TY - JOUR

T1 - Scale-dependent electrostatic stiffening in biopolymers

AU - Gubarev, Alexander

PY - 2009/8/11

Y1 - 2009/8/11

N2 - 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.

AB - 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.

UR - http://www.scopus.com/inward/record.url?scp=68549135359&partnerID=8YFLogxK

U2 - 10.1021/ma9008143

DO - 10.1021/ma9008143

M3 - Article

AN - SCOPUS:68549135359

VL - 42

SP - 5851

EP - 5860

JO - Macromolecules

JF - Macromolecules

SN - 0024-9297

IS - 15

ER -