1. Field of the Invention
The present invention relates to a method for isolating a plasmid deoxyribonucleic acid (DNA) from nucleic acids which is one of the most basic operations in the field of genetic engineering.
2. Description of the Related Art
Hitherto, mass production of a target DNA by integrating and culturing the target DNA into a plasmid vector of coli bacteria (Escherichia coli) has been widely carried out in the field of genetic engineering.
At present, in the mass production of a target DNA the plasmid vector has been recovered from the coli bacteria by conducting bacteriolysis, followed by the removal of the genomic DNA, proteins, etc., to obtain a mixture of ribonucleic acid (RNA) and plasmid DNA. Some well-known methods for the recovery of the plasmid vector include an alkali-SDS (sodium dodecyl sulfate) method, etc. Furthermore, in order to obtain a purified plasmid DNA from the mixture of RNA and plasmid DNA, a column separation method using an ion-exchange resin, a density-gradient centrifugation method using cesium chloride and the like, have generally been used as the separation method.
However, the above-mentioned separation methods have several drawbacks. For example, since the target plasmid DNA is obtained after having been diluted with a voluminous amount of an eluting solution, the column separation method using an ion-exchange resin requires a troublesome concentration of the eluted plasmid DNA. Furthermore, since centrifugation must be carried out in a large scale centrifugal apparatus at a high revolution for a long period of time, the density-gradient centrifugation method requires the greatest of care which makes centrifugation troublesome and uneconomical.