13C CHEMICAL SHIFTS OF SOLID (1→4)-α-D-GLUCANS BY CROSS POLARIZATION/MAGIC ANGLE SPINNING (CP/MAS) NMR SPECTROSCOPY. CONFORMATION-DEPENDENT13C CHEMICAL SHIFT AS A REFERENCE IN DETERMINING CONFORMATION IN AQUEOUS SOLUTION

1981 ◽  
Vol 10 (6) ◽  
pp. 713-716 ◽  
Author(s):  
Hazime Saitô ◽  
Ryoko Tabeta
Keyword(s):  
Aqueous Solution ◽  
Nmr Spectroscopy ◽  
Chemical Shift ◽  
Chemical Shifts ◽  
Magic Angle Spinning ◽  
Mas Nmr ◽  
Magic Angle ◽  
Cross Polarization ◽  
Angle Spinning ◽  
Cp Mas Nmr

Chemical reaction of alkoxysilane molecules in wood modified with silanol groups

Holzforschung ◽  
2006 ◽  
Vol 60 (3) ◽  
pp. 271-277 ◽  
Author(s):  
Philippe Tingaut ◽  
Oliver Weigenand ◽  
Carsten Mai ◽  
Holger Militz ◽  
Gilles Sèbe
Keyword(s):  
Nmr Spectroscopy ◽  
Chemical Reaction ◽  
Magic Angle Spinning ◽  
Mas Nmr ◽  
Dibutyltin Dilaurate ◽  
Magic Angle ◽  
Pre Treatment ◽  
Angle Spinning ◽  
Cp Mas Nmr ◽  
Modified Wood

Abstract Chemical reaction between silanol-modified wood and methyltrimethoxysilane (MTMS) was carried out using two different approaches with dibutyltin dilaurate (DBTDL) or ethylamine (EtNH2) as catalysts. Modifications were characterised by Fourier-transform infrared (FTIR) spectroscopy, as well as solid-state 13C and 29Si cross-polarisation with magic-angle spinning nuclear magnetic resonance (CP-MAS NMR) spectroscopy and scanning electron microscopy-energy dispersive X-ray (SEM-EDX) analysis. Silanol-modified wood was obtained by carbamoylation reaction with 3-isocyanatopropyltriethoxysilane (IPTES) and subsequent hydrolysis of the triethoxysilane end groups. 29Si CP-MAS NMR spectroscopy indicated that SiOH groups existed mostly in the form of mono- and di-condensed structures in wood, whatever the level of modification (low or high). The attachment of methyltrimethoxysilane (MTMS) molecules to silanol sites was apparently achieved when ethylamine was used as a catalyst. The reacted MTMS remaining in wood was found to exist mostly in the form of polysiloxane polymers (or oligomers), as shown by 29Si CP-MAS NMR results. Reactions performed with unmodified wood were much less effective, thereby demonstrating the importance of the IPTES pre-treatment.

From Precursors to Non-Oxide Ceramics: Pyrolytic Mechanisms Studied by NMR

1995 ◽  
Vol 410 ◽  
Author(s):  
W. M. Sigmund ◽  
M. Feike ◽  
H. W. Spiess ◽  
F. Aldinger
Keyword(s):  
Magic Angle Spinning ◽  
Mas Nmr ◽  
Inert Gas ◽  
Magic Angle ◽  
Oxide Ceramics ◽  
Cross Polarization ◽  
Chemical Structures ◽  
Angle Spinning ◽  
Cp Mas Nmr ◽  
Probe Head

ABSTRACTThe pyrolysis of a poly ethylsilazane was studied using a CO2-laser beam heated solid state MAS-NMR probe head. Chemical structures of the intermediate stages could be identified. The analogy of the pyrolysis evolution for the following two different methods could be shown: A) in an inert gas furnace conventionally prepared and B) laser irradiated in the NMR probe head under magic-angle spinning (MAS) conditions. Samples prepared by method A were studied by 29Si MAS-NMR and samples prepared by method B were studied with an appropriate cross polarization time by 29Si CP-MAS-NMR. Both experiments showed the same mechanisms for the pyrolysis as the polymer is transformed into a Si3N4/C ceramic.

scholarly journals Sampling Method Affects HR-MAS NMR Spectra of Healthy Caprine Brain Biopsies

Metabolites ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 38
Author(s):  
Annakatrin Häni ◽  
Gaëlle Diserens ◽  
Anna Oevermann ◽  
Peter Vermathen ◽  
Christina Precht
Keyword(s):  
Nmr Spectroscopy ◽  
Sampling Method ◽  
Magic Angle Spinning ◽  
Mas Nmr ◽  
Magic Angle ◽  
1H Nuclear Magnetic Resonance ◽  
Rapid Changes ◽  
Tissue Degradation ◽  
Angle Spinning

The metabolic profiling of tissue biopsies using high-resolution–magic angle spinning (HR-MAS) 1H nuclear magnetic resonance (NMR) spectroscopy may be influenced by experimental factors such as the sampling method. Therefore, we compared the effects of two different sampling methods on the metabolome of brain tissue obtained from the brainstem and thalamus of healthy goats by 1H HR-MAS NMR spectroscopy—in vivo-harvested biopsy by a minimally invasive stereotactic approach compared with postmortem-harvested sample by dissection with a scalpel. Lactate and creatine were elevated, and choline-containing compounds were altered in the postmortem compared to the in vivo-harvested samples, demonstrating rapid changes most likely due to sample ischemia. In addition, in the brainstem samples acetate and inositols, and in the thalamus samples ƴ-aminobutyric acid, were relatively increased postmortem, demonstrating regional differences in tissue degradation. In conclusion, in vivo-harvested brain biopsies show different metabolic alterations compared to postmortem-harvested samples, reflecting less tissue degradation. Sampling method and brain region should be taken into account in the analysis of metabolic profiles. To be as close as possible to the actual situation in the living individual, it is desirable to use brain samples obtained by stereotactic biopsy whenever possible.

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