scholarly journals Molecular Dynamics Study of the Conformation, Ion Adsorption, Diffusion and Water Structure of Soluble Polymers in Saline Solutions

Polymers ◽  
2021 ◽  
Vol 13 (20) ◽  
pp. 3550
Author(s):  
Gonzalo R. Quezada ◽  
Norman Toro ◽  
Jorge Saavedra ◽  
Pedro Robles ◽  
Iván Salazar ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Guar Gum ◽  
Molecular Level ◽  
Water Structure ◽  
Physicochemical Characteristics ◽  
Gyration Radius ◽  
Soluble Polymers ◽  
Great Consistency ◽  
Hydrolyzed Polyacrylamide ◽  
Saline Solutions

Polymers have interesting physicochemical characteristics such as charge density, functionalities, and molecular weight. Such attributes are of great importance for use in industrial purposes. Understanding how these characteristics are affected is still complex, but with the help of molecular dynamics (MD) and quantum calculations (QM), it is possible to understand the behavior of polymers at the molecular level with great consistency. This study was applied to polymers derived from polyacrylamide (PAM) due to its great use in various industries. The polymers studied include hydrolyzed polyacrylamide (HPAM), poly (2-acrylamido-2-methylpropanesulfonate) (PAMPS), polyacrylic acid (PAA), polyethylene oxide polymer (PEO), and guar gum polysaccharide (GUAR). Each one has different attributes, which help in understanding the effects on the polymer and the medium in which it is applied along a broad spectrum. The results include the conformation, diffusion, ion condensation, the structure of the water around the polymer, and interatomic polymer interactions. Such characteristics are important to selecting a polymer depending on the environment in which it is found and its purpose. The effect caused by salinity is particular to each polymer, where polymers with an explicit charge or polyelectrolytes are more susceptible to changes due to salinity, increasing their coiling and reducing their mobility in solution. This naturally reduces its ability to form polymeric bridges due to having a polymer with a smaller gyration radius. In contrast, neutral polymers are less affected in their structure, making them favorable in media with high ionic charges.

scholarly journals Physicochemical Characteristics of Arginine Enriched NaF Varnish: An In Vitro Study

Polymers ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 2998
Author(s):  
Mohammed Nadeem Bijle ◽  
Manikandan Ekambaram ◽  
Edward Lo ◽  
Cynthia Yiu
Keyword(s):  
Molecular Dynamics ◽  
Physical Properties ◽  
Artificial Saliva ◽  
Chemical Properties ◽  
In Vitro Study ◽  
Physicochemical Characteristics ◽  
Vitro Study ◽  
Physical And Chemical ◽  
Stable Matrix

The in vitro study objectives were to investigate the effect of arginine (Arg) incorporation in a 5% sodium fluoride (NaF) varnish on its physical and chemical properties including F/Arg release. Six experimental formulations were prepared with L-arginine (L-Arg) and L-arginine monohydrochloride at 2%, 4%, and 8% w/v in a 5% NaF varnish, which served as a control. The varnishes were subjected to assessments for adhesion, viscosity, and NaF extraction. Molecular dynamics were simulated to identify post-dynamics total energy for NaF=Arg/Arg>NaF/Arg<NaF concentrations. The Arg/F varnish release profiles were determined in polyacrylic lactate buffer (pH-4.5; 7 days) and artificial saliva (pH-7; 1 h, 24 h, and 12 weeks). Incorporation of L-Arg in NaF varnish significantly influences physical properties ameliorating retention (p < 0.001). L-Arg in NaF varnish institutes the Arg-F complex. Molecular dynamics suggests that NaF>Arg concentration denotes the stabilized environment compared to NaF<Arg (p < 0.001). The 2% Arg-NaF exhibits periodic perennial Arg/F release and shows significantly higher integrated mean F release than NaF (p < 0.001). Incorporating 2% L-arginine in 5% NaF varnish improves its physical properties and renders a stable matrix with enduring higher F/Arg release than control.

