A novel intact circular dsDNA supercoil is proposed as an alternative to the conventional DNA supercoil, so that the two complementary strands of ssDNA circles are separable without any covalent bond breakage. This new structure can be visualized by using two tubings: one black and one clear. Twist the black tubing a number of times and connect its two ends. Do the same for the clear tubing. Then wrap the two tubings together. This forms the separable or novel supercoil. On the other hand, the conventional supercoil can be modeled by twisting the black and clear tubings together and then connect their respective ends, so that the two tubings are not separable unless one of them is cut. Experimentally, in the absence of any enzyme, many intact plasmid dsDNA circles give two bands on agarose gel electrophoresis under a certain given condition, while the same plasmid molecules after cutting once by a restriction enzyme give only one band under the same, condition. In the case of intact pUC19 plasmids, these two bands can then be, recovered and sequenced separately, using two primers in opposite directions. Each band gives mostly one sequence which is complementary to that of the other band. The combination of the above theoretical model and experimental results strongly suggests that there is an alternative structure of DNA which does not have the usual difficulty of unwinding, rewinding and requiring numerous covalent bond breakages and ligations during semiconservative replication.
This is a preview of subscription content, log in to check access.
Buy single article
Instant access to the full article PDF.
Tax calculation will be finalised during checkout.
Subscribe to journal
Immediate online access to all issues from 2019. Subscription will auto renew annually.
Tax calculation will be finalised during checkout.
Abramowitz, M. and I. A. Stegun. 1964.Handbook of Mathematical Functions. National Bureau of Standards, Applied Mathematical Series 55. Washington, DC: U.S. Goverment Printing Office.
Brahmachari, S. K., Y. S. Shouche, C. R. Cantor and M. McClelland. 1986. Sequences that adopt non-B-DNA conformation in form V DNA as probed by enzymic methylation.J. Mol. Biol.,193, 201–211.
Casey, J. and N. Davidson. 1977. Rates of formation and thermal stabilities of RNA:DNA and DNA:DNA duplexes at high concentrations of formamide.Nucl. Acids Res. 4, 1539–1552.
DiGabriele, A. D. and T. A. Steitz. 1993. A DNA dodecamer containing tract crystallizes in a unique lattice and exhibits a new bend.J. Mol. Biol. 231, 1024–1039.
Driscoll, R. J., M. G. Youngquist and J. D. Baldeschweieter. 1990. Atomic-scale imaging of DNA using scanning tunnelling microscopy.Nature 346, 294–296.
Edwards, P. A. W.. 1978. A sequence-dependent, four-stranded, double Watson-Crick DNA helix that could solve the unwinding problems of double helices.J. Theor. Biol. 70, 323–334.
Franklin, R. E. and R. G. Gosling. 1953. Molecular configuration in sodium thymonucleate.Nature 171, 740–741.
Gehring, K., J.-L. Leroy and M. Gueron, 1993. A tetrameric DNA structure with protonated cytosine-cytosine base pairs.Nature 363, 561–565.
Langridge, R., H. R. Wilson, C. W. Cooper, M. H. F. Wilkins and L. D. Hamilton. 1960. The molecular configuration of deoxyribonucleic acid I. X-ray diffraction study of crystalline form of lithium salt.J. Mol. Biol. 2, 19–37.
Leroy, J.-L. and M. Gueron. 1995. Solution structures of thei-motif tetramers ofd(TCC),d(5methylCCT) andd(T5methylCC): novel NOE connections between amino protons and sugar protons.Structure 3, 101–120.
McGavin, S., H. R. Wilson and G. C. Barr. 1966. Intercalated nucleic acid double helices: a stereochemical possibility.J Mol. Biol. 22, 187–191.
Meselson, M. and F. W. Stahl. 1958. The replication of DNA inEscherichia coli Proc. Natl. Acad. Sci. USA,44, 671–682.
Rich, A. 1995. The nucleic acids. A backward glance.Ann. NY Acad. Sci. 758, 97–142.
Saenger, W. 1984.Principles of Nucleic Acid Structure New York: Springer-Verlag.
Sambrook, J., E. F. Fritsch and T. Maniatis. 1989.Molecular Cloning, 2nd ed. Cold Spring Harbor, NY: Cold Spring Harbor Laboratory Press.
Stasiak, A. 1996. Getting down to the core of homologous recombination.Science 272, 828–829.
Stettler, U. H., H. Weber, T. Koller and C. Weissmann. 1979. Preparation and characterization of form V DNA, the duplex DNA resulting from association of complementary, circular single-stranded DNA.J. Mol. Biol. 131, 21–40.
Watson, J. D. and F. H. C. Crick. 1953. Molecular structure of nucleic acids.Nature 171, 737–738.
Wilkins, M. H. F., A. R. Stokes and H. R. Wilson. 1953. Molecular structure of deoxypentose nucleic acids.Nature 171, 738–740.
Wu, T. T. 1968a. Strandedness of DNA at 92% relative humidity.Bull. Math. Biophys. 30, 681–686.
Wu, T. T. 1968b. Periodic conformations of deoxyribonucleic acids.Bull. Math. Biophys. 30, 687–700.
Wu, T. T. 1969a. A model for the tertiary structure of transfer ribonucleic acid.Bull. Math. Biophys 31, 395–402.
Wu, T. T. 1969b. Secondary structures of DNA.Proc. Natl. Acad. Sci. USA 63, 400–405.
Wu, T. T. 1992. Intact double-stranded DNA plasmid molecules give two bands on agarose gel electrophoresis.FASEB J. 6, A223.
Wu, T. T. 1993. Strand separation of supercoiled intact circular dsDNA.FASEB J. 7, A1289.
About this article
Cite this article
Wu, R., Te Wu, T. A novel intact circular dsDNA supercoil. Bltn Mathcal Biology 58, 1171–1185 (1996). https://doi.org/10.1007/BF02458388
- Intensity Spot
- Complementary Strand
- Layer Line
- Clear Tubing
- Plasmid Molecule