Role of Repulsive Forces in Determining the Equilibrium Structure of Simple Liquids

Weeks, John D.; Chandler, David; Andersen, Hans Christian

doi:10.1063/1.1674820

Cited by 4,836 publications

(3,254 citation statements)

References 28 publications

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“…The headgroups interact with each other via a short-range repulsive Weeks-Chandler-Anderson (WCA) potential 62 and the screened Coulomb potential. The WCA interaction accounts for the finite size of the headgroup.…”

Section: Simulation Model and Methodsmentioning

confidence: 99%

Electrostatic Screening and Charge Correlation Effects in Micellization of Ionic Surfactants

et al. 2009

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We have used atomistic simulations to study the role of electrostatic screening and charge correlation effects in self-assembly processes of ionic surfactants into micelles. Specifically, we employed grand canonical Monte Carlo simulations to investigate the critical micelle concentration (cmc), aggregation number, and micellar shape in the presence of explicit sodium chloride (NaCl). The two systems investigated are cationic dodecyltrimethylammonium chloride (DTAC) and anionic sodium dodecyl sulfate (SDS) surfactants. Our explicit-salt results, obtained from a previously developed potential model with no further adjustment of its parameters, are in good agreement with experimental data for structural and thermodynamic micellar properties. We illustrate the importance of ion correlation effects by comparing these results with a Yukawa-type surfactant model that incorporates electrostatic screening implicitly. While the effect of salt on the cmc is well-reproduced even with the implicit Yukawa model, the aggregate size predictions deviate significantly from experimental observations at low salt concentrations. We attribute this discrepancy to the neglect of ion correlations in the implicit-salt model. At higher salt concentrations, we find reasonable agreement of the Yukawa model with experimental data. The crossover from low to high salt concentrations is reached when the electrostatic screening length becomes comparable to the headgroup size.

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Section: Simulation Model and Methodsmentioning

confidence: 99%

Electrostatic Screening and Charge Correlation Effects in Micellization of Ionic Surfactants

et al. 2009

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“…This decomposition is somewhat arbitrary, but it turns out that the final results are extremely insensitive to how this split is made. We choose to use the Weeks-ChandlerAndersen approach 48 where β has its usual meaning of 1/k B T, where k B is Boltzmann's constant and T is temperature. This has dimensions of volume and plays the role of an equilibrium constant.…”

Section: Free Energy Of Associationmentioning

confidence: 99%

Thermodynamics of the self-assembly of non-ionic chromonic molecules using atomistic simulations. The case of TP6EO2M in aqueous solution

et al. 2015

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(2015) 'Thermodynamics of the self-assembly of non-ionic chromonic molecules using atomistic simulations.The case of TP6EO2M in aqueous solution.', Soft matter., 11 (4). pp. 680-691. Further information on publisher's website:http://dx.doi.org/10.1039/C4SM02275KPublisher's copyright statement:Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. ABSTRACTAtomistic molecular dynamic simulations have been performed for the non-ionic chromonic liquid crystal 2,3,6,7,10,11-hexa-(1,4,7-trioxa-octyl)-triphenylene (TP6EO2M) in aqueous solution. TP6EO2M molecules consist of a central poly-aromatic core (a triphenylene ring) functionalized by six hydrophilic ethyleneoxy (EO) chains, and have a strong tendency to aggregate face-to-face into stacks even in very dilute solution. We have studied self-assembly of the molecules in the low concentration range corresponding to an isotropic solution of aggregates, using two force fields GAFF and OPLS. Our results reveal that the GAFF force field, even though it was successfully used previously for modelling of ionic chromonics, overestimates the attraction of TP6EO2M molecules in water. This results in an aggregation free energy which is too high, a reduced hydration of EO chains and, therefore, molecular self-assembly into compact disordered clusters instead of stacks. In contrast, use of the OPLS force field, leads to self-assembly into ordered stacks in agreement with earlier experimental studies of triphenylene-based chromonics. The free energy of association follows a "quasi-isodesmic" pattern, where the binding free energy of two molecules to form a dimer is of the order of 3 RT larger than the corresponding energy of addition of a molecule into a stack. The obtained value for the binding free energy, ∆ agg G 0 = -12 RT, is found to be in line with the published values for typical ionic chromonics (-7 to -12 RT), and agrees reasonably well with the experimental results for this system. The calculated interlayer distance between the molecules in a stack is 0.37 nm, which is at the top of the range found for typical chromonics (0.33-0.37 nm). We suggest that the relatively large layer spacing can be attributed to the repulsion between EO side chains.2

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“…Following the Weeks-Chandler-Andersen (WCA) theory (Weeks 1971), we decompose U int; X into the repulsive and attractive parts. The crowding free energy, ΔF crowd X f ð Þ, can thus be divided into two separable contributions as,…”

Section: Thermodynamics Of Protein-protein Interactions In a Crowder mentioning

confidence: 99%

Protein–protein interactions in a crowded environment

2013

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Protein-protein interactions are important in many essential biological functions, such as transcription, translation, and signal transduction. Much progress has been made in understanding protein-protein association in dilute solution via experimentation and simulation. Cells, however, contain various macromolecules, such as DNA, RNA, proteins, among many others, and a myriad of non-specific interactions (usually weak) are present between these cellular constituents. In this review article, we describe the important developments in recent years that have furthered our understanding and even allowed prediction of the consequences of macromolecular crowding on protein-protein interactions. We outline the development of our crowding theory that can predict the change in binding free energy due to crowding quantitatively for both repulsive and attractive protein-crowder interactions. One of the most important findings from our recent work is that weak attractive interactions between crowders and proteins can actually destabilize protein complex formation as opposed to the commonly assumed stabilizing effect predicted based on traditional crowding theories that only account for the entropicexcluded volume effects. We also discuss the implications of macromolecular crowding on the population of encounter versus specific native complex.

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Role of Repulsive Forces in Determining the Equilibrium Structure of Simple Liquids

Cited by 4,836 publications

References 28 publications

Electrostatic Screening and Charge Correlation Effects in Micellization of Ionic Surfactants

Electrostatic Screening and Charge Correlation Effects in Micellization of Ionic Surfactants

Thermodynamics of the self-assembly of non-ionic chromonic molecules using atomistic simulations. The case of TP6EO2M in aqueous solution

Protein–protein interactions in a crowded environment

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