Water orientation at hydrophobic interfaces

Strazdaitė, Simona; Versluis, Jan; Bakker, Huib J.

doi:10.1063/1.4929905

Cited by 64 publications

(58 citation statements)

References 27 publications

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“…Bilayers from (i) phospholipids with or without conventional headgroups (like ethanolamine, choline, or glycerol headgroups) or (ii) lipids that do not contain the anionic phosphate moiety, have similar dipole potentials 32 suggesting that charged moieties are not required to orient water dipoles. This notion is supported by reports about a net orientation of water molecules at the interface to alkene 33 or to other hydrophobic interfaces 34 . It is also in line with the finding that titratable residues are not required for interfacial proton migration 7 .…”

Section: Discussionmentioning

confidence: 64%

Origin of proton affinity to membrane/water interfaces

Weichselbaum

Österbauer

Knyazev

et al. 2017

Sci Rep

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Proton diffusion along biological membranes is vitally important for cellular energetics. Here we extended previous time-resolved fluorescence measurements to study the time and temperature dependence of surface proton transport. We determined the Gibbs activation energy barrier ΔG ‡ r that opposes proton surface-to-bulk release from Arrhenius plots of (i) protons’ surface diffusion constant and (ii) the rate coefficient for proton surface-to-bulk release. The large size of ΔG ‡ r disproves that quasi-equilibrium exists in our experiments between protons in the near-membrane layers and in the aqueous bulk. Instead, non-equilibrium kinetics describes the proton travel between the site of its photo-release and its arrival at a distant membrane patch at different temperatures. ΔG ‡ r contains only a minor enthalpic contribution that roughly corresponds to the breakage of a single hydrogen bond. Thus, our experiments reveal an entropic trap that ensures channeling of highly mobile protons along the membrane interface in the absence of potent acceptors.

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Section: Discussionmentioning

confidence: 64%

Origin of proton affinity to membrane/water interfaces

Weichselbaum

Österbauer

Knyazev

et al. 2017

Sci Rep

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“…The experimental ζ-potential [3] has the sign opposite to that calculated for the Kihara solutes. The reason is the positive sign of p 1 in the Kihara-water interface, while negative p 1 values have been recently reported for the oil-water interface [10,27]. The access to water orientation in the interface is experimentally provided by heterodyne-detected vibrational sum-frequency generation (VSFG) spectroscopy through the imaginary part of the VSFG signal Imχ (2) [27,28].…”

Section: Computer Simulationsmentioning

confidence: 99%

“…We derive a relation between the effective mobility (electrokinetic) charge and the interfacial structure of the water dipoles represented by the first-order orientational order parameter of the interface. This parameter is in principle accessible by surface-sensitive spectroscopies [24,25,27,28] and by equilibrium computer simulations of solutions [29,30].…”

Section: Introductionmentioning

confidence: 99%

Mobility of nanometer-size solutes in water driven by electric field

Dinpajooh

Matyushov

2016

Physica A: Statistical Mechanics and its Applications

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We investigate the mobility of nanometer-size solutes in water in a uniform external electric field. General arguments are presented to show that a closed surface cutting a volume from a polar liquid will carry an effective non-zero surface charge density when preferential orientation of dipoles exists in the interface. This effective charge will experience a non-vanishing drag in an external electric field even in the absence of free charge carriers. Numerical simulations of model solutes are used to estimate the magnitude of the surface charge density. We find it to be comparable to the values typically reported from the mobility measurements. Hydrated ions can potentially carry a significant excess of the effective charge due to over-polarization of the interface. As a result, the electrokinetic charge can significantly deviate from the physical charge of free charge carriers. We propose to test the model by manipulating the polarizability of hydrated semiconductor nanoparticles with light. The inversion of the mobility direction can be achieved by photoexcitation, which increases the nanoparticle polarizability and leads to an inversion of the dipolar orientations of water molecules in the interface.

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“…X-ray absorption spectroscopy and xray Raman scattering demonstrated that water, consists of structures with two strong H-bonds, one donating and one accepting, thus promoting formation of chain-like structures [22][23][24]. There is much theoretical and experimental evidence that water molecules are strongly oriented in the vicinity of hydrophobic moieties [25][26][27], and this is the case in our treatment (recall, that we restricted our consideration by sessile …”

Section: Contribution Into the Line Tensionmentioning

confidence: 77%

“…For the estimation of the entropic input into the line tension the threephase line is approximated by a polymer chain. This approximation is approximated by novel experimental data indicating strong orientation effects for liquid molecules located in the vicinity of hydrophobic moieties [22][23][24][25][26][27]. Thus, the polymer-chain model may be successful for sessile droplets placed on hydrophobic (say polymer) solid substrates.…”

Section: Discussionmentioning

confidence: 99%