Stretching DNA: Role of electrostatic interactions
Institute of Physical Science and Technology, University of Maryland, College Park,
Maryland 2074, USA
Revised: 9 June 1999
Published online: 13 August 2012
The effect of electrostatic interactions on the stretching of DNA is investigated using a simple worm like chain model. In the limit of small force there are large conformational fluctuations which are treated using a self-consistent variational approach. For small values of the external force f, we find the extension scales as where rD is the Debye screening length. In the limit of large force the electrostatic effects can be accounted for within the semiflexible chain model of DNA by assuming that only small excursions from rod-like conformations are possible. In this regime the extension approaches the contour length as where f is the magnitude of the external force. The theory is used to analyze experiments that have measured the extension of double-stranded DNA subject to tension at various salt concentrations. The theory reproduces nearly quantitatively the elastic response of DNA at small and large values of f and for all concentration of the monovalent counterions. The limitations of the theory are also pointed out.
PACS: 36.20.-r – Macromolecules and polymer molecules / 61.25.Hq – Macromolecular and polymer solutions; polymer melts; swelling / 87.15.By – Structure and bonding
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 1999