title: Writhe formulas and antipodal points in plectonemic DNA configurations.
abstract: The linking and writhing numbers are key quantities when characterizing the structure of a piece of supercoiled DNA. Defined as double integrals over the shape of the double helix, these numbers are not always straightforward to compute, though a simplified formula was established in a theorem by Fuller [Proc. Natl. Acad. Sci. U.S.A. 75, 3557 (1978)]. We examine the range of applicability of this widely used simplified formula, and show that it cannot be employed for plectonemic DNA. We show that inapplicability is due to a hypothesis of Fuller theorem that is not met. The hypothesis seems to have been overlooked in many works.
authors.affiliation: Institut Jean le Rond d'Alembert, CNRS and UPMC Univ. Paris 6, 4 Place Jussieu (case 162), 75005 Paris, France.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Neukirch
authors.forename: Eugene L
authors.initials: EL
authors.lastname: Starostin
mesh_terms: D004278:DNA, Superhelical / Q000737:chemistry*; D008958:Models, Molecular; D009690:Nucleic Acid Conformation
chemical_list: D004278:DNA, Superhelical