The two aluminum sites in the 27Al MAS NMR spectrum of kaolinite: Accurate determination of isotropic chemical shifts and quadrupolar interaction parameters

2014 ◽  
Vol 99 (2-3) ◽  
pp. 393-400 ◽  
Author(s):  
M. Paris
Keyword(s):  
Chemical Shifts ◽  
Accurate Determination ◽  
Mas Nmr ◽  
Interaction Parameters ◽  
Quadrupolar Interaction ◽  
Nmr Spectrum ◽  
27Al Mas Nmr ◽  
Isotropic Chemical Shifts

27Al-MAS-NMR-Untersuchungen des thermischen Abbaus von NH4Al(SO4)2·12H2O / 27Al-MAS-NMR Studies on the Thermolysis of NH4Al(SO4)2· 12H2O

1991 ◽  
Vol 46 (11) ◽  
pp. 1515-1518 ◽  
Author(s):  
Gerhard Wegner ◽  
Gert Blumenthal ◽  
Dirk Müller ◽  
Dirk-Henning Menz ◽  
Antje Schmalstieg
Keyword(s):  
Nmr Spectroscopy ◽  
Structural Changes ◽  
Chemical Shifts ◽  
Mas Nmr ◽  
Nmr Studies ◽  
High Stage ◽  
27Al Mas Nmr ◽  
High Resolution Nmr ◽  
First Time

Products of the thermolysis of NH4Al-alum were prepared under dried air and characterized by X-ray powder diffraction, thermogravimetry, and for the first time by solid-state 27Al-MAS-NMR spectroscopy. It was found, that high resolution NMR spectroscopy is applicable to follow up the thermal decomposition and to indicate even minor structural changes. 27Al-MAS-NMR spectra show peaks with characteristic chemical shifts for octahedral Al-units up to a high stage of thermolysis. During the decomposition of Al2(SO4)3 to γ-Al2O3 we again observed three-peak spectra with the specific signal at ≈ 35 ppm for penta-coordinated Al ions as recently proved for the thermolysis of AlCl3 · 6 H2O.

Determination of the Al/Si distribution in synthetic KxMg2Al4+xSi5−xO18 (0< x ⩽1) cordierites by 29Si and 27Al MAS-NMR spectroscopy

1991 ◽  
Vol 26 (18) ◽  
pp. 5053-5059 ◽  
Author(s):  
J. Senegas ◽  
A. R. Grimmer ◽  
D. Muller ◽  
P. Thomas ◽  
D. Mercurio ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
Mas Nmr ◽  
27Al Mas Nmr

23Na 2D 3QMAS NMR and 29Si, 27Al MAS NMR investigation of Laponite and synthetic saponites of variable interlayer charge

Clay Minerals ◽  
2003 ◽  
Vol 38 (1) ◽  
pp. 63-69 ◽  
Author(s):  
L. Delevoye ◽  
J . -L. Robert ◽  
J . Grandjean
Keyword(s):  
High Resolution ◽  
Chemical Shift ◽  
Chemical Analysis ◽  
Nmr Spectra ◽  
Mas Nmr ◽  
High Resolution Spectrum ◽  
Isotropic Chemical Shift ◽  
Quadrupolar Interaction ◽  
27Al Mas Nmr ◽  
Good Agreement

Abstract29Si, 27Al MAS NMR is used to characterize Laponite RD and synthetic saponites of variable interlayer charge. The Si/Al ratios are in good agreement with the calculated charge from chemical analysis except for the lowest-charged saponite. In contrast to the 29Si MAS NMR spectra in which resolved signals are detected, the 27Al MAS NMR spectra show one signal whose linewidth increases with the clay charge. The water content of the clay samples was obtained from 1H MAS NMR.The 2D MQMAS NMR technique is required to obtain a high-resolution spectrum of nuclei with strong quadrupolar interaction. This method was applied to the 23Na nucleus of clay counterions and to the 27Al structural nucleus. One well-defined 23Na NMR signal is observed for all the clays studied except the highest-charged saponite. Possible explanations for this different behaviour are discussed. The calculated isotropic chemical shift evolves progressively with the clay charge whereas the deduced quadrupolar interaction does not change significantly. The 27Al 2D 3QMAS technique was not able to resolve more than one signal.

scholarly journals Rapid and accurate determination of atomistic RNA dynamic ensemble models using NMR and structure prediction

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Honglue Shi ◽  
Atul Rangadurai ◽  
Hala Abou Assi ◽  
Rohit Roy ◽  
David A. Case ◽  
...  
Keyword(s):  
Structure Prediction ◽  
Residual Dipolar Couplings ◽  
Chemical Shifts ◽  
Accurate Determination ◽  
Rna Structures ◽  
Atomic Structures ◽  
Data Gap ◽  
Nmr Residual Dipolar Couplings ◽  
And Function

Abstract Biomolecules form dynamic ensembles of many inter-converting conformations which are key for understanding how they fold and function. However, determining ensembles is challenging because the information required to specify atomic structures for thousands of conformations far exceeds that of experimental measurements. We addressed this data gap and dramatically simplified and accelerated RNA ensemble determination by using structure prediction tools that leverage the growing database of RNA structures to generate a conformation library. Refinement of this library with NMR residual dipolar couplings provided an atomistic ensemble model for HIV-1 TAR, and the model accuracy was independently supported by comparisons to quantum-mechanical calculations of NMR chemical shifts, comparison to a crystal structure of a substate, and through designed ensemble redistribution via atomic mutagenesis. Applications to TAR bulge variants and more complex tertiary RNAs support the generality of this approach and the potential to make the determination of atomic-resolution RNA ensembles routine.

Progress in Structural Elucidation of Glasses by and 1B Satellite Transition NMR Spectroscopy

1995 ◽  
Vol 50 (4-5) ◽  
pp. 413-422 ◽  
Author(s):  
G. Kunath-Fandrei ◽  
D. Ehrt ◽  
C. Jäger
Keyword(s):  
Nmr Spectroscopy ◽  
Quadrupole Interaction ◽  
Chemical Shifts ◽  
Glass Structure ◽  
Structural Elucidation ◽  
Mas Nmr ◽  
Interaction Parameters ◽  
31P Mas Nmr ◽  
Satellite Transition

The structure of Na2O-Al2O3-B2O3 and Na2O-Al2O3-P2O5 glasses with 70 mole% B2O3 or P2O5 and varied Na/Al ratio is investigated using standard 31P MAS NMR and 27Al and UB Satellite Transition NMR spectroscopy. The role of the two network formers on the glass structure is discussed. For the AlOx units and BO3 and BO4 groups both chemical shifts and quadrupole interaction parameters including their distribution widths are reported. Besides this, the advantages of Satellite Transition spectroscopy are demonstrated both for 27A1 and 11B NMR

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