Effect of electrostatic interaction on the liquid crystal phase transition in solutions of rodlike polyelectrolytes

Stroobants, A.; Lekkerkerker, H. N. W.; Odijk, Theo

doi:10.1021/ma00162a020

Cited by 347 publications

(399 citation statements)

References 22 publications

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“…Such models relied upon a highly salt-dependent charge density (22) inappropriately obtained from an effective-charge DH model (42)(43)(44)(45) valid only in the far field and not suitable for treating interactions between neighboring charges. This charge density was seemingly validated through experiments (20,21), but those studies were not conducted over a broad range of I and thus were not well suited to critically test salt-dependent effects.…”

Section: Discussionmentioning

confidence: 99%

Single-stranded nucleic acid elasticity arises from internal electrostatic tension

Jacobson

McIntosh

Stevens

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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Understanding of the conformational ensemble of flexible polyelectrolytes, such as single-stranded nucleic acids (ssNAs), is complicated by the interplay of chain backbone entropy and saltdependent electrostatic repulsions. Molecular elasticity measurements are sensitive probes of the statistical conformation of polymers and have elucidated ssNA conformation at low force, where electrostatic repulsion leads to a strong excluded volume effect, and at high force, where details of the backbone structure become important. Here, we report measurements of ssDNA and ssRNA elasticity in the intermediate-force regime, corresponding to 5-to 100-pN forces and 50-85% extension. These data are explained by a modified wormlike chain model incorporating an internal electrostatic tension. Fits to the elastic data show that the internal tension decreases with salt, from >5 pN under 5 mM ionic strength to near zero at 1 M. This decrease is quantitatively described by an analytical model of electrostatic screening that ascribes to the polymer an effective charge density that is independent of force and salt. Our results thus connect microscopic chain physics to elasticity and structure at intermediate scales and provide a framework for understanding flexible polyelectrolyte elasticity across a broad range of relative extensions.single-stranded nucleic acids | flexible polyelectrolytes | force spectroscopy | electrostatics S ingle-stranded nucleic acids (ssNAs) occur in many biological processes, such as RNA folding (1, 2) and DNA replication (3-5), generally in disordered conformations that fluctuate between various structures. These fluctuations create a significant entropic elasticity; thus, direct measurements of molecular elasticity (extension, X , as a function of applied force, fapp) constitute a powerful tool for studying the ssNA structural ensemble (6). In particular, measurements at a particular fapp are sensitive to the conformation within the corresponding tensile length, kB T /fapp (to within a scaling factor), where kB T is the thermal energy (7).ssNA structure-and that of flexible polyelectrolytes more generally-is complicated by the strong negative charge of the molecule. Multiple electrostatic and structural length scales share a similar magnitude (roughly 1 nm), disallowing models that consider only electrostatics or only backbone structure. In an uncharged flexible chain, the key structural scale is the persistence length, lp, defining the distance beyond which thermal fluctuations strongly bend the polymer. Electrostatic interactions introduce several competing length scales: the distance, b, between charged phosphates along the ssNA backbone; the distance over which electrostatic fields are screened in salty solution (the Debye length, κ −1 ); and the distance at which interactions between elementary charges in water have energy kB T (the Bjerrum length, lB ).Prior studies have elucidated ssNA elastic behavior in the lowand high-force limits. At low forces, corresponding to tensile lengths larger than κ −1 (i....

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Section: Discussionmentioning

confidence: 99%

Single-stranded nucleic acid elasticity arises from internal electrostatic tension

Jacobson

McIntosh

Stevens

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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“…Onsager (1949) already indicated that the effect of the electrostatic interaction will be equivalent to an increase of the effective diameter. Many years later Stroobants et al (1986) noted that this is not the only effect of the electrostatic interaction. The electrostatic repulsion depends on orientation and thus the effect of the electrostatic repulsion will be different in the isotropic phase from that in the nematic phase.…”

Section: Charged Rodsmentioning

confidence: 99%

“…The electrostatic repulsion depends on orientation and thus the effect of the electrostatic repulsion will be different in the isotropic phase from that in the nematic phase. In the remainder of this section we closely follow the treatment for charged rods given in Stroobants et al (1986).…”

Section: Charged Rodsmentioning

confidence: 99%

“…I n addition to the larger effective diameter the electrostatic interaction shows up in the extra term which is called the twisting effect as it originates from the factor (sin y)-l in equation (35). The relative importance of this effect is determined by the parameter Stroobants et al (1986) determined the isotropic-nematic phase transition from the free energy (37). As the scaled concentration now is based on the larger effective diameter the phase transition is shifted to lower particle number densities.…”

