Structural units in humic acids from south-eastern Queensland soils as determined by 13nmr spectroscopy

Soil Research ◽  
1983 ◽  
Vol 21 (4) ◽  
pp. 539 ◽  
Author(s):  
JO Skjemstad ◽  
RL Frost ◽  
PF Barron
Keyword(s):  
Humic Acids ◽  
Significant Proportion ◽  
Building Blocks ◽  
Magic Angle Spinning ◽  
Total Carbon ◽  
Magic Angle ◽  
Major Contributor ◽  
Nmr Spectrum ◽  
Two Samples ◽  
Angle Spinning

Solution 13C Fourier transform nuclear magnetic resonance (FTNMR) spectra of six humic acids extracted from a range of soil types and a solid state, cross polarization/magic angle spinning (CP/ MAS) 13C NMR spectrum of a lignin are reported. Quantifying specific regions of the spectra reveals the presence of alkyl, carbohydrate, aromatic and carboxyl carbons. Alkyl carbon is in general the major contributor to these spectra, averaging 38% of the total carbon. Long-chain units comprise a significant proportion of this group, although highly branched systems are also in evidence in two samples. Carbohydrate carbon is a major contributor in two samples, representing 27% and 28% of the total carbon nuclei measured. Aromatic carbon content shows the greatest variability, ranging from 10 to 45%. Humic acids from soils developed under rainforest show the lowest aromaticity, and it is suggested that aromatic structures are not integral building blocks of terrestrial humic acids. Little evidence was found for the presence of hydroxy- and methoxy-substituted aromatic carbons even in humic acids high in aromaticity.

scholarly journals Dynamic regulation of HIV-1 capsid interaction with the restriction factor TRIM5α identified by magic-angle spinning NMR and molecular dynamics simulations

2018 ◽  
Vol 115 (45) ◽  
pp. 11519-11524 ◽  
Author(s):  
Caitlin M. Quinn ◽  
Mingzhang Wang ◽  
Matthew P. Fritz ◽  
Brent Runge ◽  
Jinwoo Ahn ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Building Blocks ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
Capsid Assembly ◽  
Dynamic Regulation ◽  
Angle Spinning ◽  
Dynamics Simulations ◽  
Hiv 1

The host factor protein TRIM5α plays an important role in restricting the host range of HIV-1, interfering with the integrity of the HIV-1 capsid. TRIM5 triggers an antiviral innate immune response by functioning as a capsid pattern recognition receptor, although the precise mechanism by which the restriction is imposed is not completely understood. Here we used an integrated magic-angle spinning nuclear magnetic resonance and molecular dynamics simulations approach to characterize, at atomic resolution, the dynamics of the capsid’s hexameric and pentameric building blocks, and the interactions with TRIM5α in the assembled capsid. Our data indicate that assemblies in the presence of the pentameric subunits are more rigid on the microsecond to millisecond timescales than tubes containing only hexamers. This feature may be of key importance for controlling the capsid’s morphology and stability. In addition, we found that TRIM5α binding to capsid induces global rigidification and perturbs key intermolecular interfaces essential for higher-order capsid assembly, with structural and dynamic changes occurring throughout the entire CA polypeptide chain in the assembly, rather than being limited to a specific protein-protein interface. Taken together, our results suggest that TRIM5α uses several mechanisms to destabilize the capsid lattice, ultimately inducing its disassembly. Our findings add to a growing body of work indicating that dynamic allostery plays a pivotal role in capsid assembly and HIV-1 infectivity.

Solid State 13C NMR Applied to Styrene-Butadiene Rubbers Study of the Rubber Vulcanized Network Structures

2002 ◽  
Vol 75 (1) ◽  
pp. 65-76 ◽  
Author(s):  
L. Pellicioli ◽  
S. K. Mowdood ◽  
F. Negroni ◽  
D. D. Parker ◽  
J. L. Koenig
Keyword(s):  
13C Nmr ◽  
Structural Changes ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
Nmr Spectrum ◽  
Polymer Microstructure ◽  
Polybutadiene Rubber ◽  
Angle Spinning ◽  
Styrene Butadiene

Abstract This paper discusses the structural changes that occur during the accelerated sulfur vulcanization of styrene-butadiene rubbers (SBR) through characterization of the network sulfide structures influenced by the curing agent concentration, the polymer microstructure, and the nature of the filler. Magic angle spinning (MAS) 13C FT - NMR spectroscopy was used to investigate the chemical crosslink properties of unfilled vulcanized SBR in addition to carbon black and silica filled polybutadiene rubber (BR), SBR, and 1:1 BR / SBR blends. New resonances in the 13C NMR spectrum are assigned to the various sulfide crosslink structures in SBR. Structural changes during vulcanization are also discussed.

scholarly journals Aspects of solid state 13C CPMAS NMR spectroscopy in coals from the Balkan peninsula

2003 ◽  
Vol 68 (8-9) ◽  
pp. 599-606 ◽  
Author(s):  
Andreas Georgakopoulos
Keyword(s):  
Bituminous Coal ◽  
Balkan Peninsula ◽  
Magic Angle Spinning ◽  
Paramagnetic Species ◽  
Magic Angle ◽  
Northern Greece ◽  
13C Cpmas Nmr ◽  
Nmr Spectrum ◽  
Serbia And Montenegro ◽  
Angle Spinning

