Localized double-quantum-filtered 1 H NMR spectroscopy (original) (raw)
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Double-quantum filtered volume-selective NMR spectroscopy
Magnetic Resonance in Medicine, 1989
RF and field-gradient pulse sequence is presented, permitting the recording of localized double-quantum filtered proton spectra. In this way distinction between overlapping resonances of coupled and uncoupled spins is possible. The editing of the lactate methyl line is demonstrated in a test experiment.
Metabolite‐specific NMR spectroscopy in vivo
NMR in Biomedicine, 1997
An outline is presented of metabolite-specific in vivo NMR spectroscopy (particularly in brain). It reviews from a physical spectroscopist's perspective, the need for and the methods of observation of, individual metabolite resonances. © Abbreviations used: AX, Two single spins weakly coupled; AB, Two single spins strongly coupled; AX 3 , A single spin weakly coupled to a group of three spins; A 2 M 2 X 2 , Three weakly coupled spin pairs; AMNPQ, A single spin weakly coupled to two internally strongly coupled pairs of spins, the coupling between which is also strong; B 0 , Static magnetic field . A limited region (2 ppm to 3 ppm) of the 300 MHz proton spectrum from an acid extract of cat brain, reproduced by kind permission of Dr C. C. Hanstock.
High-Resolution Two-Dimensional J-Resolved NMR Spectroscopy for Biological Systems
Biophysical Journal, 2014
NMR spectroscopy is a principal tool in metabolomic studies and can, in theory, yield atom-level information critical for understanding biological systems. Nevertheless, NMR investigations on biological tissues generally have to contend with field inhomogeneities originating from variations in macroscopic magnetic susceptibility; these field inhomogeneities broaden spectral lines and thereby obscure metabolite signals. The congestion in one-dimensional NMR spectra of biological tissues often leads to ambiguities in metabolite identification and quantification. We propose an NMR approach based on intermolecular double-quantum coherences to recover high-resolution two-dimensional (2D) J-resolved spectra from inhomogeneous magnetic fields, such as those created by susceptibility variations in intact biological tissues. The proposed method makes it possible to acquire high-resolution 2D J-resolved spectra on intact biological samples without recourse to time-consuming shimming procedures or the use of specialized hardware, such as magic-angle-spinning probes. Separation of chemical shifts and J couplings along two distinct dimensions is achieved, which reduces spectral crowding and increases metabolite specificity. Moreover, the apparent J coupling constants observed are magnified by a factor of 3, facilitating the accurate measurement of small J couplings, which is useful in metabolic analyses. Dramatically improved spectral resolution is demonstrated in our applications of the technique on pig brain tissues. The resulting spectra contain a wealth of chemical shift and J-coupling information that is invaluable for metabolite analyses. A spatially localized experiment applied on an intact fish (Crossocheilus siamensis) reveals the promise of the proposed method in in vivo metabolite studies. Moreover, the proposed method makes few demands on spectrometer hardware and therefore constitutes a convenient and effective manner for metabonomics study of biological systems.
Application of multipulse NMR to observe ¹³C-labeled metabolites in biological systems
Magnetic Resonance in Medicine, 1985
Limitations in resolution and sensitivity of I3C NMR spectroscopy have reduced the information obtainable from intact biological systems. With the aim of increasing the information from in vivo "C NMR two multipulse NMR techniques, the DEPT pulse sequence and the gated spin-echo sequence, were used to obtain edited I3C NMR spectra from different 13C-labeled mammalian tissues. This allowed the separation of the "C NMR signals from the tissues into subspectra containing either CH, CH2, or CH3 signals, thereby increasing the information obtainable from these spectra. Comparing the two techniques, the DEPT sequence gives more accurate editing than the gated spin-echo sequence but suffers from the difficulty of determining 'H pulse angles in vivo.
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...
Nmr in Biomedicine, 2006
High-resolution magic angle spinning (HR-MAS) 1H NMR spectroscopy of intact human liver needle biopsies has not been previously reported. HR-MAS NMR spectra collected on 17 specimens with tissue amounts between ∼0.5 and 12 mg showed very good spectral resolution and signal-to-noise ratios. One-dimensional 1H spectra revealed many intense signals corresponding to cellular metabolites. In addition, some high molecular weight metabolites, such as glycogen and mobile fatty acids, could be observed in some spectra. Resonance assignments for 22 metabolites were obtained by combining the analysis of three different types of 1D 1H spectral editing, such as T2 filtering or the nuclear Overhauser effect and 2D TOCSY and 13C-HSQC spectra. Biochemical stability of the liver tissue during up to 16 h of magic angle spinning at 277 K was studied. Biochemical trends corresponding to the different pathologies were observed, involving free fragments of lipids among other metabolites. NMR signal intensity ratios can be useful for discrimination among non-pathological, hepatitis C affected and cirrhotic liver tissues. Overall, this work demonstrates the applicability of HR-MAS NMR spectroscopy to the biochemical characterization of needle biopsies of the human liver. Copyright © 2006 John Wiley & Sons, Ltd.
Robust Metabolite Quantification from J-Compensated 2D 1H-13C-HSQC Experiments
Metabolites
The spectral resolution of 2D 1H-13C heteronuclear single quantum coherence (1H-13C-HSQC) nuclear magnetic resonance (NMR) spectra facilitates both metabolite identification and quantification in nuclear magnetic resonance-based metabolomics. However, quantification is complicated by variations in magnetization transfer, which among others originate mainly from scalar coupling differences. Methods that compensate for variation in scalar coupling include the generation of calibration factors for individual signals or the use of additional pulse sequence schemes such as quantitative HSQC (Q-HSQC) that suppress the JCH-dependence by modulating the polarization transfer delays of HSQC or, additionally, employ a pure-shift homodecoupling approach in the 1H dimension, such as Quantitative, Perfected and Pure Shifted HSQC (QUIPU-HSQC). To test the quantitative accuracy of these three methods, employing a 600 MHz NMR spectrometer equipped with a helium cooled cryoprobe, a Latin-square desig...
Applications of NMR spectroscopy to systems biochemistry
Progress in nuclear magnetic resonance spectroscopy, 2016
The past decades of advancements in NMR have made it a very powerful tool for metabolic research. Despite its limitations in sensitivity relative to mass spectrometric techniques, NMR has a number of unparalleled advantages for metabolic studies, most notably the rigor and versatility in structure elucidation, isotope-filtered selection of molecules, and analysis of positional isotopomer distributions in complex mixtures afforded by multinuclear and multidimensional experiments. In addition, NMR has the capacity for spatially selective in vivo imaging and dynamical analysis of metabolism in tissues of living organisms. In conjunction with the use of stable isotope tracers, NMR is a method of choice for exploring the dynamics and compartmentation of metabolic pathways and networks, for which our current understanding is grossly insufficient. In this review, we describe how various direct and isotope-edited 1D and 2D NMR methods can be employed to profile metabolites and their isotopo...