Proton Conduction via Water Bridges Hydrated in the Collagen Film

Collagen films with proton conduction are a candidate of next generation of fuel-cell electrolyte. To clarify a relation between proton conductivity and formation of water networks in the collagen film originating from a tilapia’s scale, we systematically measured the ac conductivity, infrared absorption spectrum, and weight change as a function of relative humidity (RH) at room temperature. The integrated absorbance concerning an O–H stretching mode of water molecules increases above 60% RH in accordance with the weight change. The dc conductivity varies in the vicinity of 60 and 83% RH. From those results, we have determined the dc conductivity vs. hydration number (N) per unit (Gly-X-Y). The proton conduction is negligible in the collagen molecule itself, but dominated by the hydration shell, the development of which is characterized with three regions. For 0 < N < 2, the conductivity is extremely small, because the water molecule in the primary hydration shell has a little hydrogen bonded with each other. For 2 < N < 4, a quasi-one-dimensional proton conduction occurs through intra-water bridges in the helix. For 4 < N, the water molecule fills the helix, and inter-water bridges are formed in between the adjacent helices, so that a proton-conducting network is extended three dimensional.

Download Full-text

CuCl Complexation in the Vapor Phase: Insights from Ab Initio Molecular Dynamics Simulations

Geofluids ◽

10.1155/2018/4279124 ◽

2018 ◽

Vol 2018 ◽

pp. 1-12 ◽

Cited By ~ 5

Author(s):

Yuan Mei ◽

Weihua Liu ◽

A. A. Migdiov ◽

Joël Brugger ◽

A. E. Williams-Jones

Keyword(s):

Molecular Dynamics ◽

Water Molecule ◽

Ab Initio ◽

Hydration Number ◽

Hydration Shell ◽

Md Simulations ◽

Ab Initio Molecular Dynamics ◽

Low Density ◽

Fluid Density ◽

Hydration Numbers

We investigated the hydration of the CuCl0 complex in HCl-bearing water vapor at 350°C and a vapor-like fluid density between 0.02 and 0.09 g/cm3 using ab initio molecular dynamics (MD) simulations. The simulations reveal that one water molecule is strongly bonded to Cu(I) (first coordination shell), forming a linear [H2O-Cu-Cl]0 moiety. The second hydration shell is highly dynamic in nature, and individual configurations have short life-spans in such low-density vapors, resulting in large fluctuations in instantaneous hydration numbers over a timescale of picoseconds. The average hydration number in the second shell (m) increased from ~0.5 to ~3.5 and the calculated number of hydrogen bonds per water molecule increased from 0.09 to 0.25 when fluid density (which is correlated to water activity) increased from 0.02 to 0.09 g/cm3 (fH2O 1.72 to 2.05). These changes of hydration number are qualitatively consistent with previous solubility studies under similar conditions, although the absolute hydration numbers from MD were much lower than the values inferred by correlating experimental Cu fugacity with water fugacity. This could be due to the uncertainties in the MD simulations and uncertainty in the estimation of the fugacity coefficients for these highly nonideal “vapors” in the experiments. Our study provides the first theoretical confirmation that beyond-first-shell hydrated metal complexes play an important role in metal transport in low-density hydrothermal fluids, even if it is highly disordered and dynamic in nature.

Download Full-text

Prediction of Interaction of Citric Acid Modified Cellulose with Water Region Using Molecular Modelling Technique

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.797.118 ◽

2019 ◽

Vol 797 ◽

pp. 118-126

Author(s):

Nornizar Anuar ◽

Wan Nor Asyikin Wan Mohamed Daid ◽

Sopiah Ambong Khalid ◽

Sarifah Fauziah Syed Draman ◽

Siti Rozaimah Sheikh Abdullah

Keyword(s):

Hydrogen Bond ◽

Citric Acid ◽

Water Molecule ◽

Hydration Shell ◽

Computational Technique ◽

Water Molecules ◽

Ferric Ion ◽

Water Loading ◽

Higher Temperature ◽

Modified Cellulose

In this paper, chemically modified cellulose was used instead of cellulose as it offers higher adsorption capacities, great chemical strength and good resistance to heat. As part of Phyto-Adsorption Remediation Method, citric acid modified cellulose (CAMC) was used to treat ferric ion. However, there is a large possibility that CAMC molecule might interact with water molecule that contain hydrogen bond and hence pose as a competitor to ferric acid and reduces the efficiency of CAMC in ferric ion removal. Thus, the aim of this work is to identify the most stable hydrogen bond between CAMC and water, by using a computational technique. The interaction between the water molecules and CAMC was observed by varying the volume of water molecule with modified cellulose by an expansion in amorphous region. The simulation result shows that for water loading less than 20 molecules, the interaction between water molecules and CAMC is higher at temperature 311K, whilst for water loading higher than 20 molecules, the interaction weakens at higher temperature. This work proves that water molecules have the tendency to bind to carboxyl group of glucose, to oxygen of ester and to oxygen of anhydride acid of the CAMC molecule, which might pose a competition for ferric acid removal. The calculation of coordination number has shown that the number of atoms present in the first hydration shell (of radius < 2.5Å) is more as the temperature increases from 298K to 311K, which indicates that the adsorption is better at higher temperature. For hydration shell at radius >2.5Å, cell temperature is not significant to the number of atoms present.

