scholarly journals Density of Phonon States in Cubic Ice Ic

Author(s):  
Leonardo del Rosso ◽  
Milva Celli ◽  
Daniele Colognesi ◽  
Svemir Rudic ◽  
Niall J. English ◽  
...  

The measurement of the H-projected density of phonon states (H-DOPS) of polycrystalline ice Ic has been performed with an unprecedented accuracy, and in a sample having an almost perfect crystallographic purity, as it was obtained from the transformation of ice XVII. Results are compared with new accurate measurements of H-DOPS in ice Ih, and with centroid molecular-dynamics (MD) computations. The differences between the experimental H-DOPS in these two forms of ice are subtle, but quantitatively measurable. In addition, they are reproduced semi-quantitatively by computational methods, demonstrating the effectiveness of this innovative simulation tool for reproducing the dynamical properties of the ice structures.

2021 ◽  
Author(s):  
Leonardo del Rosso ◽  
Milva Celli ◽  
Daniele Colognesi ◽  
Svemir Rudic ◽  
Niall J. English ◽  
...  

The measurement of the H-projected density of phonon states (H-DOPS) of polycrystalline ice Ic has been performed with an unprecedented accuracy, and in a sample having an almost perfect crystallographic purity, as it was obtained from the transformation of ice XVII. Results are compared with new accurate measurements of H-DOPS in ice Ih, and with centroid molecular-dynamics (MD) computations. The differences between the experimental H-DOPS in these two forms of ice are subtle, but quantitatively measurable. In addition, they are reproduced semi-quantitatively by computational methods, demonstrating the effectiveness of this innovative simulation tool for reproducing the dynamical properties of the ice structures.


2021 ◽  
Vol 22 (13) ◽  
pp. 7139
Author(s):  
Wojciech Bocian ◽  
Elżbieta Bednarek ◽  
Katarzyna Michalska

Molecular modeling (MM) results for tedizolid and radezolid with heptakis-(2,3-diacetyl-6-sulfo)-β-cyclodextrin (HDAS-β-CD) are presented and compared with the results previously obtained for linezolid and sutezolid. The mechanism of interaction of chiral oxazolidinone ligands belonging to a new class of antibacterial agents, such as linezolid, tedizolid, radezolid, and sutezolid, with HDAS-β-CD based on capillary electrokinetic chromatography (cEKC), nuclear magnetic resonance (NMR) spectroscopy, and MM methods was described. Principles of chiral separation of oxazolidinone analogues using charged single isomer derivatives of cyclodextrin by the cEKC method were presented, including the selection of the optimal chiral selector and separation conditions, complex stoichiometry, and binding constants, which provided a comprehensive basis for MM studies. In turn, NMR provided, where possible, direct information on the geometry of the inclusion complexes and also provided the necessary structural information to validate the MM calculations. Consequently, MM contributed to the understanding of the structure of diastereomeric complexes, the thermodynamics of complexation, and the visualization of their structures. The most probable mean geometries of the studied supramolecular complexes and their dynamics (geometry changes over time) were determined by molecular dynamics methods. Oxazolidinone ligands have been shown to complex mainly the inner part of cyclodextrin, while the external binding is less privileged, which is consistent with the conclusions of the NMR studies. Enthalpy values of binding of complexes were calculated using long-term molecular dynamics in explicit water as well as using molecular mechanics, the Poisson–Boltzmann or generalized Born, and surface area continuum solvation (MM/PBSA and MM/GBSA) methods. Computational methods predicted the effect of changes in pH and composition of the solution on the strength and complexation process, and it adapted the conditions selected as optimal during the cEKC study. By changing the dielectric constant in the MM/PBSA and MM/GBSA calculations, the effect of changing the solution to methanol/acetonitrile was investigated. A fairly successful attempt was made to predict the chiral separation of the oxazolidinones using the modified cyclodextrin by computational methods.