Section: Charged Rodsmentioning

confidence: 99%

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Lyotropic colloidal and macromolecular liquid crystals

Lekkerkerker

Vroege

1993

Phil. Trans. R. Soc. Lond. A

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We review the theory of the isotropic—nematic phase transition for solutions of thin hard rods and semi-flexible chain molecules along with the extensions to polydisperse systems and soft interactions. The occurrence of more highly ordered liquid crystal phases (smectic, columnar) in concentrated solutions of colloids and macromolecules is discussed briefly. Experimental results for a number of carefully studied uncharged and charged colloids and macromolecules are compared to theoretical results.

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“…26 Another important aspect that needs to consider is the effects of charge and ionic strength that biopolymers carry in aqueous solution. [27][28][29] From a theoretical point of view, electrostatic interactions can cause the rods to twist away from the parallel configuration with respect to each other and increase the hardcore diameter to a larger effective one, while the persistence length increases as well. Nevertheless, the viscoelastic properties of LCP's have been studied quantitatively in considerable detail over the recent years.…”

Section: Introductionmentioning

confidence: 99%

Isotropic−Nematic Phase Equilibrium and Phase Separation of κ-Carrageenan in Aqueous Salt Solution: Experimental and Theoretical Approaches

Chronakis

Ramzi

2002

Biomacromolecules

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The behavior of chiral-nematic and isotropic phases of helical κ-carrageenan in aqueous solution of sodium iodide was compared with that of the anisotropic biphasic phase that contains both these phases. On the basis of birefringence, rheology, chemical analysis, average molecular weight, and polydispersity index measurements, we derived a number of characteristic differences as well as similarities between these phases, over a range of polysaccharide concentrations obtained by the dilution of each phase. For example, we assessed the critical concentration of an isotropic-anisotropic transition (C i ), the temperature of the anisotropic-isotropic phase shift during thermal heating-cooling cycles, and the viscosity changes due to the phase shift and due to the diminishing of the helical conformation. We also demonstrated how the different phases and their dilutions behave under the effect of shear and frequency of oscillation and how the viscoelastic properties vary in each phase and discussed the isotropic and anisotropic liquid crystal controlling behavior mechanisms. From a theoretical point of view, we propose to combine the wormlike chain model for semiflexible polyelectrolytes interacting via both hard-core and electrostatic repulsion to assess the concentration of isotropic-nematic transition, to assess the coexistence concentration range, and to determine the effects of charge by applying the effective diameter and a twisting effect. IntroductionThe carrageenans are linear, sulfated polygalactans extracted from various species of marine red algae, (i.e., Eucheuma cottoni, Eucheuma spinosum, Gigartina acicularis). 1,2 The primary structure is based on a repeating disaccharide sequence of 1,3-linked -D-galactopyranose and 1,4-linked 3,6-anhydro-D-galactopyranose residues. κ-and ι-carrageenan are the two best known gelling varieties.Rigid and semirigid macromolecules can form gels, but there is also a possibility to form ordered phases (nematic, chiral nematic, smectic, hexatic) or both gels and liquid crystalline phases. 3 The liquid crystalline phase is caused by restrictions on rotation, which in turn are caused by volume exclusion for the polymers of high axial ratios. Most experimental investigations on κ-carrageenan (KC) have dealt with conditions where gel formation or aggregations of the helices occur, therefore preventing the development of longrange liquid crystalline order. However, binding of iodide to the (negatively charged) KC helix increases the charge density, thus preventing aggregation and further gelation of the helices. 4,5 In fact, this was demonstrated for sodium iodide concentration of 0.1 M for polymer concentrations up to about 1 g/L. For higher values of sodium iodide concentration, aggregation does indeed take place, nevertheless, at a reduced extent. 6 The binding of iodide explains why the KC solutions require sodium iodide as a solvent to give a nematic liquid crystalline phase. 4 These solutions show a macroscopic phase separation into one anisotropic bottom phase and one isot...

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Effect of electrostatic interaction on the liquid crystal phase transition in solutions of rodlike polyelectrolytes

Cited by 347 publications

References 22 publications

Single-stranded nucleic acid elasticity arises from internal electrostatic tension

Single-stranded nucleic acid elasticity arises from internal electrostatic tension

Lyotropic colloidal and macromolecular liquid crystals

Isotropic−Nematic Phase Equilibrium and Phase Separation of κ-Carrageenan in Aqueous Salt Solution: Experimental and Theoretical Approaches

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