The unwinding of circular DNA by intercalating agents as determined by gel electrophoresis
- 1 May 1983
- journal article
- research article
- Published by Portland Press Ltd. in Bioscience Reports
- Vol. 3 (5) , 453-460
- https://doi.org/10.1007/bf01121956
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° 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.Keywords
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