Writhe formulas and antipodal points in plectonemic DNA configurations.
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.
Neukirch
Sébastien
S
Institut Jean le Rond d'Alembert, CNRS and UPMC Univ. Paris 6, 4 Place Jussieu (case 162), 75005 Paris, France.
Starostin
Eugene L
EL
D004278:DNA, Superhelical / Q000737:chemistry*; D008958:Models, Molecular; D009690:Nucleic Acid Conformation
D004278:DNA, Superhelical