The Experts below are selected from a list of 294 Experts worldwide ranked by ideXlab platform

Uwe Klose - One of the best experts on this subject based on the ideXlab platform.

  • Proton CSI without Solvent Suppression with strongly reduced field gradient related sideband artifacts
    Magnetic Resonance Materials in Physics Biology and Medicine, 2013
    Co-Authors: Grzegorz L. Chadzynski, Uwe Klose
    Abstract:

    Object Non-water-suppressed MRSI (magnetic resonance spectroscopy imaging) offers a number of advantages; however, spectra are hampered by the sideband artifacts. The origin of those is associated with the vibration of the gradient coils, and most of the sidebands are assumed to be related to the crusher gradients. The aim was to examine the dependency between the physical direction of the crushers and the sidebands. Additionally, the possibilities of optimization of the point resolved spectroscopy sequence (PRESS) were investigated. Materials and methods For the assessment of the sidebands, spectra at short echo time (TE) were collected at 3 T from standard water phantom. A homemade agar phantom was used to test the optimal strength of the crusher gradients. Optimized PRESS sequence was tested in vivo. Results The greatest sidebands were found to be associated with the crusher gradient in x -direction. Agar phantom and in vivo measurements revealed that reduction of the crusher’s strength to 5 mT/m could provide a significant minimization of the sidebands without raising the unwanted signals produced by volume selection. Conclusion This study demonstrates that crusher gradients in different directions produce a unique pattern of the sidebands. Moreover, optimization of the strength of crushers has been found to decrease sidebands so, the remaining part could be reduced in postprocessing.

  • proton csi without Solvent Suppression with strongly reduced field gradient related sideband artifacts
    Magnetic Resonance Materials in Physics Biology and Medicine, 2013
    Co-Authors: Grzegorz L. Chadzynski, Uwe Klose
    Abstract:

    Object Non-water-suppressed MRSI (magnetic resonance spectroscopy imaging) offers a number of advantages; however, spectra are hampered by the sideband artifacts. The origin of those is associated with the vibration of the gradient coils, and most of the sidebands are assumed to be related to the crusher gradients. The aim was to examine the dependency between the physical direction of the crushers and the sidebands. Additionally, the possibilities of optimization of the point resolved spectroscopy sequence (PRESS) were investigated.

William S. Price - One of the best experts on this subject based on the ideXlab platform.

  • Applications of WaterControl to TOCSY and COSY experiments
    Journal of Biomolecular NMR, 2020
    Co-Authors: Johnny Chen, Gang Zheng, Allan M. Torres, William S. Price
    Abstract:

    WaterControl is a Solvent Suppression method based on WATERGATE and PGSTE and is very efficient in selectively reducing the Solvent signal in 1D pulse-acquire and 2D NOESY of protein solutions. In this study, the WaterControl technique was appended to two common 2D NMR methods used in resonance assignment of proteins, namely TOCSY and CLIP-COSY. Similar to that observed in regular 1D pulse-acquire and 2D NOESY, the incorporation of WaterControl in these 2D methods led to excellent Solvent Suppression superior to that obtained using W3- or W5-based WATERGATE sequences. The water signal was essentially eliminated in the TOCSY and CLIP-COSY with WaterControl while useful cross peaks around the water resonance at ω_2 were preserved. This is in contrast to the 2D spectra obtained from the corresponding WATERGATE containing sequences, where these cross peaks in the ω_2 region are usually suppressed together with the water resonance. These new WaterControl sequences provide significantly improved water Suppression thereby facilitating protein NMR studies.

  • Chapter 2:Fundamentals of Diffusion Measurements using NMR
    New Developments in NMR, 2016
    Co-Authors: Scott A. Willis, Timothy Stait-gardner, Allan M. Torres, William S. Price
    Abstract:

    Nuclear magnetic resonance pulsed gradient-spin echo experiments allow probing complex solution properties of molecules that translational motion depends on. This introductory review covers aspects from the mathematical basics of diffusive motion to the averaging effects of obstruction and binding. An outline of some of the experimental aspects of diffusion measurements is also provided including data acquisition, fitting and Solvent Suppression.

  • Simultaneous convection compensation and Solvent Suppression in biomolecular NMR diffusion experiments.
    Journal of biomolecular NMR, 2009
    Co-Authors: Gang Zheng, William S. Price
    Abstract:

    Thermal convection and high intensity Solvent resonances can significantly hamper diffusion estimates in pulsed gradient spin-echo nuclear magnetic resonance diffusion experiments on biomolecule samples. To overcome these two problems, a new double functional NMR diffusion sequence, double echo PGSTE-WATERGATE, is presented. The new sequence provides excellent convection compensation and Solvent Suppression (with a Suppression factor in excess of at least 105 in a single scan) in biomolecular NMR diffusion experiments. Due to its stimulated echo nature, the new sequence is much less susceptible to spin–spin relaxation than Hahn spin-echo based sequences. Furthermore, the new sequence is not susceptible to spin diffusion due to the application of bipolar pulsed gradients. The new sequence is also much easier to set up compared to previously developed stimulated echo based convection compensation and Solvent Suppression sequence. The utility of the new sequence is demonstrated on an aqueous lysozyme sample.

