Characterisation of aqueous interfaces with different hydrophobicities by molecular dynamics

Buuren, Aldert R. van; Marrink, Siewert J.; Berendsen, Herman J. C.

doi:10.1016/0927-7757(95)03227-5

Cited by 23 publications

(20 citation statements)

References 42 publications

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“…Molecular dynamics studies of a water/vapor interface yielded Φ < 0 for the TIP3P water model [40] and Φ > 0 for the TIP4P [39] or the SPC/E water model [41]. A molecular dynamics study of a water/decane interface yielded Φ ≈ +0.4 V for the SPC water model [12]. Recent molecular dynamics studies of a water/hexane interface using a polarizable water model yielded Φ ≈ +0.1 V for a fixed-charge hexane force field and Φ ≈ +0.4 V for a polarizable hexane force field [42].…”

Section: Electrostatic Potential In Oil Phase Is Positivementioning

confidence: 96%

“…Heptane droplets of radius 1.5 nm (system S), 4.7 nm (system M), or 8.2 nm (system L), a slab (system P), or two hydrophobic walls (system W) were simulated under periodic boundary conditions. The droplet radius in system S was chosen to be somewhat larger than the width of a water/oil interface suggested from previous simulations [12]. The droplet size in system L was chosen to maximize size while keeping the computations feasible.…”

Section: Simulation Setupmentioning

confidence: 99%

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Electrophoretic mobility does not always reflect the charge on an oil droplet

Knecht

Risselada

Mark

et al. 2008

Journal of Colloid and Interface Science

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Electrophoresis is widely used to determine the electrostatic potential of colloidal particles. Oil droplets in pure water show negative or positive electrophoretic mobilities depending on the pH. This is commonly attributed to the adsorption of hydroxyl or hydronium ions, resulting in a negative or positive surface charge, respectively. This explanation, however, is not in agreement with the difference in isoelectric point and point of zero charge observed in experiment. Here we present molecular dynamics simulations of oil droplets in water in the presence of an external electric field but in the absence of any ions. The simulations reproduce the negative sign and the order of magnitude of the oil droplet mobilities at the point of zero charge in experiment. The electrostatic potential in the oil with respect to the water phase, induced by anisotropic dipole orientation in the interface, is positive. Our results suggest that electrophoretic mobility does not always reflect the net charge or electrostatic potential of a suspended liquid droplet and, thus, the interpretation of electrophoresis in terms of purely continuum effects may need to be reevaluated.

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Section: Electrostatic Potential In Oil Phase Is Positivementioning

confidence: 96%

Section: Simulation Setupmentioning

confidence: 99%

Electrophoretic mobility does not always reflect the charge on an oil droplet

Knecht

Risselada

Mark

et al. 2008

Journal of Colloid and Interface Science

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“…The HG dipole charges and the surrounding dipole fields preferentially orient and partially immobilize the water molecules up to a distance of 0.5 nm from the membrane surface [Frischleder and Peinel, 1982;Flewelling and Hubbell, 1986;Buuren et al, 1995;Tielemann et al, 1997]. On average, there are 10-15 water molecules, ''bound'' to one lipid HG (Fig.…”

Section: Models Membrane Propertiesmentioning

confidence: 96%

“…Such membrane models have been successfully applied in molecular dynamics simulations to study the ion translocation through the lipid phase of the membrane [Tielemann et al, 1997] as well as to determine the electrostatic transmembrane potential profile [Heinrich et al, 1982;Buuren et al, 1995;Lin et al, 2002]. To our knowledge, only layered membrane models differentiating between lipid and bound water layers have been applied to model EMF effects [Liu and Cleary, 1995;Sebastian et al, 2001].…”

Section: Introductionmentioning

confidence: 99%

“…The aliphatic chains of the lipids form a hydrophobic membrane core confined by the thin hydrophilic headgroup (HG) regions [Tielemann et al, 1997]. Water in the vicinity of membranes is strongly immobilized by the dipole charges of the HGs [Frischleder and Peinel, 1982;Flewelling and Hubbell, 1986;Buuren et al, 1995]. This bound water (BW) has properties that are significantly different from that of free water and it can therefore be considered as part of the membrane [Tielemann et al, 1997].…”

Section: Introductionmentioning

confidence: 99%

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The influence of the molecular structure of lipid membranes on the electric field distribution and energy absorption

Simeonova

Gimsa

2006

Bioelectromagnetics

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We consider the influence of the molecular structure of phospholipid membranes on their dielectric properties in the radio frequency range. Membranes have a stratified dielectric structure on the submolecular level, with the lipid chains forming a central hydrophobic layer enclosed by the polar headgroups (HGs) and bound water layers. In our numerical model, isotropic permittivities of 2.2 and 48.8 were assigned to the lipid chain and bound water layers, respectively. The HG region was assumed to possess an anisotropic static permittivity with 142.2 and 30.2 in the tangential and normal directions, respectively. The permittivities of the HG and bound water regions have been assumed to disperse at frequencies around 51 and 345 MHz to become 2.2 and 1.8, respectively, in both the normal and tangential directions. Electric field distribution and absorption were calculated for phospholipid vesicles with 75 nm radius as an example. Significant absorption has been obtained in the HG and bound water regions. Averaging the membrane absorption over the layers resulted in a decreased absorption below 1 GHz but a more than 10-fold increase above 1 GHz, compared to a model with a homogeneous membrane of averaged properties. We propose single particle dielectric spectroscopy by AC electrokinetics at low-bulk medium conductivities for an experimental verification of our model.

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Simulations of Liquid-Liquid Interfaces: A Key Border in Supramolecular Chemistry

Berny¹,

Muzet²,

Troxler³

et al. 1999

Supramolecular Science: Where It Is and Where It Is Going

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Characterisation of aqueous interfaces with different hydrophobicities by molecular dynamics

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Cited by 23 publications

References 42 publications

Electrophoretic mobility does not always reflect the charge on an oil droplet

Electrophoretic mobility does not always reflect the charge on an oil droplet

The influence of the molecular structure of lipid membranes on the electric field distribution and energy absorption

Simulations of Liquid-Liquid Interfaces: A Key Border in Supramolecular Chemistry

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