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  • Title: The unwinding of circular DNA by intercalating agents as determined by gel electrophoresis.
    Author: Dougherty G.
    Journal: Biosci Rep; 1983 May; 3(5):453-60. PubMed ID: 6688368.
    Abstract:
    The conventional counting of electrophoretically resolvable topoisomers is an attractive technique for determining the number of superhelical turns in a closed circular DNA molecule. The method can be extended in order to determine the unwinding produced by a drug, if its binding constants are known under similar environmental conditions. Ethidium bromide was found to unwind a DNA molecule derived from the plasmid pBR322 by 26.0 degrees in a magnesium-containing buffer. The method is convenient for investigating the possible effects of different environmental changes (such as ionic strength, ionic species, or temperature) on the unwinding angle produced by a particular drug. It can also give an early indication of multiple modes of binding.
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