  • Solvent Suppression using phase-modulated binomial-like sequences and applications to diffusion measurements
    Journal of magnetic resonance (San Diego Calif. : 1997), 2008
    Co-Authors: Gang Zheng, Allan M. Torres, William S. Price
    Abstract:

    Abstract Two phase-modulated binomial-like π pulses have been developed by simultaneously optimizing pulse durations and phases. In combination with excitation sculpting, both of the new binomial-like sequences outperform the well-known 3-9-19 sequence in selectivity and inversion width. The new sequences provide similar selectivity and inversion width to the W5 sequence but with significantly shorter sequence durations. When used in PGSTE-WATERGATE, they afford highly selective Solvent Suppression in diffusion experiments.

  • PGSTE-WATERGATE: an STE-based PGSE NMR sequence with excellent Solvent Suppression.
    Journal of magnetic resonance (San Diego Calif. : 1997), 2007
    Co-Authors: Gang Zheng, Timothy Stait-gardner, P. G. Anil Kumar, Allan M. Torres, William S. Price
    Abstract:

    Abstract A new stimulated-echo based pulsed gradient spin-echo NMR diffusion sequence incorporating WATERGATE Solvent Suppression, PGSTE-WATERGATE, is presented. The sequence provides superb Solvent Suppression without any phase distortions. The sequence is simple to set up and particularly suited to measuring diffusion coefficients in aqueous solution such as is commonly required in pharmaceutical and combinatorial applications. The utility of the sequence is demonstrated on samples containing lysozyme and sucrose. Importantly, the high degree of phase-distortion Suppression allows more complicated selective π pulses to be used to enhance the selectivity of Solvent Suppression.

Grzegorz L. Chadzynski - One of the best experts on this subject based on the ideXlab platform.

  • Proton CSI without Solvent Suppression with strongly reduced field gradient related sideband artifacts
    Magnetic Resonance Materials in Physics Biology and Medicine, 2013
    Co-Authors: Grzegorz L. Chadzynski, Uwe Klose
    Abstract:

    Object Non-water-suppressed MRSI (magnetic resonance spectroscopy imaging) offers a number of advantages; however, spectra are hampered by the sideband artifacts. The origin of those is associated with the vibration of the gradient coils, and most of the sidebands are assumed to be related to the crusher gradients. The aim was to examine the dependency between the physical direction of the crushers and the sidebands. Additionally, the possibilities of optimization of the point resolved spectroscopy sequence (PRESS) were investigated. Materials and methods For the assessment of the sidebands, spectra at short echo time (TE) were collected at 3 T from standard water phantom. A homemade agar phantom was used to test the optimal strength of the crusher gradients. Optimized PRESS sequence was tested in vivo. Results The greatest sidebands were found to be associated with the crusher gradient in x -direction. Agar phantom and in vivo measurements revealed that reduction of the crusher’s strength to 5 mT/m could provide a significant minimization of the sidebands without raising the unwanted signals produced by volume selection. Conclusion This study demonstrates that crusher gradients in different directions produce a unique pattern of the sidebands. Moreover, optimization of the strength of crushers has been found to decrease sidebands so, the remaining part could be reduced in postprocessing.

  • proton csi without Solvent Suppression with strongly reduced field gradient related sideband artifacts
    Magnetic Resonance Materials in Physics Biology and Medicine, 2013
    Co-Authors: Grzegorz L. Chadzynski, Uwe Klose
    Abstract:

    Object Non-water-suppressed MRSI (magnetic resonance spectroscopy imaging) offers a number of advantages; however, spectra are hampered by the sideband artifacts. The origin of those is associated with the vibration of the gradient coils, and most of the sidebands are assumed to be related to the crusher gradients. The aim was to examine the dependency between the physical direction of the crushers and the sidebands. Additionally, the possibilities of optimization of the point resolved spectroscopy sequence (PRESS) were investigated.

Zhong Chen - One of the best experts on this subject based on the ideXlab platform.

  • Ultrafast 1H J-resolved spectroscopy via 2H distant dipolar field in magnetic fields with unknown spatial variations
    Chemical Physics Letters, 2013
    Co-Authors: Hao Chen, Zhiyong Zhang, Kaiyu Wang, Shuhui Cai, Zhong Chen
    Abstract:

    Abstract Spatially encoded ultrafast NMR accelerates the acquisition of 2D NMR spectra by orders of magnitude, but it is affected by field inhomogeneity. To circumvent this influence, various approaches have been proposed. Here we propose a new scheme to ultrafast achieve 2D J -resolved spectroscopy in inhomogeneous fields via the distant dipolar field of deuterium nuclei. Compared to the methods via homonuclear distant dipolar field, the trouble of selective excitation and Solvent Suppression when the peaks of Solvent and solute spins are close to each other in inhomogeneous fields will be avoided. Theoretical analyses and experimental results are presented for verification.

