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Solid State Nuclear Magnetic Resonance

Gregory Lusk, Terry Gullion
Some MAS NMR experiments are sensitive to fluctuations or drifts in rf field strengths. We examine the simple 1H-13C CPMAS experiment and show that the 13C signal intensities vary over time due to drifts in rf field strengths. The causes of the drifts in rf field strengths are studied. Stabilization of the rf field strengths are obtained by using an rf field-strength controller. The controller is a stand-alone unit, which can be easily incorporated in any spectrometer system. Details of the controller, including circuit design, are provided...
February 3, 2018: Solid State Nuclear Magnetic Resonance
Kaustubh R Mote, Perunthiruthy K Madhu
We show here an effective way of implementing simultaneously homonuclear and heteronuclear dipolar decoupling in magic-angle spinning (MAS) solid-state NMR. Whilst the homonuclear spin decoupling is applied on the 1H channel, heteronuclear spin decoupling is applied on the 13C channel. The 1H spins are observed in a windowed fashion in this case. The resultant 1H spectrum has higher resolution due to the attenuation of broadening arising from both homonuclear 1H-1H and heteronuclear 1H-13C interactions, with the latter normally leading to additional line broadening in 13C labelled samples...
January 20, 2018: Solid State Nuclear Magnetic Resonance
A M Panich, N A Sergeev, M Paczwa, M Olszewski
No abstract text is available yet for this article.
January 3, 2018: Solid State Nuclear Magnetic Resonance
Shenhui Li, Jing Li, Jing Tang, Feng Deng
Solid-state NMR was utilized to explore the host-guest interaction between adsorbate and adsorbent at atomic level to understand the separation mechanism of styrene (St) and ethylbenzene (EB) in MIL-53(Al). 13C-27Al double-resonance NMR experiments revealed that the host-guest interaction between St and MIL-53 was much stronger than that of EB adsorption. In addition, 13C DIPSHIFT experiments suggested that the adsorbed St was less mobile than EB confined inside the MIL-53 pore. Furthermore, the host-guest interaction model between St, EB and MIL-53 was established on the basis of the spatial proximities information extracted from 2D 1H-1H homo-nuclear correlation NMR experiments...
December 29, 2017: Solid State Nuclear Magnetic Resonance
Jaclyn Catalano, Anna Murphy, Yao Yao, Nicholas Zumbulyadis, Silvia A Centeno, Cecil Dybowski
Many oil paintings, dating from the 15th century to the present, are affected by the formation of heavy-metal carboxylates (soaps) that alter the structural integrity and appearance of the works. Through transport phenomena not yet understood, free fatty acids formed from oils used as binders migrate through the paint film and react with heavy-metal ions that are constituents of pigments and/or driers, forming metal carboxylates. The local molecular dynamics of fatty acids and metal carboxylates are factors influencing material transport in these systems...
December 22, 2017: Solid State Nuclear Magnetic Resonance
Otto E O Zeman, Constantin Hoch, Rupert Hochleitner, Thomas Bräuniger
Orientation-dependent NMR spectra of a single crystal of the mineral vanadinite, Pb5(VO4)3Cl, were acquired using only one rotation axis with a general orientation in the hexagonal crystal lattice (space group P63/m). The chemical shift (CS) tensors for the 207Pb on Wyckoff positions 6h and 4f, and both CS and quadrupole coupling tensor Q for 51V at the positions 6h were determined by including the NMR response of symmetry-related atoms in the unit cell (and in case of 207Pb at 4f, also the isotropic shift from MAS NMR spectra)...
December 8, 2017: Solid State Nuclear Magnetic Resonance
Kong Ooi Tan, Vipin Agarwal, Nils-Alexander Lakomek, Susanne Penzel, Beat H Meier, Matthias Ernst
Through-bond J-coupling based experiments in solid-state NMR spectroscopy are challenging because the J couplings are typically much smaller than the dipolar couplings. This often leads to a lower transfer efficiency compared to dipolar-coupling based sequences. One of the reasons for the low transfer efficiency are the second-order cross terms involving the strong heteronuclear dipolar couplings leading to fast magnetization decay. Here, we show that by employing a symmetry-based C9 sequence, which was carefully selected to suppress second-order terms, efficient polarization transfers of up to 80% can be achieved without decoupling on fully protonated two-spin model systems at a MAS frequency of 55...
