Origin of ion selectivity at the air/water interface

2015 ◽  
Vol 17 (6) ◽  
pp. 4311-4318 ◽  
Author(s):  
Lu Sun ◽  
Xin Li ◽  
Yaoquan Tu ◽  
Hans Ågren
Keyword(s):  
Hydrogen Bonds ◽  
Weak Interactions ◽  
Ion Selectivity ◽  
Hydration Shell ◽  
Water Molecules ◽  
Water Interface ◽  
Hydration Shells ◽  
Air Water Interface ◽  
Water Hydrogen ◽  
First Hydration Shell

A snapshot of a water droplet consisting of Cs+ and I− ions with their hydration structures displayed. I− is hydrated anisotropically and the water–water hydrogen bonds in the first hydration shell are hindered. The anions have quite weak interactions with non-hydrogen-bonded water molecules in the first hydration shell, making it easier for them to leave the site. In contrast, cations obtain more stable hydration shells with an increase in their size.

Temperature Dependence of the Air/Water Interface Revealed by Polarization Sensitive Sum-Frequency Generation Spectroscopy

2018 ◽  
Author(s):  
Daniel R. Moberg ◽  
Shelby C. Straight ◽  
Francesco Paesani
Keyword(s):  
Temperature Dependence ◽  
Low Frequency ◽  
Potential Energy Function ◽  
Md Simulations ◽  
Sum Frequency Generation ◽  
Water Molecules ◽  
Water Interface ◽  
Sum Frequency ◽  
Air Water Interface ◽  
Frequency Generation

<div> <div> <div> <p>The temperature dependence of the vibrational sum-frequency generation (vSFG) spectra of the the air/water interface is investigated using many-body molecular dynamics (MB-MD) simulations performed with the MB-pol potential energy function. The total vSFG spectra calculated for different polarization combinations are then analyzed in terms of molecular auto-correlation and cross-correlation contributions. To provide molecular-level insights into interfacial hydrogen-bonding topologies, which give rise to specific spectroscopic features, the vSFG spectra are further investigated by separating contributions associated with water molecules donating 0, 1, or 2 hydrogen bonds to neighboring water molecules. This analysis suggests that the low frequency shoulder of the free OH peak which appears at ∼3600 cm−1 is primarily due to intermolecular couplings between both singly and doubly hydrogen-bonded molecules. </p> </div> </div> </div>

scholarly journals Hyaluronan orders water molecules in its nanoscale extended hydration shells

2021 ◽  
Vol 7 (10) ◽  
pp. eabf2558
Author(s):  
J. Dedic ◽  
H. I. Okur ◽  
S. Roke
Keyword(s):  
Second Harmonic ◽  
Hydration Shell ◽  
Water Molecules ◽  
Temperature Dependent ◽  
Flexible Chain ◽  
Optical Modeling ◽  
Hydration Shells ◽  
Second Harmonic Scattering ◽  
Nuclear Quantum Effects ◽  
Extracellular Environment

Hyaluronan (HA) is an anionic, highly hydrated bio-polyelectrolyte found in the extracellular environment, like the synovial fluid between joints. We explore the extended hydration shell structure of HA in water using femtosecond elastic second-harmonic scattering (fs-ESHS). HA enhances orientational water-water correlations. Angle-resolved fs-ESHS measurements and nonlinear optical modeling show that HA behaves like a flexible chain surrounded by extended shells of orientationally correlated water. We describe several ways to determine the concentration-dependent size and shape of a polyelectrolyte in water, using the amount of water oriented by the polyelectrolyte charges as a contrast agent. The spatial extent of the hydration shell is determined via temperature-dependent measurements and can reach up to 475 nm, corresponding to a length of 1600 water molecules. A strong isotope effect, stemming from nuclear quantum effects, is observed when light water (H2O) is replaced by heavy water (D2O), amounting to a factor of 4.3 in the scattered SH intensity.

The interaction of protein monolayers with dissolved proteins - I. Fibrinogen, thrombin and plasma albumin

1956 ◽  
Vol 145 (921) ◽  
pp. 554-563 ◽  
Keyword(s):  
Hydrogen Bonds ◽  
Specific Interaction ◽  
Viscosity Data ◽  
Water Interface ◽  
Plasma Albumin ◽  
Intermediate Area ◽  
Ionic Groups ◽  
Maximum Value ◽  
Rate Of Increase ◽  
Air Water Interface

The proteins concerned have been spread at the air/water interface on a substrate at physio­logical ionic strengths. Spread protein A has been ‘injected’ with dissolved protein B , and the increase in pressure observed has been attributed to adsorption. This adsorption has been found to depend on the area per molecule of the spread protein, reaching a maximum value at an intermediate area value. It is postulated that adsorption occurs by hydrogen bonds between B and A , and that at a certain stage of compression the bonding groups in A turn so as to form hydrogen bonds within the monolayer, a theory which accords with compressibility and viscosity data on the monolayers. The rate of increase of pressure depends markedly on ionic strength suggesting that the rate of adsorption is influenced by the interaction of ionic groups in A and B . No evidence was obtained for a surface clotting reaction or specific interaction between fibrinogen and thrombin, whichever protein formed the monolayer, suggesting that the specific interaction involves at least two groups in each protein held at a critical spacing.

