yield is 7.5–10 mg. Purification of plasmid DNA It is important to consider the downstream applications of the plasmid DNA when choosing a purification method. For example, if the plasmid is to be used for transfection or electroporation, a purification method that results in high purity and low endotoxin levels is desirable. Similarly, if the plasmid is to be used for sequencing or PCR, a purification method that results in high yield and minimal contaminants is desirable. However, multiple methods of nucleic acid purification exist. All work on the principle of generating conditions where either only the nucleic acid precipitates, or only other biomolecules