Author(s):  
Shi-Wei Ren

In this paper, the geometric structures and the melting-like processes of the 13-atom pure copper, pure cobalt cluster and their 13-atom mixed clusters are investigated and compared by the molecular dynamics method. The calculation shows that the pure copper and cobalt clusters have the standard icosahedral structures and the mixed clusters take on the deformed icosahedral structures. The quantitative analysis shows that the deformations are slight. Moreover, an element similarity function is introduced by which the contribution of the compositions of the clusters to the deformation of the mixed clusters is analyzed and discussed. With the increase of the temperature, the migrating and recombination of the atoms on the surface of the clusters are observed, indicating the starting of the transition from solid-like to liquid-like state for the clusters. Through the calculating of the relative root-mean-squared pair separation fluctuation and monitoring the dynamical structures of the clusters, it is found that the mixed clusters experience a multi-step process in the transition.


2020 ◽  
Vol 55 (S3) ◽  
pp. 14-45

Although ion channels are crucial in many physiological processes and constitute an important class of drug targets, much is still unclear about their function and possible malfunctions that lead to diseases. In recent years, computational methods have evolved into important and invaluable approaches for studying ion channels and their functions. This is mainly due to their demanding mechanism of action where a static picture of an ion channel structure is often insufficient to fully understand the underlying mechanism. Therefore, the use of computational methods is as important as chemical-biological based experimental methods for a better understanding of ion channels. This review provides an overview on a variety of computational methods and software specific to the field of ion-channels. Artificial intelligence (or more precisely machine learning) approaches are applied for the sequence-based prediction of ion channel family, or topology of the transmembrane region. In case sufficient data on ion channel modulators is available, these methods can also be applied for quantitative structureactivity relationship (QSAR) analysis. Molecular dynamics (MD) simulations combined with computational molecular design methods such as docking can be used for analysing the function of ion channels including ion conductance, different conformational states, binding sites and ligand interactions, and the influence of mutations on their function. In the absence of a three-dimensional protein structure, homology modelling can be applied to create a model of your ion channel structure of interest. Besides highlighting a wide range of successful applications, we will also provide a basic introduction to the most important computational methods and discuss best practices to get a rough idea of possible applications and risks.


2015 ◽  
Vol 15 (2) ◽  
pp. 155-162 ◽  
Author(s):  
Suwardi Suwardi ◽  
Harno Dwi Pranowo ◽  
Ria Armunanto

A QM/MM molecular dynamics (MD) simulation has been carried out using three-body corrected pair potential to investigate the structural and dynamical properties of Zr4+ in dilute aqueous solution. Structural data in the form of radial distribution function, coordination number distribution, and angular distribution function were obtained. The results indicate eight water molecules coordinate to zirconium ion and have two angles of O-Zr4+-O, i.e. 72.0° and 140.0° with a Zr4+-O distance of 2.34 Å. According to these results, the hydration structure of Zr4+ ion in water was more or less well-defined square antiprismatic geometry. The dynamical properties have been characterized by the ligand’s mean residence time (MRT) and Zr4+-O stretching frequencies. The inclusion of the three-body correction was important for the description of the hydrated Zr4+ ion, and the results indicated in good agreement with experimental values.


2017 ◽  
Vol 53 (27) ◽  
pp. 3830-3833 ◽  
Author(s):  
Andreia de Almeida ◽  
Andreia F. Mósca ◽  
Darren Wragg ◽  
Margot Wenzel ◽  
Paul Kavanagh ◽  
...  

The mechanism of inhibition of water and glycerol permeation via human aquaglyceroporin-3 (AQP3) by gold(iii) complexes has been described, for the first time, using molecular dynamics (MD), combined with density functional theory (DFT) and electrochemical studies.


2018 ◽  
Vol 20 (1) ◽  
pp. 435-448 ◽  
Author(s):  
Majid Moosavi ◽  
Fatemeh Khashei ◽  
Elaheh Sedghamiz

The structural and dynamical properties of two dicationic ionic liquids, i.e. [Cn(mim)2][NTf2]2 with n = 3 and 5, have been studied to obtain a fundamental understanding of the molecular basis of the macroscopic and microscopic properties of the bulk liquid phase.


2020 ◽  
Vol 22 (3) ◽  
pp. 1154-1167 ◽  
Author(s):  
Khair Bux ◽  
Syed Tarique Moin

Molecular dynamics simulations were applied to an isolated cholesterol immersed in four different solvents of varying polarity, such as water, methanol, dimethyl sulfoxide and benzene, to gain insights into the structural and dynamical properties.


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