@article {178, title = {Polarized Water Wires under Confinement in Chiral Channels}, journal = {The Journal of Physical Chemistry B}, volume = {119}, year = {2015}, month = {Jul-16-2015}, pages = {8707 - 8717}, abstract = {
Abstract Image

The alignment of water molecules along chiral pores may activate proton/ion conduction along dipolar hydrophilic pathways. Here we show that a simple synthetic \“T-channel\” forms a directional pore with its carbonyl moieties solvated by chiral helical water wires. Atom-scale simulations and experimental crystallographic assays reveal a dynamical structure of water and electrolyte solutions (alkali metal chlorides) confined in these organic T-channels. Oscillations in the dipole orientation, which correspond to alternative ordering (dipole up\–dipole down) of the water molecules with a period of about 4.2 \Å (imposed by the distance between two successive carbonyl groups) are observed. When ions are added to the system, despite the strong Coulombic water/ion interaction, confined water remains significantly ordered in the T-channel and still exhibits surface-induced polarization. Cation permeation can be achieved through alternated hydration\–dehydration occurring along strongly oriented water wires. The T-channel, which exhibits chirality with strong water orientation, provides an opportunity to unravel novel water-channel systems that share many interesting properties of biomolecular systems.

}, issn = {1520-6106}, doi = {10.1021/acs.jpcb.5b03322}, author = {Barboiu, Mihail and Pierre-Andre Cazade and Le Duc, Yann and Yves-Marie Legrand and Arie Van Der Lee and Benoit A. Coasne} } @article {107, title = {An artificial primitive mimic of the Gramicidin-A channel}, journal = {Nature Communications}, volume = {5}, year = {2014}, month = {Jun-26-2014}, type = {Article}, abstract = {

Gramicidin A (gA) is the simplest known natural channel, and important progress in improving conduction activity has previously been obtained with modified natural gAs. However, simple artificial systems mimicking the gA functions are unknown. Here we show that gA can be mimicked using a simple synthetic triazole or {\textquoteleft}T-channel\&$\#$39; forming compound (TCT), having similar constitutional functions as the natural gAs. As in gA channels, the carbonyl moieties of the TCT, which point toward the T-channel core and surround the transport direction, are solvated by water. The net-dipolar alignment of water molecules along the chiral pore surfaces influences the conduction of protons/ions, envisioned to diffuse along dipolar hydrophilic pathways. Theoretical simulations and experimental assays reveal that the conduction through the T-channel, similar to that in gA, presents proton/water conduction, cation/anion selectivity and large open channel-conductance states. T-channels-associating supramolecular chirality with dipolar water alignment-represent an artificial primitive mimic of gA.

Molecular structures and crystal packing.

Molecular simulations of water molecules and ions confined within T-channel.

Bilayer membrane transport experiments.

Single channel conductance of T-channels under {\textquoteleft}early stage{\textquoteright} conductance records.

}, issn = {2041-1723}, doi = {10.1038/ncomms5142}, author = {Barboiu, Mihail and Le Duc, Yann and Gilles, Arnaud and Pierre-Andre Cazade and Michau, Mathieu and Yves-Marie Legrand and Arie Van Der Lee and Benoit A. Coasne and Parvizi, Paria and Post, Joshua and Fyles, Thomas} } @article {63, title = {Structure and Dynamics of an Electrolyte Confined in Charged Nanopores}, journal = {The Journal of Physical Chemistry C}, volume = {118}, year = {2014}, month = {Feb-2014}, pages = {5061{\textendash}5072}, abstract = {
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Molecular Dynamics simulations are used to investigate the structure and dynamics of an aqueous electrolyte (NaCl) confined within a nanomembrane, which consists of a nanopore with a diameter 3 nm having a negatively charged surface. Both nanomembranes with a diffuse charge and with local charges are considered (in both cases, two surface charge densities are considered, \−0.9 e/nm2 and \−1.8 e/nm2). For all nanomembranes, significant layering of water and ions in the vicinity of the nanomembrane surface is observed. While the distribution of water and chloride ions is nearly insensitive to the nanomembrane charge and type, the arrangement of sodium cations within the nanomembrane depends on the system being considered. The water and ion density profiles in the nanomembranes are compared with the predictions of a modified Poisson\–Boltzmann equation in which charge image, solvation effects, and dispersion interactions with the surface are taken into account [Huang et al. Langmuir, 2008, 24, 1442]. The self-diffusion coefficient for a given species is smaller than its bulk counterpart and is at most 75\% of the bulk value. While the self-diffusion coefficients for water and sodium cations decrease with decreasing the overall negative charge of the nanomembrane, the self-diffusion coefficient for the chloride anions is nearly independent of the nanomembrane type and charge. We also estimate the dynamics of the confined aqueous electrolyte by calculating time correlation functions which allow estimating solvation, ion pairing, and residence times.

}, isbn = {1932-7447}, doi = {10.1021/jp4098638}, author = {Pierre-Andre Cazade and Hartkamp, Remco and Benoit A. Coasne} } @article {76, title = {Molecular intermittent dynamics of interfacial water: probing adsorption and bulk confinement}, journal = {Soft Matter}, volume = {9}, year = {2013}, month = {Jul-26-2013}, pages = {8654-8663}, type = {Article}}, abstract = {

Numerous natural and manufactured systems such as colloidal suspensions, geological pore networks, catalysts, and nanofluidic devices develop a large and sometimes complex interface strongly influencing the dynamics of the fluid entrapped inside these materials. A coarse grain picture of this molecular dynamics can be considered as an intermittence of adsorption steps and bulk relocations from one point to another point of the interface. Adsorption statistics such as the adsorption time distribution and its first moment reflect the degree of interaction of the molecule with the colloidal interface. Relocation statistics strongly depend on the shape of the pore, the surface forces and the bulk confinement. In this paper, a theoretical analysis of this intermittent dynamics is presented. A direct comparison with molecular dynamics simulations is proposed in the case of liquid water confined inside a hydrophilic substrate (silica slit pore with hydroxylated surfaces) or inside a hydrophobic substrate (carbon nanotube). Analysis of this intermittent dynamics allows quantification of the level of interaction of the vicinal water with the solid interface inside an independent adsorption region in exchange with the confined bulk fluid. The possibility of experimentally probing this dynamics using NMR relaxometry is emphasized.

}, issn = {1744-683X}, doi = {10.1039/c3sm51940f}, author = {Pierre E. Levitz and Patrick A Bonnaud and Pierre-Andre Cazade and Roland Jean-Marc Pellenq and Benoit A. Coasne} }