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. 1975 Nov;72(11):4280–4284. doi: 10.1073/pnas.72.11.4280

Action of nicking-closing enzyme on supercoiled and nonsupercoiled closed circular DNA: formation of a Boltzmann distribution of topological isomers.

D E Pulleyblank, M Shure, D Tang, J Vinograd, H P Vosberg
PMCID: PMC388704  PMID: 1060106

Abstract

Highly purified nicking-closing enzyme from mouse cells in 20-fold enzyme/substrate excess converts closed circular native PM2, ColE1, and Minicol DNA into limit product sets of DNAs. Each set has a mean degree of supercoiling of approximately zero. The individual species in the sets differ by deltatau = +/-1, +/-2, etc., and the relative masses fit a Boltzmann distribution. It was also demonstrated that "nonsupercoiled" closed circular duplex molecules serve as substrates for the nicking-closing enzyme, and that a distribution of topological isomers is generated. Polynucleotide ligase, acting on nicked circular DNA, forms under the same conditions, the same set of closed DNAs. The latter enzyme freezes the population into sets of molecules otherwise in configurational equilibrium in solution.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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