Molecular Dynamics Simulations to Elucidate Translocation and Permeation of Active from Lipid Nanoparticle to Skin: Complemented with Experiments

Nanoscale ◽  
2021 ◽  
Author(s):  
Krishna M. Gupta ◽  
Surajit Das ◽  
Pui Shan Chow
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Molecular Level ◽  
Skin Layer ◽  
Lipid Nanoparticle ◽  
Dynamics Simulations

One of the most realistic approaches that could deliver actives (pharmaceuticals/cosmetics) deep into skin layer is encapsulation into nanoparticles (NP). Nonetheless, molecular-level understanding into the mechanism of active delivery from...

On the interface of organic aerosols: molecular level understanding of surface melting, mixing and water adsorption/desorption dynamics

2021 ◽  
Author(s):  
Josip Lovrić ◽  
Xiangrui Kong ◽  
Sofia M. Johansson ◽  
Erik S. Thomson ◽  
Jan B. C. Pettersson
Keyword(s):  
Physical Chemistry ◽  
Molecular Dynamics ◽  
Melting Point ◽  
Molecular Beam ◽  
Molecular Level ◽  
Organic Aerosols ◽  
Md Simulations ◽  
Valeric Acid ◽  
Good Representative ◽  
Hydrophilic Character

&lt;p&gt;The detailed description of organic aerosols surfaces in the atmosphere remains an open issue, which limits our ability to understand and predict environmental change. Important research questions concern the hydrophobic/hydrophilic character of fresh and aged aerosols and the related influence on water uptake in solid, liquid as well in intermediate state. &amp;#160;Also, surface characterization remains big challenge but we find it reachable by conjunction of Molecular Dynamics (MD) simulations and the environmental molecular beam (EMB) experimental method.&amp;#160; A &amp;#160;picture of the detailed molecular-level behavior of water molecules on organic surfaces is beginning to rise based on detailed experimental and theoretical studies; one example is a recent study that investigates water interactions with solid and liquid n-butanol near the melting point [1], another example focus on interaction of water with solid nopinone [2]. From the other side, in order to characterize surface properties during and before melting we employ MD simulations of n-butanol, nopinone and valeric acid. Nopinone (C&lt;sub&gt;9&lt;/sub&gt;H&lt;sub&gt;14&lt;/sub&gt;O) is a reaction product formed during oxidation of &amp;#946;-pinene and has been found in both the gas and particle phases of atmospheric aerosol. n-butanol (C&lt;sub&gt;4&lt;/sub&gt;H&lt;sub&gt;9&lt;/sub&gt;OH) is primary alcohol, naturally occurs scarcely and here serves as good representative for alcohols. In the same way valeric acid (CH&lt;sub&gt;3&lt;/sub&gt;(CH&lt;sub&gt;2&lt;/sub&gt;)&lt;sub&gt;3&lt;/sub&gt;COOH) serves as a good representative for a family of carboxylic acids. Valeric acid is, as n-butanol, straight-chain molecule. We show that a classical force field for organic material is able to model crystal and liquid structures. The surface properties near the melting point of the condensed phase are reported, and the hydrophobic and hydrophilic character of the surface layer is discussed. &amp;#160;Overall surface melting dynamic is presented and quantified in the terms of structural and geometrical properties. Mixing of a methanol with the solid nopinone surface is examined and hereby presented.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;References&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;[1] Johansson, S. M., Lovri&amp;#263;, J., Kong, X., Thomson, E. S., Papagiannakopoulos, P., Briquez, S., Toubin, C, Pettersson, J. B. C. (2019). Understanding water interactions with organic surfaces: environmental molecular beam and molecular dynamics studies of the water&amp;#8211;butanol system. Physical Chemistry Chemical Physics. https://doi.org/10.1039/C8CP04151B&amp;#160;&amp;#160;&amp;#160;&lt;/p&gt;&lt;p&gt;[2] Johansson, S. M., Lovri&amp;#263;, J., Kong, X., Thomson, E. S., Hallquist, M., &amp; Pettersson, J. B. C. (2020). Experimental and Computational Study of Molecular Water Interactions with Condensed Nopinone Surfaces Under Atmospherically Relevant Conditions. The Journal of Physical Chemistry A, acs.jpca.9b10970. https://doi.org/10.1021/acs.jpca.9b10970&lt;/p&gt;&lt;p&gt;Keywords: Molecular Dynamics, organic crystal, organic aerosols, water uptake, surface procesess, molecular level&lt;/p&gt;

