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Hartmut Oschkinat - One of the best experts on this subject based on the ideXlab platform.
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1h detection in mas solid state nmr spectroscopy of biomacromolecules employing Pulsed Field Gradients for residual solvent suppression
Journal of the American Chemical Society, 2003Co-Authors: Veniamin Chevelkov, Hartmut Oschkinat, Barth Van Rossum, Federica Castellani, Kristina Rehbein, Anne Diehl, M Hohwy, Stefan Steuernagel, Frank Engelke, Bernd ReifAbstract:In this communication, we demonstrate the feasibility of 1H detection in MAS solid-state NMR for a microcrystalline, uniformly 2H,15N-labeled sample of a SH3 domain of chicken alpha-spectrin, using Pulsed Field Gradients for suppression of water magnetization. Today, B0 Gradients are employed routinely in solution-state NMR for coherence order selection and solvent suppression. We suggest to use Gradients to purge water magnetization which cannot be suppressed using conventional water suppression schemes. The achievable gain in sensitivity for 1H detection is in the order of 5 compared to the 15N detected version of the experiment (at a MAS rotation frequency of 13.5 kHz). We expect that this labeling concept which achieves high sensitivity due to 1H detection, in combination with the possibility to measure long range 1H-1H distances as we have shown previously, to be a useful tool for the determination of protein structures in the solid state.
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signal selection in high resolution nmr by Pulsed Field Gradients ii the design of gradient pulse sequences
Journal of Magnetic Resonance, 1999Co-Authors: David J Thomas, Lorenz Mitschang, Bernd Simon, Hartmut OschkinatAbstract:We describe a new and powerful computer program called TRIPLE GRADIENT which calculates optimized Pulsed Field gradient sequences for specific coherence pathway selection or rejection. Sequences can be computed for gradient coils acting along one, two, or three perpendicular axes. The program is based on the computational minimization of a penalty function formed from the summed amplitudes of the unwanted signals. The underlying mathematical analysis makes use of a vectorial representation of the way in which a gradient sequence suppresses different signals. It is argued that experiments using well-calculated gradient sequences are quicker and generally perform better than those using extensive phase cycling, especially when suppressing extremely strong solvent signals, and it is shown that in many cases gradient experiments of optimal signal-to-noise ratio can be performed. These claims are illustrated by spectra obtained from an HQQC experiment.
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regular articlesignal selection in high resolution nmr by Pulsed Field Gradients ii the design of gradient pulse sequences
Journal of Magnetic Resonance, 1999Co-Authors: David J Thomas, Lorenz Mitschang, Bernd Simon, Hartmut OschkinatAbstract:We describe a new and powerful computer program called TRIPLE GRADIENT which calculates optimized Pulsed Field gradient sequences for specific coherence pathway selection or rejection. Sequences can be computed for gradient coils acting along one, two, or three perpendicular axes. The program is based on the computational minimization of a penalty function formed from the summed amplitudes of the unwanted signals. The underlying mathematical analysis makes use of a vectorial representation of the way in which a gradient sequence suppresses different signals. It is argued that experiments using well-calculated gradient sequences are quicker and generally perform better than those using extensive phase cycling, especially when suppressing extremely strong solvent signals, and it is shown that in many cases gradient experiments of optimal signal-to-noise ratio can be performed. These claims are illustrated by spectra obtained from an HQQC experiment.
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Geometrical representation of coherence transfer selection by Pulsed Field Gradients in high‐resolution nuclear magnetic resonance
Journal of Chemical Physics, 1995Co-Authors: Lorenz Mitschang, Hannes Ponstingl, David Grindrod, Hartmut OschkinatAbstract:A formalism for the calculation of suitable sequences of Pulsed Field Gradients for signal selection in high‐resolution NMR spectroscopy is presented. It is based on a geometrical interpretation of coherence transfer pathway selection by Pulsed Field Gradients. The formalism allows the calculation of the suppression rates for undesired pathways and the determination of the most efficient sequence of Pulsed Field Gradients. As an example, sequences for multiplicity filtered 13C/1H correlation experiments are calculated and analyzed.
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geometrical representation of coherence transfer selection by Pulsed Field Gradients in high resolution nuclear magnetic resonance
Journal of Chemical Physics, 1995Co-Authors: Lorenz Mitschang, Hannes Ponstingl, David Grindrod, Hartmut OschkinatAbstract:A formalism for the calculation of suitable sequences of Pulsed Field Gradients for signal selection in high‐resolution NMR spectroscopy is presented. It is based on a geometrical interpretation of coherence transfer pathway selection by Pulsed Field Gradients. The formalism allows the calculation of the suppression rates for undesired pathways and the determination of the most efficient sequence of Pulsed Field Gradients. As an example, sequences for multiplicity filtered 13C/1H correlation experiments are calculated and analyzed.