Download Full-text

Structural Origin of the Antimagic Number in Protonated Water Clusters H+(H2O)n: Spectroscopic Observation of the “Missing” Water Molecule in the Outermost Hydration Shell

The Journal of Physical Chemistry Letters ◽

10.1021/jz200996q ◽

2011 ◽

Vol 2 (17) ◽

pp. 2130-2134 ◽

Cited By ~ 22

Author(s):

Kenta Mizuse ◽

Asuka Fujii

Keyword(s):

Water Molecule ◽

Water Clusters ◽

Hydration Shell ◽

Spectroscopic Observation

Download Full-text

Induced Polarization in MD Simulations of the 5HT3 Receptor Channel

10.1101/2020.03.01.971853 ◽

2020 ◽

Author(s):

Gianni Klesse ◽

Shanlin Rao ◽

Stephen J. Tucker ◽

Mark S.P. Sansom

Keyword(s):

Lipid Bilayers ◽

Force Fields ◽

Hydration Number ◽

Hydration Shell ◽

Chemical Properties ◽

Induced Polarization ◽

Water Model ◽

Complex Behavior ◽

Complete Wetting ◽

Polarizable Force Fields

AbstractIon channel proteins form water-filled nanoscale pores within lipid bilayers and their properties are dependent on the complex behavior of water in a nano-confined environment. Using the pore of the 5HT3 receptor (5HT3R) we compare additive with polarizable models in describing the behavior of water in nanopores. Molecular Dynamics simulations were performed with four conformations of the channel: two closed state structures, an intermediate state, and an open state, each embedded in a phosphatidylcholine bilayer. Water density profiles revealed that for all water models, the closed and intermediate states exhibited strong dewetting within the central hydrophobic gate region of the pore. However, the open state conformation exhibited varying degrees of hydration, ranging from partial wetting for the TIP4P/2005 water model, to complete wetting for the polarizable AMOEBA14 model. Water dipole moments calculated using polarizable force fields also revealed that water molecules remaining within dewetted sections of the pore resemble gas phase water. Free energy profiles for Na+ and for Cl− ions within the open state pore revealed more rugged energy landscapes using polarizable force fields, and the hydration number profiles of these ions were also sensitive to induced polarization resulting in a substantive reduction of the number of waters within the first hydration shell of Cl− whilst it permeates the pore. These results demonstrate that induced polarization can influence the complex behavior of water and ions within nanoscale pores and provides important new insights into their chemical properties.ToC Graphic

Download Full-text

Influence of effective polarization on ion and water interactions within a biomimetic nanopore

10.1101/2021.12.10.471283 ◽

2021 ◽

Author(s):

Linda X Phan ◽

Charlotte I Lynch ◽

Jason Crain ◽

Mark Sansom ◽

Stephen J Tucker

Keyword(s):

Ion Channels ◽

Hydration Number ◽

Hydration Shell ◽

Md Simulations ◽

Hydrophobic Region ◽

Density Distributions ◽

Energy Profiles ◽

Hydrophobic Pore ◽

Effective Polarization ◽

Ion Effects

Interactions between ions and water at hydrophobic interfaces within ion channels and nanopores are suggested to play a key role in the movement of ions across biological membranes. Previous molecular dynamics (MD) simulations have shown that the affinity of polarizable anions to aqueous/hydrophobic interfaces can be markedly influenced by including polarization effects through an electronic continuum correction (ECC). Here, we designed a model biomimetic nanopore to imitate the polar pore openings and hydrophobic gating regions found in pentameric ligand-gated ion channels. MD simulations were then performed using both a non-polarizable force field and the ECC method to investigate the behavior of water, Na+ and Cl- ions confined within the hydrophobic region of the nanopore. Number density distributions revealed preferential Cl- adsorption to the hydrophobic pore walls, with this interfacial layer largely devoid of Na+. Free energy profiles for Na+ and Cl- permeating the pore also display an energy barrier reduction associated with the localization of Cl- to this hydrophobic interface, and the hydration number profiles reflect a corresponding reduction in the first hydration shell of Cl-. Crucially, these ion effects were only observed through inclusion of effective polarization which therefore suggests that polarizability may be essential for an accurate description for the behavior of ions and water within hydrophobic nanoscale pores, especially those that conduct Cl-.

Download Full-text