Separation of Supercoiled DNA Using Capillary Electrophoresis

DNA supercoiling is a general phenomenon of almost all DNA in vivo. Plasmids, bacterial chromosomes, the mitochondrial genome and many viral genomes occur as closed circular DNA. Even some linear DNAs, such as eukaryotic chromosomes and yeast plasmids, behave like circular DNA because part of the DNA is anchored to the nuclear matrix creating closed-circular loops. Many DNA-associated processes are affected by changes in DNA supercoiling. These processes include the genome organization, transcription, gene expression, DNA replication, and recombination events (1 ). Plasmids are double-stranded circular DNAs which are capable of replicating independent of the chromosome. This property allows plasmids to be carriers of desired DNA sequences and to be replicated in large quantity. Plasmids were actually the first successful DNA vectors used for molecular cloning in bacteria. Recently, the potential of plasmids in gene therapy has been explored extensively. The rising interest in gene therapy for treatment of human diseases, such as cancer and genetic disorders, is reflected in the growing number of clinical trials (2 ,3 ).