Double-quantum filtered volume-selective NMR spectroscopy (original) (raw)
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Localized double-quantum-filtered 1 H NMR spectroscopy
The image-guided in vivo spectroscopic (ISIS) pulse sequence has been combined with a double-quantum-filter scheme in order to obtain localized and water-suppressed 'H NMR spectra of J-coupled metabolites. The coherence-transfer efficiency associated with the DQ filter for AX and ASX spin systems is described. Phantom results of carnosine, alanine, and ethanol in aqueous solution are presented. For comparison, the 'H NMR spectrum of alanine in aqueous solution with the binomial ( I33 1,2662) spin-echo sequence is also shown. 0 1991 Academic press. IIIC.
Journal of magnetic resonance, 1988
A series of test experiments with the VOSY technique for volume-selective NMR spectroscopy has been carried out. A critical test of volume selection under chemical-shiftinduced offsets at 4.7 T is reported. It is demonstrated that several volume elements can LX probed in a single experiment so that metabolite concentrations can be related to other regions or to a calibration sample. The method can also be combined with spectral editing procedures such as the spin-echo double-resonance sequence (SEDQR). Q 1988 Academic Ress. Inc.
Multiple-pulse and magic-angle spinning aided double-quantum proton solid-state NMR spectroscopy
Chemical Physics Letters, 2004
We here report on a high-resolution pulse scheme for double-quantum (DQ) proton NMR spectroscopy in the solid-state. The pulse scheme employs a combination of multiple-pulses and magic-angle spinning (MAS) for both the excitation and conversion of DQ coherences and their evolution under homonuclear dipolar decoupling. This is made possible in this two-dimensional experiment by an effective combination of homonuclear dipolar decoupling method of phase modulated Lee-Goldburg and symmetry adapted sequence for homonuclear dipolar recoupling under MAS. DQ spectra of monoethyl fumaric acid, glycine, and histidine are presented to highlight the utility of the pulse scheme together with some of the existing drawbacks.
Singlet-filtered NMR spectroscopy
Science Advances
Selectively studying parts of proteins and metabolites in tissue with nuclear magnetic resonance promises new insights into molecular structures or diagnostic approaches. Nuclear spin singlet states allow the selection of signals from chemical moieties of interest in proteins or metabolites while suppressing background signal. This selection process is based on the electron-mediated coupling between two nuclear spins and their difference in resonance frequency. We introduce a generalized and versatile pulsed NMR experiment that allows populating singlet states on a broad scale of coupling patterns. This approach allowed us to filter signals from proton pairs in the Alzheimer’s disease–related b-amyloid 40 peptide and in metabolites in brain matter. In particular, for glutamine/glutamate, we have discovered a long-lived state in tissue without the typically required singlet sustaining by radiofrequency irradiation. We believe that these findings will open up new opportunities to stud...
Journal of Magnetic Resonance, 2003
The dependence of the (Rotor Assisted Population Transfer) RAPT enhancement on offset frequency for nuclei experiencing different quadrupolar couplings has been exploited to design two new spectral editing schemes, p=2-RAPT and RAPT-p-RAPT, for the selective excitation or suppression, respectively, of nuclei with large quadrupolar couplings. Both approaches are demonstrated on the 87 Rb spectrum of Rb 2 SO 4 , which contains two resonances with C q values of 2.6 and 5.3 MHz. The conditions for optimal selectivity are discussed. Combining p=2-RAPT with the RIACT MQ-MAS experiment it is also demonstrated how a pure absorption mode triple quantum MQ-MAS spectrum devoid of narrow resonances can be obtained.
ChemInform, 2010
| One of the significant advancements in Nuclear Magnetic Resonance spectroscopy (NMR) in combating the problem of spectral complexity for deriving the structure and conformational information is the incorporation of additional dimension and to spread the information content in a two dimensional space. This approach together with the manipulation of the dynamics of nuclear spins permitted the designing of appropriate pulse sequences leading to the evolution of diverse multidimensional NMR experiments. The desired spectral information can now be extracted in a simplified and an orchestrated manner. The indirect detection of multiple quantum (MQ) NMR frequencies is a step in this direction. The MQ technique has been extensively used in the study of molecules aligned in liquid crystalline media to reduce spectral complexity and to determine molecular geometries. Unlike in dipolar coupled systems, the size of the network of scalar coupled spins is not big in isotropic solutions and the MQ 1 H detection is not routinely employed, although there are specific examples of spin topology filtering. In this brief review, we discuss our recent studies on the development and application of multiple quantum correlation and resolved techniques for the analyses of proton NMR spectra of scalar coupled spins.
Fast multidimensional NMR spectroscopy by spin-state selective off-resonance decoupling (SITAR
Magnetic Resonance in Chemistry, 2006
Spin-state selective off-resonance decoupling (SITAR) is applied to the amide proton-to-nitrogen-toalpha-carbon correlation (HNCA) triple-resonance experiment by measuring the 15 N chemical shift during the acquisition simultaneously with the 1 H chemical shift. The simultaneous detection of both 1 H and 15 N chemical shifts in SITAR reduces the dimensionality of the HNCA-type experiment from three dimensions to two dimensions with a 15 N chemical shift resolution of ∼0.4 ppm. This enables the recording of triple-resonance experiments in several minutes. SITAR is furthermore applied to the amide proton-to-nitrogen-to-alpha-carbon-and-beta-carbon correlation (HNCACB) triple-resonance experiment and the 15 N-resolved [ 1 H, 1 H]-nuclear Overhauser enhancement spectroscopy (NOESY) experiment with similar success.
Theoretical treatment of volume-selective NMR spectroscop (VOSY) applied to coupled spin systems
Journal of magnetic resonance, 1989
With uncoupled spins, localized spectroscopy is possible by the aid of three slice-selective 90' RF pulses producing a volume-selective stimulated echo. Scalar spin-spin coupling, on the other hand, severely affects the coherence pathways excited by multipulse sequences. Using a product operator formalism we have calculated the signal expected for a J-coupled two-spin (l/2) system in dependence on the flip angles and pulse delays. The evolution of nquantum coherences and the conversion of coherences to longitudinal scalar order apart from regular longitudinal magnetization is described. All three types of intermediate spin states can be used to generate volume-selective signals by applying the sequence (?r/2)X-~1-(/3)y-~2-(6),,-r,-AQ consisting of three slice-selective RF pulses. Signals produced by conversion from longitudinal scalar order are, e.g., opti-mizedforB=6=z/4andT1=(2J)-'. O1989AcademicPress.Inc.
Magnetic Resonance in Medicine, 2005
The classical double-quantum editing sequence 90",-~-180",-~-90",-t,-90",-~-180",-~-AQ (T = 1/45) was rendered volume selective, by making slice selective the first 90" pulse and the two 180" pulses. Using simple rules to ensure optimum radio frequency phase coherence, this single-voxel editing sequence, reminiscent of a basic PRESS localization technique, was implemented on a whole-body 3 T spectrometer, and in vitro editing of lactate methyl protons was demonstrated without any significant loss in intrinsic sensitivity. The effectiveness of the proposed approach in vivo was also illustrated through the localized monitoring of lactate in the human leg during and after exercise.