Petrik Galvosas - One of the best experts on this subject based on the ideXlab platform.
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In situ determination of surface relaxivities for unconsolidated sediments
Water Resources Research, 2015Co-Authors: Markus Duschl, Petrik Galvosas, Timothy I. Brox, Andreas Pohlmeier, Harry VereeckenAbstract:NMR relaxometry has developed into a method for rapid pore size determination of natural porous media. Nevertheless, it is prone to uncertainties because of unknown surface relaxivities which depend mainly on the chemical composition of the pore walls as well as on the interfacial dynamics of the pore fluid. The classical approach for the determination of surface relaxivities is the scaling of NMR relaxation times by surface to volume ratios measured by gas adsorption or mercury intrusion. However, it is preferable that a method for the determination of average pore sizes uses the same substance, water, as probe molecule for both relaxometry and surface to volume measurements. One should also ensure that in both experiments the dynamics of the probe molecule takes place on similar length scales, which are in the order of some microns. Therefore, we employed NMR diffusion measurements with different observation times using bipolar Pulsed Field Gradients and applied them to unconsolidated sediments (two purified sands, two natural sands, and one soil). The evaluation by Mitra's short time model for diffusion in restricted environments yielded information about the surface to volume ratios which is independent of relaxation mechanisms. We point out that methods based on NMR diffusometry yield pore dimensions and surface relaxivities consistent with a pore space as sampled by native pore fluids via the diffusion process. This opens a way to calibrate NMR relaxation measurements with other NMR techniques, providing information about the pore size distribution of natural porous media directly from relaxometry. This article is protected by copyright. All rights reserved.
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Investigation of Molecular Exchange Using DEXSY with Ultra‐High Pulsed Field Gradients
AIP Conference Proceedings, 2008Co-Authors: Marcel Gratz, Petrik GalvosasAbstract:Diffusion exchange spectroscopy has been employed for the investigation of water exchange between different regions of a cosmetic lotion as well as for the exchange of n‐pentane between the inter‐ and intra‐crystalline space in zeolite NaX. We successfully combined this two‐dimensional (2D) NMR experiment with methods for the application of ultra‐high Pulsed Field Gradients of up to 35 T/m, resulting in observation times and mixing times as short as 2 ms and 2.8 ms, respectively.
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investigation of molecular exchange using dexsy with ultra high Pulsed Field Gradients
MAGNETIC RESONANCE IN POROUS MEDIA: Proceedings of the 9th International Bologna#N#Conference on Magnetic Resonance in Porous Media (MRPM9) including , 2008Co-Authors: Marcel Gratz, Petrik GalvosasAbstract:Diffusion exchange spectroscopy has been employed for the investigation of water exchange between different regions of a cosmetic lotion as well as for the exchange of n‐pentane between the inter‐ and intra‐crystalline space in zeolite NaX. We successfully combined this two‐dimensional (2D) NMR experiment with methods for the application of ultra‐high Pulsed Field Gradients of up to 35 T/m, resulting in observation times and mixing times as short as 2 ms and 2.8 ms, respectively.
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Background gradient suppression in stimulated echo NMR diffusion studies using magic Pulsed Field gradient ratios.
Journal of Magnetic Resonance, 2004Co-Authors: Petrik Galvosas, Frank Stallmach, Jörg KärgerAbstract:Abstract By evaluating the spin echo attenuation for a generalized 13-interval PFG NMR sequence consisting of Pulsed Field Gradients with four different effective intensities ( F p/r and G p/r ), magic Pulsed Field gradient (MPFG) ratios for the prepare ( G p / F p ) and the read ( G r / F r ) interval are derived, which suppress the cross term between background Field Gradients and the Pulsed Field Gradients even in the cases where the background Field Gradients may change during the z -store interval of the pulse sequence. These MPFG ratios depend only on the timing of the Pulsed Gradients in the pulse sequence and allow a convenient experimental approach to background gradient suppression in NMR diffusion studies with heterogeneous systems, where the local properties of the (internal) background Gradients are often unknown. If the Pulsed Field Gradients are centered in the τ -intervals between the π and π/2 rf pulses, these two MPFG ratios coincide to η = G p/r / F p/r =1−8/[1+(1/3)( δ / τ ) 2 ]. Since the width of the Pulsed Field Gradients ( δ ) is bounded by 0⩽ δ ⩽ τ , η can only be in the range of 5⩽− η ⩽7. The predicted suppression of the unwanted cross terms is demonstrated experimentally using time-dependent external Gradients which are controlled in the NMR experiment as well as spatially dependent internal background Gradients generated by the magnetic properties of the sample itself. The theoretical and experimental results confirm and extend the approach of Sun et al. (J. Magn. Reson. 161 (2003) 168), who recently introduced a 13-interval type PFG NMR sequence with two asymmetric Pulsed magnetic Field Gradients suitable to suppress unwanted cross terms with spatially dependent background Field Gradients.
