scholarly journals Revealing the Frank–Evans “Iceberg” Structures within the Solvation Layer around Hydrophobic Solutes

2021 ◽  
Vol 125 (6) ◽  
pp. 1611-1617
Author(s):  
Joanna Grabowska ◽  
Anna Kuffel ◽  
Jan Zielkiewicz
Keyword(s):  
Hydrophobic Solutes

The Effect of Magnetic Field on the Hydration of Nanoscopic Hydrophobic N-Alkane Plates

2011 ◽  
Vol 228-229 ◽  
pp. 1007-1011
Author(s):  
Wei Wei Zhang ◽  
Long Qiu Li ◽  
Guang Yu Zhang ◽  
Hui Juan Dong
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Dynamics Simulation ◽  
Free Energy Barrier ◽  
Confined Water ◽  
Magnetic Exposure ◽  
Hydrophobic Solutes ◽  
The Magnetic Field ◽  
Density Of Water ◽  
Induced Adsorption

The effect of an external magnetic field on the hydration behavior of nanoscopic n-octane plates has been extensively investigated using molecular dynamics simulation in an isothermal-isobaric ensemble. The solute plates with different intermolecular spacing have also been considered to examine the effect of the topology of hydrophobic plates on the adsorption behavior of confined water in the presence of an external magnetic field with an intensity ranging from 0.1T to 1 T. The results demonstrate that magnetic exposure decreases the density of water for the plates with intermolecular spacing of a0 = 4 and 5 Å. This suggests that the free energy barrier for evaporation can be lowered by the applied field, and the hydrophobic solutes consisting of condensed n-octane molecules are apt to aggregate in the aqueous solution. In contrast, the magnetic field improves the dissolution or wetting of solutes comprised of loosely packed n-octane plates of a0=7Å. A magnetic-field-induced adsorption-to-desorption translation, which is in agreement with the experimental results provided by Ozeki, has also been observed for the plates with intermolecular spacing of a0 = 6 Å.

The entropy of hydration of simple hydrophobic solutes

1994 ◽  
Vol 51 (2-3) ◽  
pp. 349-357 ◽  
Author(s):  
Michael E. Paulaitis ◽  
Henry S. Ashbaugh ◽  
Shekhar Garde
Keyword(s):  
Hydrophobic Solutes

scholarly journals Size dependence of hydrophobic hydration at electrified gold/water interfaces

2021 ◽  
Vol 118 (15) ◽  
pp. e2023867118
Author(s):  
Alessandra Serva ◽  
Mathieu Salanne ◽  
Martina Havenith ◽  
Simone Pezzotti
Keyword(s):  
Free Energy ◽  
Energy Cost ◽  
Correction Term ◽  
Hydrophobic Hydration ◽  
Outer Sphere ◽  
Gold Surface ◽  
Electrochemical Reactions ◽  
Water Interface ◽  
Hydrophobic Solutes ◽  
Small Hydrophobic

Hydrophobic hydration at metal/water interfaces actively contributes to the energetics of electrochemical reactions, e.g. CO2 and N2 reduction, where small hydrophobic molecules are involved. In this work, constant applied potential molecular dynamics is employed to study hydrophobic hydration at a gold/water interface. We propose an adaptation of the Lum–Chandler–Weeks (LCW) theory to describe the free energy of hydrophobic hydration at the interface as a function of solute size and applied voltage. Based on this model we are able to predict the free energy cost of cavity formation at the interface directly from the free energy cost in the bulk plus an interface-dependent correction term. The interfacial water network contributes significantly to the free energy, yielding a preference for outer-sphere adsorption at the gold surface for ideal hydrophobes. We predict an accumulation of small hydrophobic solutes of sizes comparable to CO or N2, while the free energy cost to hydrate larger hydrophobes, above 2.5-Å radius, is shown to be greater at the interface than in the bulk. Interestingly, the transition from the volume dominated to the surface dominated regimes predicted by the LCW theory in the bulk is also found to take place for hydrophobes at the Au/water interface but occurs at smaller cavity radii. By applying the adapted LCW theory to a simple model addition reaction, we illustrate some implications of our findings for electrochemical reactions.