scholarly journals Three- and Four-Site Models for Heavy Water: SPC/E-HW, TIP3P-HW, and TIP4P/2005-HW

2021 ◽  
Author(s):  
Johanna-Barbara Linse ◽  
Jochen S. Hub
Keyword(s):  
Molecular Dynamics ◽  
Heavy Water ◽  
Room Temperature ◽  
Deuterium Oxide ◽  
Water Structure ◽  
Light Water ◽  
Pair Potentials ◽  
Effective Pair ◽  
Water Models ◽  
Dynamics Simulations

Heavy water or deuterium oxide, D<sub>2</sub>O, is used as solvent in various biophysical and chemical experiments. To model such experiments with molecular dynamics simulations, effective pair potentials for heavy water are required that reproduce the well-known physicochemical differences relative to light water. We present three effective pair potentials for heavy water, denoted SPC/E-HW, TIP3P-HW, and TIP4P/2005-HW. The models were parametrized by modifying widely used three- and four-site models for light water, with aim of maintaining the specific characteristics of the light water models. At room temperature, the SPC/E-HW and TIP3P-HW capture the modulations relative to light water of the mass and electron densities, heat of vaporization, diffusion coefficient, and water structure. TIP4P/2005-HW captures in addition the density of heavy water over a wide temperature range.

scholarly journals Three- and Four-Site Models for Heavy Water: SPC/E-HW, TIP3P-HW, and TIP4P/2005-HW

2021 ◽  
Author(s):  
Johanna-Barbara Linse ◽  
Jochen S. Hub
Keyword(s):  
Molecular Dynamics ◽  
Heavy Water ◽  
Room Temperature ◽  
Deuterium Oxide ◽  
Water Structure ◽  
Light Water ◽  
Pair Potentials ◽  
Effective Pair ◽  
Water Models ◽  
Dynamics Simulations

Heavy water or deuterium oxide, D<sub>2</sub>O, is used as solvent in various biophysical and chemical experiments. To model such experiments with molecular dynamics simulations, effective pair potentials for heavy water are required that reproduce the well-known physicochemical differences relative to light water. We present three effective pair potentials for heavy water, denoted SPC/E-HW, TIP3P-HW, and TIP4P/2005-HW. The models were parametrized by modifying widely used three- and four-site models for light water, with aim of maintaining the specific characteristics of the light water models. At room temperature, the SPC/E-HW and TIP3P-HW capture the modulations relative to light water of the mass and electron densities, heat of vaporization, diffusion coefficient, and water structure. TIP4P/2005-HW captures in addition the density of heavy water over a wide temperature range.

Molecular-level insight of hindered phenol AO-70/nitrile-butadiene rubber damping composites through a combination of a molecular dynamics simulation and experimental method

RSC Advances ◽  
2016 ◽  
Vol 6 (89) ◽  
pp. 85994-86005 ◽  
Author(s):  
Xiuying Zhao ◽  
Geng Zhang ◽  
Feng Lu ◽  
Liqun Zhang ◽  
Sizhu Wu
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Experimental Method ◽  
Molecular Level ◽  
Dynamics Simulation ◽  
Butadiene Rubber ◽  
Damping Properties ◽  
Nitrile Butadiene Rubber ◽  
Hindered Phenol

The damping properties of AO-70/NBR composites get a noteworthy increase with the introduction of AO-70—max tan δincreased by 66.9%.

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