scholarly journals Chain Trajectory, Chain Packing, and Molecular Dynamics of Semicrystalline Polymers as Studied by Solid-State NMR

Polymers ◽  
2018 ◽  
Vol 10 (7) ◽  
pp. 775 ◽  
Author(s):  
Shijun Wang ◽  
You-Lee Hong ◽  
Shichen Yuan ◽  
Wei Chen ◽  
Wenxuan Zhou ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Level Structure ◽  
Semicrystalline Polymers ◽  
Double Quantum ◽  
Melt Crystallization ◽  
Nmr Studies ◽  
Packing Structure ◽  
Past Half Century ◽  
Nucleation Mechanisms ◽  
Chain Level

Chain-level structure of semicrystalline polymers in melt- and solution-grown crystals has been debated over the past half century. Recently, 13C–13C double quantum (DQ) Nuclear Magnetic Resonance (NMR) spectroscopy has been successfully applied to investigate chain-folding (CF) structure and packing structure of 13C enriched polymers after solution and melt crystallization. We review recent NMR studies for (i) packing structure, (ii) chain trajectory, (iii) conformation of the folded chains, (iv) nucleation mechanisms, (v) deformation mechanism, and (vi) molecular dynamics of semicrystalline polymers.

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.

Hydrogen Storage in MgH2 Matrices: An Ab-Initio Study of Mg-MgH2 Interface

2008 ◽  
Vol 139 ◽  
pp. 23-28 ◽  
Author(s):  
Simone Giusepponi ◽  
Massimo Celino ◽  
Fabrizio Cleri ◽  
Amelia Montone
Keyword(s):  
Molecular Dynamics ◽  
Total Energy ◽  
Ab Initio ◽  
Atomic Hydrogen ◽  
Level Structure ◽  
Atomic Level ◽  
Work Of Adhesion ◽  
Ab Initio Study ◽  
Dynamics Method ◽  
Good Agreement

We studied the atomic-level structure of a model Mg-MgH2 interface by means of the Car-Parrinello molecular dynamics method (CPMD). The interface was characterized in terms of total energy calculations, and an estimate of the work of adhesion was given, in good agreement with experimental results on similar systems. Furthermore, the interface was studied in a range of temperatures of interest for the desorption of hydrogen. We determined the diffusivity of atomic hydrogen as a function of the temperature, and give an estimate of the desorption temperature.

Double-quantum 1 H NMR studies of nitrogen metabolism in yeast

FEBS Letters ◽  
1984 ◽  
Vol 178 (1) ◽  
pp. 123-126 ◽  
Author(s):  
Hans Paul Juretschke
Keyword(s):  
Nitrogen Metabolism ◽  
Double Quantum ◽  
Nmr Studies ◽  
H Nmr

scholarly journals Exploring Dynamics and Structure of Biomolecules, Cryoprotectants, and Water Using Molecular Dynamics Simulations: Implications for Biostabilization and Biopreservation

2019 ◽  
Vol 21 (1) ◽  
pp. 1-31 ◽  
Author(s):  
Lindong Weng ◽  
Shannon L. Stott ◽  
Mehmet Toner
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Molecular Motion ◽  
State Of The Art ◽  
Level Structure ◽  
Cost Effective ◽  
Atomic Level ◽  
Computational Research ◽  
Dynamics Simulations ◽  
Biological Entities

Successful stabilization and preservation of biological materials often utilize low temperatures and dehydration to arrest molecular motion. Cryoprotectants are routinely employed to help the biological entities survive the physicochemical and mechanical stresses induced by cold or dryness. Molecular interactions between biomolecules, cryoprotectants, and water fundamentally determine the outcomes of preservation. The optimization of assays using the empirical approach is often limited in structural and temporal resolution, whereas classical molecular dynamics simulations can provide a cost-effective glimpse into the atomic-level structure and interaction of individual molecules that dictate macroscopic behavior. Computational research on biomolecules, cryoprotectants, and water has provided invaluable insights into the development of new cryoprotectants and the optimization of preservation methods. We describe the rapidly evolving state of the art of molecular simulations of these complex systems, summarize the molecular-scale protective and stabilizing mechanisms, and discuss the challenges that motivate continued innovation in this field.

Solid-state NMR studies of the molecular dynamics and phase behavior of mixed-chain phosphatidylcholines

Biochemistry ◽  
1984 ◽  
Vol 23 (9) ◽  
pp. 1988-1993 ◽  
Author(s):  
B. A. Lewis ◽  
S. K. Das Gupta ◽  
R. G. Griffin
Keyword(s):  
Molecular Dynamics ◽  
Solid State ◽  
Phase Behavior ◽  
Solid State Nmr ◽  
Nmr Studies

Molecular dynamics and NMR studies of single-stranded PNAs

1994 ◽  
Vol 35 (29) ◽  
pp. 5105-5108 ◽  
Author(s):  
Shiow-Meei Chen ◽  
Venkatraman Mohan ◽  
John S Kiely ◽  
Michael C. Griffith ◽  
Richard H. Griffey
Keyword(s):  
Molecular Dynamics ◽  
Nmr Studies
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