<i>50th Anniversary Perspective</i>: A Perspective on Polyelectrolyte Solutions

Muthukumar, M.

doi:10.1021/acs.macromol.7b01929

Cited by 387 publications

(462 citation statements)

References 178 publications

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“…Thus, the charge density parameter l b / a end ≥1 allows the CC. Dipole‐dipole interactions of ion pairs formed by condensed counterion with the opposite charge on the chain can be quite strong compared to k B T. The energy of dipole‐dipole interactions ( U dipole‐dipole ) of these ion pairs can be approximated by the energy of two freely rotating dipoles p 1 and p 2 of unit charge separated by the distance r :

\frac{U_{dipole - dipole}}{k_{B} T} = - \frac{l_{b}^{2} p_{1}^{2} p_{2}^{2}}{3 r^{6}} e^{- 2 normalκ r} ([], 1 + 2 normalκ r + \frac{5}{3} {(κ r)}^{2} + \frac{2}{3} {(κ r)}^{3} + \frac{1}{6} {(κ r)}^{4})

where κ −1 is the Debay length (the screening length of electrostatic interactions).…”

Section: Resultsmentioning

confidence: 99%

“…Thus, the charge density parameter l b /a end ≥1 allows the CC. Dipoledipole interactions of ion pairs formed by condensed counterion with the opposite charge on the chain can be quite strong compared to k B T. [20] The energy of dipole-dipole interactions (U dipole-dipole ) of these ion pairs can be approximated by the energy of two freely rotating dipoles p 1 and p 2 of unit charge separated by the distance r [20] : polyelectrolytes with hydrophobic associative groups, [32] CAC decreases with the number of stickers. Although the association in κCGs was supported by other kinds of stickers (the dipoles of reducing endgroups capping the condensed counterions and helical iota-carrageenan blocks), we observed the same tendency.…”

Section: Two Kinds Of Associative Groupsmentioning

confidence: 99%

“…Nevertheless, the association started with increasing concentration, as revealed by appearance of the second slow DLS mode. The slow mode was assigned to the clustering ordinarily observed in highly charged polyelectrolytes in which the attractive interactions between polyions are mediated by condensed counterions . The characterization of hydrolyzed κ‐carrageenans was accomplished by traditional capillary viscometry.…”

Section: Introductionmentioning

confidence: 99%

“…The slow mode was assigned to the clustering ordinarily observed in highly charged polyelectrolytes in which the attractive interactions between polyions are mediated by condensed counterions. [20] The characterization of hydrolyzed κ-carrageenans was accomplished by traditional capillary viscometry. We applied also FT-IR-spectrometry and electrophoretic DLS to study the chemical structure changes during the peeling.…”

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confidence: 99%

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Association of κ‐carrageenan subjected to deep alkaline hydrolysis

et al. 2018

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κ‐carrageenan is a linear sulfated anionic gelling polysaccharide obtained from red seaweed algae by an alkaline hydrolysis. We applied static and dynamic light scattering (DLS), capillary viscometry, FT‐IR, and electrophoretic DLS to gain insight into the effect of deep alkaline hydrolysis (95 °C, pH = 10 during Th = 60, 75, and 90 min) on κ‐carrageenan macromolecules in a coil conformation. As DLS of coil‐like κ‐carrageenans is usually complicated by spurious permanent aggregates, the alkaline hydrolysis of κ‐carrageenans has not been studied by DLS. By applying a double‐dialysis procedure (first against water, then against 0.1 M NaCl), we succeeded in obtaining dilute solutions of coil‐like κ‐carrageenans with unimodal DLS distributions. Association that started with increasing concentration was attributed to attractive dipole‐dipole interactions between ion‐pairs formed by condensed counter‐ions in the vicinity of carboxyl groups of the reducing ends. The second type of stickers resulted from the compositional heterogeneity of κ‐carrageenan, namely, from the traces of ι‐carrageenan blocks which amount increased with hydrolysis. With increasing Th we observed both the progressive decrease of molecular mass and the growth of association. Lowering the temperature and increasing concentration during lyophilization strengthened the intermolecular junctions, leading to the formation of permanent aggregates.