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generation and application of ultra high intensity magnetic Field gradient pulses for nmr spectroscopy
Journal of Magnetic Resonance, 2001Co-Authors: Petrik Galvosas, Jörg Kärger, Frank Stallmach, Gunter Seiffert, Udo Kaess, G MajerAbstract:Abstract Two different concepts of gradient current power supplies are introduced, which are suitable for the generation of ultra-high intensity Pulsed magnetic Field Gradients of alternating polarity. The first system consists of a directly binary coded current source (DBCCS). It yields current pulses of up to ±120 A and a maximum voltage across the gradient coil of ±400 V. The second system consists of two TECHRON 8606 power supplies in push–pull configuration (PSPPC). It yields current pulses of up to ±100 A and a maximum voltage across the gradient coil of ±300 V. In combination with actively shielded anti-Helmholtz gradient coils, both systems are used routinely in NMR diffusion studies with unipolar Pulsed Field Gradients of up to 35 T/m. Until now, alternating Pulsed Field gradient experiments were successfully performed with gradient intensities of up to ±25 T/m (DBCCS) and ±35 T/m (PSPPC), respectively. Based on the observation of the NMR spin echo in the presence of a small read gradient, procedures to test the stability and the matching of such ultra-high Pulsed Field gradient intensities as well as an automated routine for the compensation of possible mismatches are introduced. The results of these procedures are reported for the PSPPC system.
Geoffrey Bodenhausen - One of the best experts on this subject based on the ideXlab platform.
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Speeding up nuclear magnetic resonance spectroscopy by the use of SMAll Recovery Times - SMART NMR.
Journal of Magnetic Resonance, 2010Co-Authors: Bruno Vitorge, Geoffrey Bodenhausen, Philippe PelupessyAbstract:A drastic reduction of the time required for two-dimensional NMR experiments can be achieved by reducing or skipping the recovery delay between successive experiments. Novel SMAll Recovery Times (SMART) methods use orthogonal Pulsed Field Gradients in three spatial directions to select the desired pathways and suppress interference effects. Two-dimensional spectra of dilute amino acids with concentrations as low as 2 mM can be recorded in about 0.1 s per increment in the indirect domain.
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Single or triple Gradients
Journal of Magnetic Resonance, 2008Co-Authors: Riddhiman Sarkar, Fabien Ferrage, Detlef Moskau, Paul R. Vasos, Geoffrey BodenhausenAbstract:Pulsed Field Gradients (PFGs) have become ubiquitous tools not only for Magnetic Resonance Imaging (MRI), but also for NMR experiments designed to study translational diffusion, for spatial encoding in ultra-fast spectroscopy, for the selection of desirable coherence transfer pathways, for the suppression of solvent signals, and for the elimination of zero-quantum coherences. Some of these experiments can only be carried out if three orthogonal Gradients are available, while others can also be implemented using a single gradient, albeit at some expense of performance. This paper discusses some of the advantages of triple- with respect to single-gradient probes. By way of examples we discuss (i) the measurement of small diffusion coefficients making use of the long spin-lattice relaxation times of nuclei with low gyromagnetic ratios γ such as nitrogen-15, and (ii) the elimination of zero-quantum coherences in Exchange or Nuclear Overhauser Spectroscopy (EXSY or NOESY) experiments, as well as in methods relying on long-lived (singlet) states to study very slow exchange or diffusion processes.