[N,N′-Bis(diphenylphosphino)pyridine-2,6-diamine-κ3 P,N 1,P′]chloropalladium(II) chloride monohydrate 1,2-dichloroethane solvate

2006 ◽  
Vol 62 (5) ◽  
pp. m1106-m1108 ◽  
Author(s):  
Julia Wiedermann ◽  
David Benito-Garagorri ◽  
Karl Kirchner ◽  
Kurt Mereiter
Keyword(s):  
Hydrogen Bonds ◽  
Title Compound ◽  
Weak Interactions ◽  
Water Molecules ◽  
Square Planar ◽  
Chloride Monohydrate

The title compound, [PdCl(C29H25N3P2)]Cl·H2O·C2H4Cl2, contains a cationic pincer-type PNP complex with Pd in a square-planar coordination. The complexes form dimers which are π–π stacked via their pyridine rings and linked into chains via hydrogen bonds via four-membered rings of two chloride anions and two water molecules. Pairs of 1,2-dichloroethane molecules are entrapped in pockets of the structure and show weak interactions with palladium.

The Second Hydration Shell of Li+ in Aqueous LiI from X-Ray and MD Studies

1981 ◽  
Vol 36 (10) ◽  
pp. 1076-1082 ◽  
Author(s):  
T. Radnai ◽  
G. Pálinkás ◽  
Gy I. Szász ◽  
K. Heinzinger
Keyword(s):  
Hydration Shell ◽  
Distribution Functions ◽  
Dynamics Simulation ◽  
Scattering Data ◽  
Water Molecules ◽  
Radial Distribution Functions ◽  
Partial Structure ◽  
X Ray ◽  
Total Structure ◽  
First Hydration Shell

Indications from a molecular dynamics simulation of a 2.2 molal LiI solution of the existence of a second hydration shell of Li+ have been checked by an x-ray investigation of the same solution. The scattering data are analysed via partial structure functions and radial distribution functions which have been obtained from a model fitted to the total structure function. Experiment and simulation agree on first neighbor ion-water distances. An octahedral arrangement of six water molecules in the first hydration shell of Li+ and additional twelve water molecules in the second shell have been verified by the experiment.

scholarly journals Orientation and Motion of Water Molecules at Air/Water Interface

2006 ◽  
Vol 19 (1) ◽  
pp. 20-24 ◽  
Author(s):  
Wei Gan ◽  
Dan Wu ◽  
Zhen Zhang ◽  
Yuan Guo ◽  
Hong-fei Wang
Keyword(s):  
Water Molecules ◽  
Water Interface ◽  
Air Water Interface

A Molecular Dynamics Study of the Structure of an Aqueous CsF Solution

1983 ◽  
Vol 38 (2) ◽  
pp. 214-224 ◽  
Author(s):  
Gy. I. Szász ◽  
K. Heinzinger
Keyword(s):  
Molecular Dynamics ◽  
Hydration Shell ◽  
Distribution Functions ◽  
Dynamics Simulation ◽  
Water Model ◽  
Water Molecules ◽  
Heat Of Solution ◽  
Average Temperature ◽  
Experimental Density ◽  
First Hydration Shell

Abstract A molecular dynamics simulation of a 2.2 molal aqueous CsF solution has been performed employing the ST2 water model. The basic periodic cube with a sidelength of 18.50 Å contained 200 water molecules, and 8 ions of each kind, corresponding to an experimental density of 1.26 g/cm3. The simulation extended over 6.5 ps with an average temperature of 307 K. The structure of the solution is discussed by means of radial distribution functions and the orientation of the water molecules. The computed hydration numbers in the first shell of Cs+ and F- are 7.9 and 6.8, respectively; the corresponding first hydration shell radii are 3.22 A and 2.64 A, respectively. Values for the hydration shell energies and the heat of solution have been calculated.

Polarization-Modulated FT-IR Spectroscopy of a Spread Monolayer at the Air/Water Interface

1993 ◽  
Vol 47 (7) ◽  
pp. 869-874 ◽  
Author(s):  
D. Blaudez ◽  
T. Buffeteau ◽  
J. C. Cornut ◽  
B. Desbat ◽  
N. Escafre ◽  
...  
Keyword(s):  
Ir Spectroscopy ◽  
Liquid Water ◽  
Arachidic Acid ◽  
Water Molecules ◽  
Water Interface ◽  
Vibrational Modes ◽  
Experimental Conditions ◽  
Air Water Interface ◽  
Ft Ir ◽  
Ft Ir Spectroscopy

This study devoted to the FT-IR spectroscopy of monolayers spread at the air/water interface is, to our knowledge, the first report presenting complete mid-infrared monolayer spectra perfectly extracted from the strong water vapor bands. This has been possible with the use of the polarization-modulated IRRAS method, which is not sensitive to the isotropic absorptions of the sample environment. On the basis of theoretical modeling and experiments, the best angle of incidence has been found near 76° for detection of intraplane as well as out-of-plane oriented monolayer absorptions. With the use of such experimental conditions, on the normalized difference (covered vs. uncovered water) PM-IRRAS spectra, monolayer vibrational bands come out upward or downward, depending on the orientation of their transition moment with respect to the interface. Application to the study of deuterated arachidic acid and arachidate monolayers allows observation of the vibrational modes of the polar head groups interacting with the liquid water molecules and provides some evidence of their symmetrical anchoring. The vibrational modes of the liquid water subphase contribute to these difference spectra as broad dips that certainly contain information on a possible restructuring of the water molecules at the interface.

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