scholarly journals Variable-Temperature 17O NMR Studies Allow Quantitative Evaluation of Molecular Dynamics in Organic Solids

2012 ◽  
Vol 134 (35) ◽  
pp. 14609-14617 ◽  
Author(s):  
Xianqi Kong ◽  
Luke A. O’Dell ◽  
Victor Terskikh ◽  
Eric Ye ◽  
Ruiyao Wang ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Quantitative Evaluation ◽  
Variable Temperature ◽  
Nmr Studies ◽  
17O Nmr ◽  
Organic Solids

scholarly journals Explanation of the Formation of Complexes between Representatives of Oxazolidinones and HDAS-β-CD Using Molecular Modeling as a Complementary Technique to cEKC and NMR

2021 ◽  
Vol 22 (13) ◽  
pp. 7139
Author(s):  
Wojciech Bocian ◽  
Elżbieta Bednarek ◽  
Katarzyna Michalska
Keyword(s):  
Molecular Dynamics ◽  
Molecular Modeling ◽  
Computational Methods ◽  
Chiral Separation ◽  
Structural Information ◽  
Binding Constants ◽  
Nmr Studies ◽  
Thermodynamics Of Complexation ◽  
Poisson Boltzmann ◽  
Explicit Water

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.

Study on the effect of temperature and strain rate on Ni2FeCrCuAl high entropy alloy: a molecular dynamics study

2021 ◽  
Vol 3 (4) ◽  
pp. 045042
Author(s):  
S Gowthaman ◽  
T Jagadeesha
Keyword(s):  
Molecular Dynamics ◽  
Strain Rate ◽  
Point Defects ◽  
Tensile Deformation ◽  
Variable Temperature ◽  
Effect Of Temperature ◽  
High Entropy Alloy ◽  
High Entropy ◽  
Beneficial Impact ◽  
The Impact

Abstract High entropy alloy has offered significant attention in various material science applications, due to its excellent material features. In this investigation, the mechanical characteristics of Ni2FeCrCuAl High Entropy Alloy (HEA) have been examined under variable temperature and strain rates to analyze its influence over the material features of high entropy alloy through Molecular Dynamics (MD) simulation and it is stated that the formation of various point defects and dislocations are the major cause for the augmentation of tensile deformation which impacts the tensile behavior of high entropy alloy. Moreover, the Radial Distribution Function (RDF) has been examined throughout tensile deformation, to investigate the impact of applied stress over the de-bonding of various atoms and it is found that the strain rate has a greater beneficial impact over the material feature trailed by the temperature outcome, owed to its superior impact on the formation of point defects and shear strain during tensile characterization.

17O-nmr studies of the conformational and dynamic properties of enkephalins in aqueous and organic solutions using selectively labeled analogues

Biopolymers ◽  
1989 ◽  
Vol 28 (1) ◽  
pp. 15-26 ◽  
Author(s):  
Constantinos Sakarellos ◽  
Ioannis P. Gerothanassis ◽  
Nicolaos Birlirakis ◽  
Theodoros Karayannis ◽  
Maria Sakarellos-Daitsiotis ◽  
...  
Keyword(s):  
Dynamic Properties ◽  
Nmr Studies ◽  
17O Nmr ◽  
Organic Solutions

17O NMR studies on dialkoxy disulfides

1998 ◽  
Vol 36 (6) ◽  
pp. 461-462 ◽  
Author(s):  
Giovanni Cerioni ◽  
Antonio Plumitallo
Keyword(s):  
Nmr Studies ◽  
17O Nmr

Chiral "basket handle" binaphthyl porphyrins: synthesis, catalytic epoxidation and NMR conformational studies

2010 ◽  
Vol 14 (07) ◽  
pp. 646-659 ◽  
Author(s):  
Eric Rose ◽  
Emma Gallo ◽  
Nicolas Raoul ◽  
Léa Bouché ◽  
Ariane Pille ◽  
...  
Keyword(s):  
Time Scale ◽  
Room Temperature ◽  
Conformational Equilibrium ◽  
Variable Temperature ◽  
Conformational Exchange ◽  
Iron Catalysts ◽  
Nmr Studies ◽  
Conformational Studies ◽  
H Nmr ◽  
Catalytic Epoxidation

Three "basket handle" porphyrins have been prepared by condensation of tetrakis-(α,β,α,β-2-aminophenyl)porphyrin atropoisomer with 1,1′-binaphthyl, 2,2′-dimethoxy, -3,3′-dicarbonylchloride, -3,3′-diacetylchloride and -3,3′-dipropanoylchloride. The epoxidation of styrene with the three iron catalysts, obtained after metalation of the free porphyrins, occurs with good yields and moderate ee up to 54%. These porphyrins showed unexpected conformational differences, as revealed by NMR spectroscopy. In particular, variable temperature NMR studies showed that the methoxy group in one of them undergoes intermediate conformational exchange on the 1H NMR time scale at room temperature. Lowering the temperature to -50 °C revealed the presence of four states in slow exchange on the NMR time scale. These results evidence a dynamic conformational equilibrium of the binaphthyl handles that adopt different, asymmetric positions with respect to the porphyrin plane.

scholarly journals Variable temperature 1H NMR studies on Grubbs catalysts

2008 ◽  
Vol 693 (7) ◽  
pp. 1252-1260 ◽  
Author(s):  
Margaret M. Gallagher ◽  
A. Denise Rooney ◽  
John J. Rooney
Keyword(s):  
1H Nmr ◽  
Variable Temperature ◽  
Nmr Studies ◽  
Grubbs Catalysts
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