December 5, 2017: Solid State Nuclear Magnetic Resonance
Abil E Aliev, Albert P Bartók, Jonathan R Yates
Two different axial symmetries of the 119Sn chemical shift anisotropy (CSA) in tin dioxide with the asymmetry parameter (η) of 0 and 0.27 were reported previously based on the analysis of MAS NMR spectra. By analyzing the static powder pattern, we show that the 119Sn CSA is axially symmetric. A nearly axial symmetry and the principal axis system of the 119Sn chemical shift tensor in SnO2 were deduced from periodic scalar-relativistic density functional theory (DFT) calculations of NMR parameters. The implications of fast small-angle motions on CSA parameters were also considered, which could potentially lead to a CSA symmetry in disagreement with a crystal symmetry...
November 28, 2017: Solid State Nuclear Magnetic Resonance
Eva Meirovitch, Zhichun Liang, Jack H Freed
We report on a new approach to the analysis of dynamic NMR lineshapes from polycrystalline (i.e., macroscopically disordered) samples in the presence of Magic Angle Spinning (MAS). This is an application of the Stochastic Liouville Equation developed by Freed and co-workers for treating restricted (i.e., microscopically ordered) motions. The 2H nucleus in an internally-mobile C-CD3 moiety serves as a prototype probe. The acronym is 2H/MOMD/MAS, where MOMD stands for "microscopic-order-macroscopic-disorder." The key elements describing internal motions - their type, the local spatial restrictions, and related features of local geometry - are treated in MOMD generally, within their rigorous three-dimensional tensorial requirements...
November 21, 2017: Solid State Nuclear Magnetic Resonance
Alexander C Forse, John M Griffin, Clare P Grey
Nuclear magnetic resonance (NMR) spectroscopy has emerged as a useful technique for probing the structure and dynamics of the electrode-electrolyte interface in supercapacitors, as ions inside the pores of the carbon electrodes can be studied separately from bulk electrolyte. However, in some cases spectral resolution can limit the information that can be obtained. In this study we address this issue by showing how cross polarisation (CP) NMR experiments can be used to selectively observe the in-pore ions in supercapacitor electrode materials...
November 4, 2017: Solid State Nuclear Magnetic Resonance
Gregory S Boutis, Ravinath Kausik
Quantitative evaluation of the solid and viscous components of unconventional shale rock, namely kerogen and bitumen, is important for understanding reservoir quality. Short transverse coherence times, due to strong (1)H-(1)H dipolar interactions, motivates the application of solid state refocusing pulse sequences that allow for investigating components of the free-induction decay that are otherwise obscured by instrumental effects such as probe ringdown. This work reports on static, wide-line (1)H spectroscopy of shale rock and their extracted components, which include kerogen and bitumen, by the application of solid echo and magic echo pulse sequences...
November 3, 2017: Solid State Nuclear Magnetic Resonance
Shigenobu Hayashi, Keiko Jimura
Inorganic solid acid salts with hydrogen bond networks frequently show very long spin-lattice relaxation times even for (1)H because the hydrogen bonds suppress motions. In the present work, the (1)H spin-lattice relaxation in Cs2(HSO4)(H2PO4) containing a small amount of ammonium ions were studied in detail by use of the effect of magic angle spinning (MAS) on the relaxation. The (1)H spin-lattice relaxation times of the acid protons decrease with increase in the content of ammonium ions. Reorientation of the NH4 group fluctuates the dipole-dipole interaction and relaxes the ammonium protons as well as the acid protons...
