The electrostatic persistence length of polymers beyond the OSF limit

Abstract

Abstract. We use large scale Monte Carlo simulations to test scaling theories for the electrostatic persistence length le of isolated, uniformly charged polymers with Debye-Hückel intrachain interactions in the limit where the screening length κ −1 exceeds the intrinsic persistence length of the chains. Our simulations cover a significantly larger part of the parameter space than previous studies. We observe no significant deviations from the prediction le ∝ κ −2 by Khokhlov and Khachaturian which is based on applying the Odijk-Skolnick-Fixman theory to the stretched de Gennes-Pincus-Velasco-Brochard polyelectrolyte blob chain. A linear or sublinear dependence of the persistence length on the screening length can be ruled out. We argue that previous numerical results pointing into this direction are probably due to a combination of excluded volume and finite chain length effects. The paper emphasizes the role of scaling arguments in the development of useful representations for experimental and simulation data.PACS. 6 4.60.-i -3 6.20.-r -8 7.15.By

Perspective: Single polymer mechanics across the force regimes

“…58 This picture, formally equivalent to the Barrat-Joanny model, 58 was motivated by a variety of simulation results that indicated flexible chains are not well-described by a single persistence length over all scales, but rather by a dual-regime picture in which the chain has some short-length-scale flexibility that is relatively unaffected by electrostatics, followed by a long-length-scale structure that is stiffened by electrostatic repulsion. [59][60][61][62][63] The crossover between these scales appears, in simulations, to vary linearly with Debye length, 63 in agreement with the single-chain elasticity experiments on ssNAs. 19,22 Further confirmation of this picture arises from the anomalous elasticity of ssNAs in the high force ( f > k B T/ℓ) regime, which do not follow the WLC prediction, Eq.…”

“…These include the electrostatic behavior of chains whose non-electrostatic stiffness lies between that of single-and double-stranded DNA, and the behavior of weakly charged chains, about which theoretical work has already posited a range of structural regimes. 59,70 Finally, single-molecule methods are not limited to determining charged polymer structure; other complex structures, e.g., including branched or bottle brush configurations, are likely to be productive targets with these methods. …”

Electrostatic interactions in biological DNA-related systems

“…NCPs are known to be stable only in a limited range of [simple salt] close to B0.1 M. 289 At smaller [salt] the DNA becomes stiffer due to ES contribution to its bending persistence length, 290,291 see also ref. [292][293][294][295][296]. At high [salt], on the other hand, the ES DNA-(histone core) affinity is attenuated by screening.…”

Probing structural heterogeneities and fluctuations of nucleic acids and denatured proteins

“…In theoretical models, l P is divided into intrinsic l P 0 and electrostatic l P el components, l P ϭ l P 0 ϩ l P el . In Odijk-Skolnick-Fixman theory for charged wormlike chains (2) and some extensions to flexible polymers (34,35), l P el ϰ I Ϫ1 , where I is the ionic strength (dotted lines). Others predict l P el ϰ I Ϫ1/2 (solid lines) (36,37).…”