The cross-polarized magic-angle-spinning NMR (CPMAS-NMR) technique was used in this work to assess the carbon distribution in coals of different rank (peat, lignite, xylite, sub-bituminous coal) from important deposits in Greece and Bulgaria. The technique is assumed to be only semiquantitative due to a number of interferences, such as spinning side bands (SSB) in the spectra, paramagnetic species in the samples, and low or remote protonation of aromatic carbons. The Bulgarian sub-bituminous coal shows the greatest amounts of aromatic structures. The lignite sample from the Drama basin Northern Greece, is relatively unaltered and largely unlettered, and shows the greatest amounts of aliphatic groups. The 13C-NMR spectra of Pliocene lignites from endemic areas in Serbia and Montenegro and Bosnia, taken from published papers, show significantly more intense resonance's for methoxyl phenolic, and polysaccharide moieties compared to the Drama lignite NMR spectrum. Xylite reveals high contents of carbohydrates.

Synthesis of amorphous boron nitride from the molecular precursor ammonia-monochloroborane

1999 ◽  
Vol 14 (5) ◽  
pp. 1934-1938 ◽  
Author(s):  
Douglas R. Ketchum ◽  
Allison L. DeGraffenreid ◽  
Philipp M. Niedenzu ◽  
Sheldon G. Shore
Keyword(s):  
Xrd Analysis ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
Gas Evolution ◽  
Amorphous Boron ◽  
X Ray Diffraction ◽  
Nmr Spectrum ◽  
X Ray ◽  
Molecular Precursor ◽  
Angle Spinning

Ammonia-monochloroborane, NH3BH2Cl, has been synthesized from the reaction of ammonia-borane with HCl in Et2O. Decomposition of the solid under NH3 to 600 °C produced amorphous BN in 97% yield. The 11B magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectrum of the amorphous BN is indicative of boron in the same environment as in hexagonal BN. Subsequent pyrolysis of the amorphous BN to 1000 °C produced turbostratic BN. Pyrolysis of NH3BH2Cl under vacuum to 1100 °C led to the formation of turbostratic BN as confirmed by x-ray diffraction (XRD) analysis. Gas evolution during this pyrolysis confirmed that the precursor loses H2 and HCl.

scholarly journals Paramagnetic 14N MAS NMR without Paramagnetic Shifts: Remarkable Lattice of LaTiO2N and CeTiO2N Oxynitride Perovskites

2020 ◽  
Author(s):  
Zili Ma ◽  
Richard Dronskowski ◽  
Adam Slabon ◽  
Aleksander Jaworski
Keyword(s):  
Solid Material ◽  
Magic Angle Spinning ◽  
Mas Nmr ◽  
Magic Angle ◽  
Molecular Orbital Calculations ◽  
Nmr Spectrum ◽  
H Nmr ◽  
Contact Shift ◽  
Angle Spinning ◽  
Paramagnetic Shifts

<sup>14</sup>N magic-angle spinning (MAS) NMR spectra of diamagnetic LaTiO<sub>2</sub>N perovskite oxynitride and its paramag-<br>netic counterpart CeTiO<sub>2</sub>N are presented. The latter, to the<br>best of our knowledge, constitutes the first high-resolution <sup>14</sup>N MAS NMR spectrum collected from paramagnetic solid material. Induced paramagnetic <sup>14</sup>N NMR shift due to unpaired 4<i>f</i> -electrons in CeTiO<sub>2</sub>N is non-existent, which is remarkable given the severe paramagnetic effects on surface proton species revealed by <sup>1</sup>H NMR, and direct Ce−N contacts in the structure. <i>Ab initio</i> molecular orbital calculations predict substantial Ce→<sup>14</sup>N contact shift interaction under these circumstances, therefore, cannot explain the unprecedented <sup>14</sup>N NMR spectrum of CeTiO<sub>2</sub>N.

Quantitative Analysis of Vulcanized SBR/EPDM Diblends. Magic Angle Spinning 13C-NMR Experiments at 80°C

1990 ◽  
Vol 63 (2) ◽  
pp. 215-222 ◽  
Author(s):  
G. P. M. van der Velden ◽  
J. Kelm
Keyword(s):  
13C Nmr ◽  
Solid State Nmr ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
Nmr Spectrum ◽  
Blend Ratio ◽  
Quantitative Expression ◽  
Angle Spinning ◽  
Co Addition ◽  
Styrene Butadiene

Abstract A new quantitative expression has been derived in order to estimate the styrene-butadiene ratio from the 13C-NMR olefinic resonances. With the help of this expression, the cis-1,4, trans-1,4, vinyl-1,2, butadiene and styrene ratios could be determined. From the aliphatic region, subsequently, the ethylene and propylene contents could be determined and finally the SBR/EPDM blend ratio. From the 13C-solid-state-NMR spectrum, no evidence could be obtained for homo- or co-vulcanization. The 13C-NMR spectra of the blends are simply a co-addition of the 13C-NMR solution spectra of SBR and EPDM rubbers. No evidence has been found for cis-1,4/trans-1,4 ratio changes for SBR (in comparison to the starting material).

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