Scale-dependent electrostatic stiffening in biopolymers

Alexander Gubarev, Jan Michael Y. Carrillo, Andrey V. Dobrynin

Research output: Contribution to journalArticlepeer-review

31 Scopus citations

Abstract

Using a combination of the molecular dynamics simulations and theoretical calculations, we have demonstrated that bending rigidity of biological polyelectrolytes (semiflexible charged polymers) is scale-dependent. A bond-bond correlation function describing a chain's orientational memory can be approximated by a sum of two exponential functions manifesting the existence of the two characteristic length scales. One describes the chain's bending rigidity at the distances along the polymer backbone shorter than the Debye screening length, whereas another controls the long-scale chain's orientational correlations. The shortlength scale bending rigidity is proportional to the Debye screening length at high salt concentrations and shows a weak logarithmic dependence on salt concentration when the Debye screening length exceeds a crossover value of K-1cr ∝ (lBα 2/lP)-1/2 (where lB is the Bjerrum length, a is the fraction of ionized groups, and /p is a bare persistence length). The long-scale chain's bending rigidity has a well-known Odijk-Skolnick-Fixman form with a quadratic dependence on the Debye radius. Simulation results and a theoretical model demonstrate good qualitative agreement.

Original languageEnglish
Pages (from-to)5851-5860
Number of pages10
JournalMacromolecules
Volume42
Issue number15
DOIs
StatePublished - Aug 11 2009
Externally publishedYes

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