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Slow diffusion of macromolecular assemblies by a new Pulsed Field gradient NMR method
Journal of the American Chemical Society, 2003Co-Authors: Fabien Ferrage, Manuela Zoonens, Dror E. Warschawski, Jean-luc Popot, Geoffrey BodenhausenAbstract:The translational diffusion coefficient of an integral membrane protein/surfactant complex has been measured using a novel Pulsed Field gradient NMR method. In this new approach, the information about the localization of the molecules is temporarily stored in the form of longitudinal magnetization of isotopes with long spin−lattice relaxation times. This allows one to increase the duration of the diffusion interval by about 1 order of magnitude. Unlike standard proton NMR methods using Pulsed Field Gradients and stimulated echoes, the new method can be applied to macromolecular assemblies with diffusion coefficients well below 10-10 m2 s-1, corresponding to masses in excess of 25 kDa in aqueous solution at room temperature. The method was illustrated by application to a water-soluble complex of tOmpA, the hydrophobic transmembrane domain of bacterial outer membrane protein A, with the detergent octyl-tetraoxyethylene (C8E4; overall mass of complex ∼45 kDa). The diffusion coefficient was found to be D = (4...
Christian Griesinger - One of the best experts on this subject based on the ideXlab platform.
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heteronuclear multidimensional nmr experiments for the structure determination of proteins in solution employing Pulsed Field Gradients
Progress in Nuclear Magnetic Resonance Spectroscopy, 1999Co-Authors: Michael Sattler, Jurgen Schleucher, Christian GriesingerAbstract:Heteronuclear multidimensional NMR experiments for the structure determination of proteins in solution employing Pulsed Field Gradients
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novel pulse sequences with sensitivity enhancement for in phase coherence transfer employing Pulsed Field Gradients
Journal of Magnetic Resonance Series B, 1995Co-Authors: Michael Sattler, Jurgen Schleucher, P O Schmidt, O Schedletzky, Steffen J Glaser, Christian GriesingerAbstract:Novel pulse sequences for in-phase coherence order selective coherence transfer (ICOS-CT) S− → F− in an InS spin system employing heteronuclear gradient echos are introduced and evaluated in theory and experiment, It is shown that the heteronuclear isotropic mixing Hamiltonian Hiso = (2πJ/3)(FzSz + FxSx + FySy) or successive bilinear rotations along the x, y, and z axes achieve ICOS-CT, In the absence of homonuclear S couplings, the heteronuclear isotropic mixing performs best with respect to sensitivity for all multiplicities, In the presence of homonuclear S couplings, however, two pulse sequences based on successive bilinear rotations, yxz-ICOS-CT and xyz-ICOS-CT, represent the optimum, These sequences were tested experimentally on a 13C-labeled protein and an unlabeled peptide, The performance of the two sequences is comparable, with a slight advantage for the yxz-ICOS-CT sequence.
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novel strategies for sensitivity enhancement in heteronuclear multi dimensional nmr experiments employing Pulsed Field Gradients
Journal of Biomolecular NMR, 1995Co-Authors: Michael Sattler, Jurgen Schleucher, M G Schwendinger, Christian GriesingerAbstract:Novel strategies for sensitivity enhancement in heteronuclear multidimensional spectra are introduced and evaluated theoretically and experimentally. It is shown that in 3D sequences employing several Coherence Order Selective Coherence Transfer (COS-CT) steps, enhancement factors of up to 2 can be achieved. This sensitivity enhancement is compatible with the use of heteronuclear gradient echoes, yielding spectra with excellent water suppression. HNCO and HCCH-TOCSY pulse sequences are proposed and experimentally tested. These experiments employ recently developed coherence order selective pulse sequence elements, e.g., COS-INEPT and planar TOCSY for antiphase to in-phase transfers 2F-S2↔S- or in-phaseaCOS-CT for in-phase transfer F-↔S-, and the well-known isotropic TOCSY mixing sequences for homo- and heteronuclear in-phase transfer.
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a general enhancement scheme in heteronuclear multidimensional nmr employing Pulsed Field Gradients
Journal of Biomolecular NMR, 1994Co-Authors: Jurgen Schleucher, Ole W Sorensen, Michael Sattler, M G Schwendinger, P O Schmidt, O Schedletzky, Steffen J Glaser, Christian GriesingerAbstract:General pulse sequence elements that achieve sensitivity-enhanced coherence transfer from a heteronucleus to protons of arbitrary multiplicity are introduced. The building blocks are derived from the sensitivity-enhancement scheme introduced by Cavanagh et al. ((1991) J. Magn. Reson., 91, 429-436), which was used in conjunction with gradient coherence selection by Kay et al. ((1992) J. Am. Chem. Soc., 114, 10663-10665), as well as from a multiple-pulse sequence effecting a heteronuclear planar coupling Hamiltonian. The building blocks are incorporated into heteronuclear correlation experiments, in conjunction with coherence selection by the formation of a heteronuclear gradient echo. This allows for efficient water suppression without the need for water presaturation. The methods are demonstrated in HSQC-type experiments on a sample of a decapeptide in H2O. The novel pulse sequence elements can be incorporated into multidimensional experiments.
