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Carsten Peterson

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The electrostatic persistence length calculated from Monte Carlo, variational and perturbation methods

Författare

  • Magnus Ullner
  • Bo Jönsson
  • Carsten Peterson
  • Ola Sommelius
  • Bo Söderberg

Summary, in English

Monte Carlo simulations and variational calculations using a Gaussian ansatz are applied to a model consisting of a flexible linear polyelectrolyte chain as well as to an intrinsically stiff chain with up to 1000 charged monomers. Addition of salt is treated implicitly through a screened Coulomb potential for the electrostatic interactions. For the flexible model the electrostatic persistence length shows roughly three regimes in its dependence on the Debye-Hückel screening length, κ-1. As long as the salt content is low and κ-1 is longer than the end-to-end distance, the electrostatic persistence length varies only slowly with κ-1. Decreasing the screening length, a controversial region is entered. We find that the electrostatic persistence length scales as √ξp/κ, in agreement with experiment on flexible polyelectrolytes, where ξp is a strength parameter measuring the electrostatic interactions within the polyelectrolyte. For screening lengths much shorter than the bond length, the κ-1 dependence becomes quadratic in the variational calculation. The simulations suffer from numerical problems in this regime, but seem to give a relationship half-way between linear and quadratic. A low temperature expansion only reproduces the first regime and a high temperature expansion, which treats the electrostatic interactions as a perturbation to a Gaussian chain, gives a quadratic dependence on the Debye length. For a sufficiently stiff chain, the persistence length varies quadratically with κ-1 in agreement with earlier theories.

Avdelning/ar

  • Biofysikalisk kemi
  • Computational Biology and Biological Physics

Publiceringsår

1997-07-22

Språk

Engelska

Sidor

1279-1287

Publikation/Tidskrift/Serie

Journal of Chemical Physics

Volym

107

Issue

4

Dokumenttyp

Artikel i tidskrift

Förlag

American Institute of Physics (AIP)

Aktiv

Published

ISBN/ISSN/Övrigt

  • ISSN: 0021-9606