Small-to-Large Length Scale Transition of TMAO Interaction with Hydrophobic Solutes

2021 ◽  
Author(s):  
Angelina Folberth ◽  
Swaminath Bharadwaj ◽  
Nico van der Vegt
Keyword(s):  
Molecular Dynamics ◽  
Free Energy ◽  
Md Simulations ◽  
Free Energy Calculations ◽  
Length Scale ◽  
Simulation Data ◽  
Energy Calculations ◽  
Large Length ◽  
Hydrophobic Solutes ◽  
Large Length Scale

We report the effect of trimethylamine N-oxide (TMAO) on the solvation of nonpolar solutes in water studied with molecular dynamics (MD) simulations and free-energy calculations. The simulation data indicate the...

The heat capacities and volumes of some low molecular weight amides, ketones, esters, and ethers in water over the whole solubility range

1978 ◽  
Vol 56 (22) ◽  
pp. 2808-2814 ◽  
Author(s):  
Geneviève Roux ◽  
Gérald Perron ◽  
Jacques E. Desnoyers
Keyword(s):  
Hydrophobic Interactions ◽  
Heat Capacities ◽  
Initial Slope ◽  
Pure Liquid ◽  
Factors Affecting ◽  
Solubility Range ◽  
Low Concentrations ◽  
Hydrophobic Solutes ◽  
Molal Volumes ◽  
Apparent Molal Heat Capacities

The densities and heat capacities per unit volume of aqueous solutions of propionamide, methylacetate, ethylacetate, methylethylketone and diethylketone, and bis(2-ethoxyethyl)ether were measured over the whole solubility range with a flow densimeter and a flow microcalorimeter. Most systems were studied at 10, 25, and 40 °C. Properties of the pure liquids were also measured whenever possible. The derived apparent molal volumes [Formula: see text] all decrease with concentration in the water-rich region, except with ethyl acetate which increases at high temperature. In general the more hydrophobic the solute the more negative the initial slope. All apparent molal heat capacities [Formula: see text] decrease as a function of concentration and the decrease is more important for more hydrophobic solutes. The apparent molal expansibilities [Formula: see text] are obtained from [Formula: see text]. They are positive for all solutes but, at low concentrations, they are smaller than the corresponding molar value of the pure liquid. Various factors affecting hydrophobic interactions are examined.

scholarly journals Outer Membrane Permeability Barrier in Escherichia coli Mutants That Are Defective in the Late Acyltransferases of Lipid A Biosynthesis

1999 ◽  
Vol 43 (6) ◽  
pp. 1459-1462 ◽  
Author(s):  
Martti Vaara ◽  
Marjatta Nurminen
Keyword(s):  
Escherichia Coli ◽  
Membrane Permeability ◽  
Outer Membrane ◽  
Lipid A ◽  
Enteric Bacteria ◽  
Normal Function ◽  
Permeability Barrier ◽  
Core Oligosaccharide ◽  
Hydrophobic Solutes ◽  
Outer Membrane Permeability

ABSTRACT The tight packing of six fatty acids in the lipid A constituent of lipopolysaccharide (LPS) has been proposed to contribute to the unusually low permeability of the outer membrane of gram-negative enteric bacteria to hydrophobic antibiotics. Here it is shown that theEscherichia coli msbB mutant, which elaborates defective, penta-acylated lipid A, is practically as resistant to a representative set of hydrophobic solutes (rifampin, fusidic acid, erythromycin, clindamycin, and azithromycin) as the parent-type control strain. The susceptibility index, i.e., the approximate ratio between the MIC for the msbB mutant and that for the parent-type control, was maximally 2.7-fold. In comparison, the rfa mutant defective in the deep core oligosaccharide part of LPS displayed indices ranging from 20 to 64. The lpxA and lpxD lipid A mutants had indices higher than 512. Furthermore, the msbBmutant was resistant to glycopeptides (vancomycin, teicoplanin), whereas the rfa, lpxA, and lpxDmutants were susceptible. The msbB htrB double mutant, which elaborates even-more-defective, partially tetra-acylated lipid A, was still less susceptible than the rfa mutant. These findings indicate that hexa-acylated lipid A is not a prerequisite for the normal function of the outer membrane permeability barrier.

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