Evidence of Electrostatic Attraction between Equally Charged Macroions Induced by Divalent Counterions

Hribar, Barbara; Vlachy, Vojko

doi:10.1021/jp970007b

Cited by 80 publications

(56 citation statements)

References 24 publications

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“…The field leading to a smaller increase of Ω M F is thermally excited with a higher probability (7), and such OP dominates over the other one. Which one of the two infinitesimal fields,φ(k) orη(k) dominates, depends on which function,C φφ (k) orC ηη (k), is smaller (see (42)). This, in turn, depends on sign(C +− (k)) (see (43) and (44)).…”

Section: B Dominant Order Parametersmentioning

confidence: 99%

Field theory for size- and charge-asymmetric primitive model of ionic systems: Mean-field stability analysis and pretransitional effects

2007

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The primitive model of ionic systems is investigated within a field-theoretic description for the whole range of size-, λ, and charge, Z, ratios of the two ionic species. Two order parameters (OP) are identified, and their relations to physically relevant quantities are described for various values of λ and Z. Instabilities of the disordered phase associated with the two OP's are determined in the mean-field approximation (MF). In MF a gas-liquid separation occurs for any Z and λ = 1. In addition, an instability with respect to various types of periodic ordering of the two kinds of ions is found. Depending on λ and Z, one or the other transition is metastable in different thermdynamic states. The instabilities found in MF represent weak ordering of the majority of the instantaneous states, and are identified with structural loci associated with pretransitional effects.

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Section: B Dominant Order Parametersmentioning

confidence: 99%

Field theory for size- and charge-asymmetric primitive model of ionic systems: Mean-field stability analysis and pretransitional effects

2007

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“…Very long runs, typically of the order of 100 millions configurations for each macroion separation, were required to obtain good statistical accuracy (within 2-3%). This requirement follows from the fact that we sample the force between a single pair of macroions, unlike the procedure used in previous simulations for systems with many macroions (28,29). At 25°C, we investigated interactions between identical negatively charged macroions (the diameter of macroions M ϭ 20 Å and the charge z M ϭ Ϫ20) in 1:1, 1:2, 2:1, and 2:2 electrolyte solutions at various small-ion concentrations (the diameters of all small ions are 4 Å).…”

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confidence: 99%

Interaction between like-charged colloidal spheres in electrolyte solutions

Bratko

Prausnitz

1998

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

156

161

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How colloidal particles interact with each other is one of the key issues that determines our ability to interpret experimental results for phase transitions in colloidal dispersions and our ability to apply colloid science to various industrial processes. The long-accepted theories for answering this question have been challenged by results from recent experiments. Herein we show from Monte-Carlo simulations that there is a short-range attractive force between identical macroions in electrolyte solutions containing divalent counterions. Complementing some recent and related results by others, we present strong evidence of attraction between a pair of spherical macroions in the presence of added salt ions for the conditions where the interacting macroion pair is not affected by any other macroions that may be in the solution. This attractive force follows from the internal-energy contribution of counterion mediation. Contrary to conventional expectations, for charged macroions in an electrolyte solution, the entropic force is repulsive at most solution conditions because of localization of small ions in the vicinity of macroions. Both Derjaguin-Landau-Verwey-Overbeek theory and Sogami-Ise theory fail to describe the attractive interactions found in our simulations; the former predicts only repulsive interaction and the latter predicts a long-range attraction that is too weak and occurs at macroion separations that are too large. Our simulations provide fundamental ''data'' toward an improved theory for the potential of mean force as required for optimum design of new materials including those containing nanoparticles.The potential of mean force between colloidal particles in electrolyte solutions plays a central role in describing the phase behavior and the kinetics of agglomeration in colloidal dispersions (1, 2). It is of fundamental importance for understanding the properties of inorganic materials (e.g., ceramics composed of nanoparticles), foods such as milk, and solutions of biomacromolecules including globular proteins (3-5). After decades of theoretical and experimental efforts, some aspects of colloidal interactions remain puzzling, in particular the issue of attractive electrostatic forces between like-charged colloidal particles in an electrolyte solution. Experimental evidence for such attraction has been indirect and largely complicated by boundary or polydispersity effects (6-8). Classical theories are not satisfactory because they are based on the mean-field approximation that neglects the effects of excluded volume and Coulombic correlations among small ions. Depending on simplifying assumptions, these theories have led to qualitatively different results. For example, theories based on the Derjaguin-Landau-Verwey-Overbeek (DLVO) approximation describe the electrostatic interaction between macroions of the same charge as screened repulsion (9-10, 12, 13), and others, represented by Sogami-Ise (SI) theory, predict a universal long-range attractive interaction (11,14). Likewise, the possibil...

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“…We see that dimerized proteins are, as result of twice higher charge, distributed at larger distances from each other than monomers. This result is expected for solutions with monovalent counterions but for more highly coupled systems (low dielectric constant and/or multivalent counterions) the situation may be different as shown before by Hribar and Vlachy [30,33,34].…”

Section: Theory Versus Simulationsmentioning

confidence: 64%

Analysis of osmotic pressure data for aqueous protein solutions via a multicomponent model

Druchok

Kalyuzhnyi

Reščič

et al. 2006

The Journal of Chemical Physics

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Аналiз даних для осмотичного тиску водних розчинiв про-теїнiв на основi багатокомпонентної моделi М. Дручок, Ю. Калюжний, Ю. Рещiч, В. Влахi Анотацiя. Проведено дослiдження рiвноваги Донана. Електролiт змодельовано протеїнами у формах мономерiв i димерiв, ко-i кон-трiонами, що представленi зарядженими твердими сферами рiзного розмiру i заряду. Для вивчення властивостей моделi було викорис-тано розв'язок рiвняння Орнштейна-Цернiке у асоцiативних серед-ньосферичному i гiперланцюжковому наближеннях. Для перевiрки теорiї проведено моделювання методом Монте-Карло моделi водного розчину протеїну лiзоциму при 0.1-мольному буферi NaCl. Запропо-новану теорiю було застосовано до опису низки експериментальних даних осмотичного тиску для протеїнiв bovine serum albumin в 0.15-мольному буферi NaCl, human serum albumin в 0.1-мольному фосфа-тному буферi i лiзоциму в сульфатному i фосфатному буферах.Analysis of osmotic pressure data for aqueous protein solutions via a multi-component model M.Druchok, Yu.Kalyuzhnyi, J.Reščič and V.Vlachy Abstract. A Donnan equilibrium for a series of systems is studied. In order to describe the unusually low osmotic pressure in many experiments we assumed protein molecules can form dimers. The model solution contains proteins in monomeric or dimerized forms, co-and counterions, which are modelled as charges spheres. The associative mean spherical and hypernetted chain approximations were applied to this model. In order to test the theory a Monte Carlo simulations were performed for the model mimicking lysozyme solution in 0.1M sodium chloride buffer. Using the theoretical approaches mentioned above we analyzed experimental data for the osmotic pressure of bovine serum albumin in 0.15M sodium chloride, human serum albumin solution in 0.1M phosphate buffer and lysozyme in sulphate and phosphate buffers.

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Evidence of Electrostatic Attraction between Equally Charged Macroions Induced by Divalent Counterions

Cited by 80 publications

References 24 publications

Field theory for size- and charge-asymmetric primitive model of ionic systems: Mean-field stability analysis and pretransitional effects

Field theory for size- and charge-asymmetric primitive model of ionic systems: Mean-field stability analysis and pretransitional effects

Interaction between like-charged colloidal spheres in electrolyte solutions

Analysis of osmotic pressure data for aqueous protein solutions via a multicomponent model

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