November 2, 2017: Solid State Nuclear Magnetic Resonance
Patrick C A van der Wel
The aggregation of proteins and peptides into a variety of insoluble, and often non-native, aggregated states plays a central role in many devastating diseases. Analogous processes undermine the efficacy of polypeptide-based biological pharmaceuticals, but are also being leveraged in the design of biologically inspired self-assembling materials. This Trends article surveys the essential contributions made by recent solid-state NMR (ssNMR) studies to our understanding of the structural features of polypeptide aggregates, and how such findings are informing our thinking about the molecular mechanisms of misfolding and aggregation...
October 4, 2017: Solid State Nuclear Magnetic Resonance
Marek J Potrzebowski
No abstract text is available yet for this article.
October 2017: Solid State Nuclear Magnetic Resonance
Diego F Gauto, Audrey Hessel, Petra Rovó, Vilius Kurauskas, Rasmus Linser, Paul Schanda
Solid-state NMR spectroscopy can provide site-resolved information about protein dynamics over many time scales. Here we combine protein deuteration, fast magic-angle spinning (~45-60kHz) and proton detection to study dynamics of ubiquitin in microcrystals, and in particular a mutant in a region that undergoes microsecond motions in a β-turn region in the wild-type protein. We use (15)N R1ρ relaxation measurements as a function of the radio-frequency (RF) field strength, i.e. relaxation dispersion, to probe how the G53A mutation alters these dynamics...
October 2017: Solid State Nuclear Magnetic Resonance
Scott Sneddon, Jürgen Kahr, Angelica F Orsi, David J Price, Daniel M Dawson, Paul A Wright, Sharon E Ashbrook
Zeolitic imidazolate frameworks (ZIFs) are a subclass of metal-organic frameworks (MOFs) with extended three-dimensional networks of transition metal nodes (bridged by rigid imidazolate linkers), with potential applications in gas storage and separation, sensing and controlled delivery of drug molecules. Here, we investigate the use of (13)C and (15)N solid-state NMR spectroscopy to characterise the local structure and disorder in a variety of single- and dual-linker ZIFs. In most cases, a combination of a basic knowledge of chemical shifts typically observed in solution-state NMR spectroscopy and the use of dipolar dephasing NMR experiments to reveal information about quaternary carbon species are combined to enable spectral assignment...
September 9, 2017: Solid State Nuclear Magnetic Resonance
Y Nishiyama, M Malon, M J Potrzebowski, P Paluch, J P Amoureux
No abstract text is available yet for this article.
September 1, 2017: Solid State Nuclear Magnetic Resonance
Xiaoyue Zhou, Kaipin Xu, Pei Ni, Qun Chen, Shanmin Zhang
Most of the polymers are composed of a crystal part, an amorphous part, and a transitional interfacial part. These components present disparate physical and chemical characteristics. However, it always suffers from peak overlapping in solid NMR spectrum in order to acquire polymer's crystallinity. The polyethylene oxide (PEO) sample was tested using the Torchia pulse sequence combined with the Multivariate Curve Resolution (MCR) method. A two dimensional CP/MAS spectrum containing spin-lattice relaxation time (T1) information was acquired...
September 2017: Solid State Nuclear Magnetic Resonance
Christophe Odin
In NMR, the repetition of pulse sequences with a recycle time that does not allow the spin system to completely relax back to equilibrium is a well known and often used method to increase the signal to noise ratio at given total measuring time. For isolated spins I=1/2, the steady-state of a train of strictly identical pulse sequences separated by free evolution periods of same duration is described by the well known Ernst-Anderson model, and the optimum pulse angle is given by the Ernst angle. We showed recently that equivalent formula, but with super-operators in the Liouville space, can be obtained for general spins I...
September 2017: Solid State Nuclear Magnetic Resonance
Paul Jonsen
During August 2015, the author surveyed 76 solid state NMR scientists from materials science to biology, academic to industrial, based in North America, Europe, India, China, Japan and Australia. The subject concerned barriers to the wider acceptance of solid state NMR and included the various barriers based on experimental, funding, vendor based and community aspects. This survey was confidential. However, many of the survey participants requested that at least the results of the part of the survey relevant to our community be made public...
September 2017: Solid State Nuclear Magnetic Resonance
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