Lorenz Mitschang - One of the best experts on this subject based on the ideXlab platform.
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signal selection in high resolution nmr by Pulsed Field Gradients i geometrical analysis
Journal of Magnetic Resonance, 1999Co-Authors: Lorenz MitschangAbstract:A geometrical description for the selection of coherence transfer pathways in high resolution NMR by the application of Pulsed Field Gradients along three orthogonal directions in space is presented. The response of the spin system is one point of the three-dimensional Fourier transform of the sample volume affected by a sequence of Field Gradients. The property that a pathway is retained (or suppressed) when a sequence of Field Gradients is applied is expressed by the property of vectors, representing the pathway and the sequence, respectively, to be orthogonal (or not orthogonal). Ignoring imperfections of RF pulses, and with the exception of sensitivity enhanced experiments and experiments where the relevant coherence order is zero while Field Gradients are applied, it is shown that at most only half of the relevant pathways, as compared to a phase cycled experiment, are retained when Field Gradients are used for signal selection.
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signal selection in high resolution nmr by Pulsed Field Gradients ii the design of gradient pulse sequences
Journal of Magnetic Resonance, 1999Co-Authors: David J Thomas, Lorenz Mitschang, Bernd Simon, Hartmut OschkinatAbstract:We describe a new and powerful computer program called TRIPLE GRADIENT which calculates optimized Pulsed Field gradient sequences for specific coherence pathway selection or rejection. Sequences can be computed for gradient coils acting along one, two, or three perpendicular axes. The program is based on the computational minimization of a penalty function formed from the summed amplitudes of the unwanted signals. The underlying mathematical analysis makes use of a vectorial representation of the way in which a gradient sequence suppresses different signals. It is argued that experiments using well-calculated gradient sequences are quicker and generally perform better than those using extensive phase cycling, especially when suppressing extremely strong solvent signals, and it is shown that in many cases gradient experiments of optimal signal-to-noise ratio can be performed. These claims are illustrated by spectra obtained from an HQQC experiment.
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regular articlesignal selection in high resolution nmr by Pulsed Field Gradients ii the design of gradient pulse sequences
Journal of Magnetic Resonance, 1999Co-Authors: David J Thomas, Lorenz Mitschang, Bernd Simon, Hartmut OschkinatAbstract:We describe a new and powerful computer program called TRIPLE GRADIENT which calculates optimized Pulsed Field gradient sequences for specific coherence pathway selection or rejection. Sequences can be computed for gradient coils acting along one, two, or three perpendicular axes. The program is based on the computational minimization of a penalty function formed from the summed amplitudes of the unwanted signals. The underlying mathematical analysis makes use of a vectorial representation of the way in which a gradient sequence suppresses different signals. It is argued that experiments using well-calculated gradient sequences are quicker and generally perform better than those using extensive phase cycling, especially when suppressing extremely strong solvent signals, and it is shown that in many cases gradient experiments of optimal signal-to-noise ratio can be performed. These claims are illustrated by spectra obtained from an HQQC experiment.
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Geometrical representation of coherence transfer selection by Pulsed Field Gradients in high‐resolution nuclear magnetic resonance
Journal of Chemical Physics, 1995Co-Authors: Lorenz Mitschang, Hannes Ponstingl, David Grindrod, Hartmut OschkinatAbstract:A formalism for the calculation of suitable sequences of Pulsed Field Gradients for signal selection in high‐resolution NMR spectroscopy is presented. It is based on a geometrical interpretation of coherence transfer pathway selection by Pulsed Field Gradients. The formalism allows the calculation of the suppression rates for undesired pathways and the determination of the most efficient sequence of Pulsed Field Gradients. As an example, sequences for multiplicity filtered 13C/1H correlation experiments are calculated and analyzed.
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geometrical representation of coherence transfer selection by Pulsed Field Gradients in high resolution nuclear magnetic resonance
Journal of Chemical Physics, 1995Co-Authors: Lorenz Mitschang, Hannes Ponstingl, David Grindrod, Hartmut OschkinatAbstract:A formalism for the calculation of suitable sequences of Pulsed Field Gradients for signal selection in high‐resolution NMR spectroscopy is presented. It is based on a geometrical interpretation of coherence transfer pathway selection by Pulsed Field Gradients. The formalism allows the calculation of the suppression rates for undesired pathways and the determination of the most efficient sequence of Pulsed Field Gradients. As an example, sequences for multiplicity filtered 13C/1H correlation experiments are calculated and analyzed.
