THE USE OF AN ETHIDIUM ANALOGUE IN THE DYE-BUOYANT DENSITY PROCEDURE FOR THE ISOLATION OF CLOSED CIRCULAR DNA: THE VARIATION OF THE SUPERHELIX DENSITY OF MITOCHONDRIAL DNA

Abstract
The separation between open and closed circular DNA in buoyant CsCl gradients containing intercalating dyes depends on the superhelix density of the closed form. These separations are about 1.8 times larger with propidium iodide than with ethidium bromide. The superhelix densities of mitochondrial DNA from HeLa cells and Lytechinus pictus eggs appear to be about two thirds that of mitochondrial DNA from rat and rabbit liver.