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\frac{U_{dipole - dipole}}{k_{B} T} = - \frac{l_{b}^{2} p_{1}^{2} p_{2}^{2}}{3 r^{6}} e^{- 2 normalκ r} ([], 1 + 2 normalκ r + \frac{5}{3} {(κ r)}^{2} + \frac{2}{3} {(κ r)}^{3} + \frac{1}{6} {(κ r)}^{4})

where κ −1 is the Debay length (the screening length of electrostatic interactions).…”

Section: Resultsmentioning

confidence: 99%

Section: Two Kinds Of Associative Groupsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Association of κ‐carrageenan subjected to deep alkaline hydrolysis

et al. 2018

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“…These numbers are directly related to the magnitude of a molecule's electrostatic field and can thus be used to infer the strength of electrostatics interactions (see "Strategy to measure the electrostatics of nucleosomes"). [22][23][24][25][28][29][30][31][32][33][34][35][36] In this work, we use ion counting to determine the number of ions associated with free double-stranded (ds)DNA and with nucleosomes, providing a quantitative comparison of their net electrostatic fields. We find that canonical nucleosomes preferentially attract cations ('counterions') over anions and do so to an extent similar to non-nucleosomal DNA, confirming Model II prediction of a strong negative potential around nucleosomes.…”

Section: Introductionmentioning

confidence: 99%

Ion counting demonstrates a high electrostatic potential of the nucleosome

Gębala¹,

Johnson

Narlikar

et al. 2019

Preprint

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The fundamental unit of chromatin is the nucleosome, which comprises of DNA wrapped around a histone protein octamer. The association of positively charged histone proteins with negatively charged DNA is intuitively thought to attenuate the electrostatic repulsion of DNA, resulting in a weakly charged nucleosome complex.In contrast, theoretical and computational studies suggest that the nucleosome retains a strong, negative electrostatic field. Despite their fundamental implications for chromatin organization and function, these opposing models have not been experimentally tested. Herein, we directly measure nucleosome electrostatics and find that while nucleosome formation reduces the complex charge by half, the nucleosome nevertheless maintains a strong negative electrostatic field. Further, our results show that the wrapping of DNA around a histone octamer increases the propensity of the DNA to make interactions with multivalent cations like Mg 2+ . These findings indicate that presentation of DNA on a nucleosome may more strongly attract positively-charged DNA binding proteins. Our studies highlight the importance of considering the polyelectrolyte nature of the nucleosome and its impact on processes ranging from factor binding to DNA compaction.

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Macromolecular Modeling

Simmons¹

2022

Macromolecular Engineering

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Polymer molecular modeling is particularly challenging due to the role of multibody effects and the large range of time and length scales involved. Mean‐field descriptions of many polymer phenomena are well established; however, they typically do not provide for quantitative prediction and often miss or do not address important qualitative features of polymer behavior. Given the massive chemical space available, improvements in modeling and prediction are crucial to polymer design. To overcome these challenges, modelers increasingly employ hybrid approaches in which multiple complementary theoretical frameworks are applied to the same molecular model. This article provides a tutorial introduction to this area. We discuss a conceptual taxonomy for classifying and understanding modeling approaches, survey key theoretical frameworks and molecular models, and discuss factors based on which one might choose among them. Particular attention is given to molecular dynamics (MD) simulations as a versatile baseline capability, with a focus on the aspects of particular challenge and importance in treating polymers. Finally, we review examples of hybrid approaches that combine these methods to treat polymer phenomena that are challenging to treat via any single method alone, including both combination of multiple physics‐based theoretical frameworks and combination of physics‐based modeling with data‐based and optimization methods.

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50th Anniversary Perspective: A Perspective on Polyelectrolyte Solutions

Cited by 387 publications

References 178 publications

Association of κ‐carrageenan subjected to deep alkaline hydrolysis

Association of κ‐carrageenan subjected to deep alkaline hydrolysis

Ion counting demonstrates a high electrostatic potential of the nucleosome

Macromolecular Modeling

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