scholarly journals Flexibility at a glycosidic linkage revealed by molecular dynamics, stochastic modeling, and 13C NMR spin relaxation: conformational preferences of α-l-Rhap-α-(1 → 2)-α-l-Rhap-OMe in water and dimethyl sulfoxide solutions

2016 ◽  
Vol 18 (4) ◽  
pp. 3086-3096 ◽  
Author(s):  
Robert Pendrill ◽  
Olof Engström ◽  
Andrea Volpato ◽  
Mirco Zerbetto ◽  
Antonino Polimeno ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Stochastic Modeling ◽  
Spin Relaxation ◽  
13C Nmr ◽  
Nmr Relaxation ◽  
Glycosidic Linkage ◽  
Local Motion ◽  
Flexible Molecule ◽  
Relaxation Parameters ◽  
Conformational Preferences

Coupling between global reorientation and local motion is essential for reproducing NMR relaxation parameters of a flexible molecule.

scholarly journals Differential Dynamics at Glycosidic Linkages of an Oligosaccharide as Revealed by 13C NMR Spin Relaxation and Stochastic Modeling

2018 ◽  
Vol 122 (8) ◽  
pp. 2287-2294 ◽  
Author(s):  
Mirco Zerbetto ◽  
Thibault Angles d’Ortoli ◽  
Antonino Polimeno ◽  
Göran Widmalm
Keyword(s):  
Stochastic Modeling ◽  
Spin Relaxation ◽  
13C Nmr ◽  
Nmr Spin Relaxation

Global and internal molecular dynamics of poly(acrylamide-co-allyl 2-acetamido-2-deoxy-D-glucopyranoside) glycopolymers from 13C NMR relaxation studies

1993 ◽  
Vol 71 (12) ◽  
pp. 1995-2006 ◽  
Author(s):  
René Roy ◽  
François D. Tropper ◽  
Antony J. Williams ◽  
Jean-Robert Brisson
Keyword(s):  
Molecular Dynamics ◽  
Spin Relaxation ◽  
Correlation Time ◽  
Relaxation Times ◽  
Nmr Relaxation ◽  
Relaxation Rates ◽  
Polymer Backbone ◽  
Model Free ◽  
Internal Motions ◽  
Poly Acrylamide

13C spin-lattice and spin–spin relaxation times and nuclear Overhauser enhancements have been used to examine the molecular dynamics of the α- (1) and β- (2) anomeric forms of poly(acrylamide-co-allyl 2-acetamido-2-deoxy-D-glucopyranoside) glycopolymers. The timescale of motions and the spatial restriction of these motions were determined by using various forms of the "model-free" approach. It is shown that the motions of the C—H vectors of the polymer backbone may be described by a scaled Lorentzian spectral density function, giving rise to an effective correlation time for overall tumbling. The temperature dependence of this correlation time suggests that the overall motion is dependent on viscosity. The overall motion of the polymer molecules is shown to be anisotropic in nature by including the spin–spin relaxation data in the analysis. The N-acetyl methyl and sugar hydroxymethyl (C6) groups exhibit internal motions. The activation energies associated with these internal motions are derived. The difference in relaxation rates between the α and β anomeric forms, though small, suggests that the motions of the sugar ring may be different for the two systems. This conclusion is supported by potential energy contour map calculations, which indicate that the β anomer (2) has almost twice the conformational flexibility of the α anomer (1).

Structure and Dynamics of Spherical and Rodlike Alkyl Ethoxylate Surfactant Micelles Investigated Using NMR Relaxation and Atomistic Molecular Dynamics Simulations

2019 ◽  
Author(s):  
Allison Edwards ◽  
Abdolreza Javidialesaadi ◽  
Katie Weigandt ◽  
George Stan ◽  
Charles Eads
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Nmr Relaxation ◽  
Cross Relaxation ◽  
Relaxation Rates ◽  
Surfactant Micelles ◽  
Cylindrical Micelles ◽  
Spherical Micelles ◽  
Dynamics Simulations ◽  
Relative Motions

We study molecular arrangements and dynamics in alkyl ethoxylate nonionic surfactant micelles by combining high field (600 and 700 MHz) NMR relaxation measurements with large-scale atomistic molecular dynamics simulations. For spherical micelles, but not for cylindrical micelles, cross relaxation rates are positive only for surfactant alkyl tail atoms connected to the hydrophilic head group. All cross relaxation rates are negative for cylindrical micelles. This effect is reproducible either by changing composition (ratios of the nonionic surfactants) or changing temperature of a single surfactant in order to change the micelle shape. We validate the micelle shape by SANS and use the results as a guide for our simulations. We calculate parameters that determine relaxation rates directly from simulated trajectories, without introducing specific functional forms. Results indicate that relative motions of nearby atoms are liquid-like, in agreement with 13C T1 measurements, though constrained by micelle morphology. Relative motions of distant atoms have slower components because the relative changes in distances and angles are smaller when the moving atoms are further apart. The slow, long-range motions appear to be responsible for the predominantly negative cross relaxation rates observed in NOESY spectra. The densities of atoms from positions 1 and 2 in the boundary region are lower in spherical micelles compared to cylindrical micelles. Correspondingly, motions in this region are less constrained by micelle morphology in the spherical compared to the cylindrical cases. The two effects of morphology lead to the unusual occurrence of positive cross relaxation involving positions 1 and 2 for spheres.

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