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Quadrupolar Nuclei (quadrupolar + nucleus)
Selected AbstractsThe theory of cosy NMR experiments revisited: Application to an AX spin system of quadrupolar nucleiCONCEPTS IN MAGNETIC RESONANCE, Issue 3 2010P. Kempgens Abstract The two-dimensional nuclear magnetic resonance correlation spectroscopy (2D NMR COSY) spectrum of an AX spin system of spin-1 has been calculated by numerical density matrix calculations. The mathematical expressions found are valid for an AX spin system of any spins. These expressions should be used to calculate the 2D NMR COSY spectrum of an AX spin system of high spin nuclei as their use will significantly simplify the calculations. More precisely, one needs to calculate only one set of coefficients despite the need of two steps in the phase cycling to achieve phase modulation during t1. © 2010 Wiley Periodicals, Inc. Concepts Magn Reson Part A 36A: 170,177, 2010. [source] Structural information from quadrupolar nuclei in solid state NMRCONCEPTS IN MAGNETIC RESONANCE, Issue 3 2006Sharon E. Ashbrook Abstract Solid-state NMR has become the method of choice for determining details of molecular-level structure in heterogeneous systems. Though spin-1/2 nuclei still form the core of most such studies, quadrupolar nuclei are increasingly being used. This review assesses what is currently possible, from achieving high-resolution spectra for quadrupolar nuclei (a prerequisite for most structure determination work), to forming correlation spectra which give qualitative details of spatial proximity of nuclei and the determination of internuclear distances, between quadrupolar spins and quadrupolar and spin-1/2 nuclei. Examples are given of each method discussed, and the advantages and disadvantages of the various experiments for different possible applications are assessed. © 2006 Wiley Periodicals, Inc. Concepts Magn Reson Part A 28A: 183,248, 2006. [source] Two- and three-dimensional multinuclear stray-field imaging of rotating samples with magic-angle spinning (STRAFI-MAS): From bio to inorganic materialsJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 2 2010Alan Wong PhD Abstract Purpose: To revisit and illustrate the potential of a simple and effective multidimensional stray-field imaging technique with magic-angle spinning, known as STRAFI-MAS. Materials and Methods: STRAFI-MAS images are acquired with a standard NMR magnet and a traditional magic-angle sample spinning (MAS) probe. The stray-field gradients are achieved by placing the MAS probe, along the z -direction, at a distance from the center of the magnet. No pulsed-field gradients are applied. The multidimensional spatial encoding is carried out by synchronizing the radiofrequency pulses with the sample MAS rotation. Results: Two-dimensional (2D) and 3D multinuclear images of various phantoms, including a tibia bone and silicon carbide, are recorded. Images of inorganic solids containing quadrupolar nuclei, 23Na and 27Al, are also explored for the first time by STRAFI-MAS. Conclusion: We have demonstrated that STRAFI-MAS is a simple and user-friendly technique for multidimensional imaging without the need of imaging equipment. With the current advancements in NMR and MRI methodologies, STRAFI-MAS is expected to be further developed and improved. We anticipate that STRAFI-MAS can spark a wide spectrum of interest, from material to bio science, where can benefit from high-resolution images. J. Magn. Reson. Imaging 2010;32:418,423. © 2010 Wiley-Liss, Inc. [source] 13C and 15N NMR chemical shifts of 1-(2,,4,-dinitrophenyl) and 1-(2,,4,,6,-trinitrophenyl) pyrazoles in the solid state and in solution,MAGNETIC RESONANCE IN CHEMISTRY, Issue 7 2008M. Ángeles García Abstract The 13C and 15N CPMAS NMR spectra of 18 pyrazoles substituted at position 1 by dinitrophenyl and trinitrophenyl (picryl) groups have been recorded. To help in the assignments, some of these compounds were studied in DMSO- d6 solution. Phenomena such as the conformation of the N -aryl groups and broadening of splittings due to quadrupolar nuclei are discussed. Copyright © 2008 John Wiley & Sons, Ltd. [source] Biomedical applications of 10B and 11B NMRNMR IN BIOMEDICINE, Issue 2 2005Peter Bendel Abstract This review focuses mainly on the detection and investigation of molecules used for boron neutron capture therapy (BNCT) by 10B and 11B NMR. In this binary radiation treatment, boron-containing molecules (also called ,BNCT agents') enriched in the 10B isotope, are targeted to the tumor, and irradiated with thermal or epithermal neutrons. Capture of these neutrons by 10B nuclei generates cell-damaging radiation, confined to single cell dimensions. NMR research efforts have primarily been applied in two directions: first, to investigate the metabolism and pharmaco-kinetics of BNCT agents in-vivo, and second, to use localized NMR spectroscopy and/or MRI for non-invasive mapping of the administered molecules in treated animals or patients. While the first goal can be pursued using 11B NMR for natural-abundance samples (80% 11B / 20% 10B), molecules used in the actual treatment are >,95% enriched in 10B, and must therefore be detected by 10B NMR. Both 10B (spin 3) and 11B (spin 3/2) are quadrupolar nuclei, and their typical relaxation times, in common BNCT agents in biological environments, are rather short. This poses some technical challenges, particularly for MRI, which will be reviewed, along with possible solutions. The first attempts at 11B NMR and MRI detection of BNCT agents in biological tissue were conducted over a decade ago. Since then, results from 11B MRI in laboratory animals and in humans have been reported, and 11B NMR spectroscopy provided interesting and unique information about the metabolism of some BNCT agents in cultured cells. 10B NMR was applied either ,indirectly' (in double-resonance experiments involving coupled protons), but also by direct 10B MRI in mice. However, no results involving the NMR detection of 10B-enriched compounds in treated patients have been reported yet. Copyright © 2005 John Wiley & Sons, Ltd. [source] Probing the Local Structure of Pure Ionic Liquid Salts with Solid- and Liquid-State NMR,CHEMPHYSCHEM, Issue 1 2010Peter G. Gordon Abstract Room-temperature ionic liquids (RTILs) are gaining increasing interest and are considered part of the green chemistry paradigm due to their negligible vapour pressure and ease of recycling. Evidence of liquid-state order, observed by IR and Raman spectroscopy, diffraction studies, and simulated by ab initio methods, has been reported in the literature. Here, quadrupolar nuclei are used as NMR probes to extract information about the solid and possible residual order in the liquid state of RTILs. To this end, the anisotropic nature and field dependence of quadrupolar and chemical shift interactions are exploited. Relaxation time measurements and a search for residual second-order quadrupolar coupling were employed to investigate the molecular motions present in the liquid state and infer what kind of order is present. The results obtained indicate that on a timescale of ,10,8 sec or longer, RTILs behave as isotropic liquids without residual order. [source] | |||||||||||||