  • High-resolution intermolecular zero-quantum coherence spectroscopy under inhomogeneous fields with effective Solvent Suppression.
    Physical Chemistry Chemical Physics, 2007
    Co-Authors: Xi Chen, Zhong Chen, Jianhui Zhong
    Abstract:

    Intermolecular zero-quantum coherences (iZQCs) are not susceptible to magnetic field inhomogeneities significantly larger than the dipolar correlation distance and can be used to obtain 1D high-resolution spectra in an inhomogeneous field. However, with the iZQC methods proposed previously, residual conventional single-quantum coherences (SQCs) originating mainly from Solvent resonance result in strong t1 ridge noises. A modified HOMOGENIZED with an intermolecular double-quantum filter (iDQF), named iDQF-HOMOGENIZED, is presented in this work to suppress the residual conventional SQC signals as well as Solvent iZQC signals. The Solvent-Suppression efficiency of the iDQF-HOMOGENIZED is analyzed and a thorough comparison of the new sequence with several relevant pulse sequences is made. Dramatic resolution enhancement and Solvent Suppression in the measurements of a piece of grape sarcocarp suggest potential applications of the method in in vivo spectroscopy.

  • A New Method for High‐Resolution NMR Spectra in Inhomogeneous Fields with Efficient Solvent Suppression
    Chinese Journal of Chemistry, 2007
    Co-Authors: Meijin Lin, Xi Chen, Zhi-wei Chen, Zhong Chen
    Abstract:

    High-resolution nuclear magnetic resonance (NMR) is one of the most powerful tools for analyzing molecular structures and dynamics. Magnetic field homogeneity is required for conventional high-resolution spectra. However, there are many chemical and/or biological circumstances where the spatial homogeneities of the magnetic fields are degraded. Intense Solvent signal is another obstacle for obtaining high-resolution spectra, especially in in vivo and in situ NMR spectroscopy. In this paper, a new pulse sequence based on intermolecular multiple quantum coherence (iMQC) was reported. This sequence can effectively remove the effect of magnetic field inhomogeneity and suppress the Solvent signal. It can recover the spectral information such as chemical shifts, coupling constants, multiplet patterns, and relative peak areas in inhomogeneous fields. Theoretical analyses and experimental verifications are presented to demonstrate the feasibility of this method.

  • a new method for high resolution nmr spectra in inhomogeneous fields with efficient Solvent Suppression
    Chinese Journal of Chemistry, 2007
    Co-Authors: Meijin Lin, Xi Chen, Zhi-wei Chen, Zhong Chen
    Abstract:

    High-resolution nuclear magnetic resonance (NMR) is one of the most powerful tools for analyzing molecular structures and dynamics. Magnetic field homogeneity is required for conventional high-resolution spectra. However, there are many chemical and/or biological circumstances where the spatial homogeneities of the magnetic fields are degraded. Intense Solvent signal is another obstacle for obtaining high-resolution spectra, especially in in vivo and in situ NMR spectroscopy. In this paper, a new pulse sequence based on intermolecular multiple quantum coherence (iMQC) was reported. This sequence can effectively remove the effect of magnetic field inhomogeneity and suppress the Solvent signal. It can recover the spectral information such as chemical shifts, coupling constants, multiplet patterns, and relative peak areas in inhomogeneous fields. Theoretical analyses and experimental verifications are presented to demonstrate the feasibility of this method.

D. Bruce Fulton - One of the best experts on this subject based on the ideXlab platform.

  • Gradient-enhanced TOCSY experiments with improved sensitivity and Solvent Suppression.
    Journal of biomolecular NMR, 1996
    Co-Authors: D. Bruce Fulton, Richard Hrabal
    Abstract:

    Gradient-enhanced versions of the homonuclear TOCSY experiment are described, with Solvent Suppression and sensitivity superior to that of a conventional TOCSY experiment. The pulse sequences are constructed by appending a WATERGATE module to a z-filtered TOCSY experiment. Pulsed-field gradients and appropriately phased selective rf pulses are used to maintain precise control of the water magnetization vector. Problems associated with radiation damping and spin-locking of the water magnetization are thus alleviated. The water magnetization is returned to equilibrium prior to each acquisition, which improves water Suppression and minimizes signal losses due to saturation transfer.

  • Detection and determination of dilute, low molecular weight organic compounds in water by 500-MHz proton nuclear magnetic resonance spectroscopy
    Analytical Chemistry, 1992
    Co-Authors: D. Bruce Fulton, Brian G. Sayer, Alex D. Bain, Harold V. Malle
    Abstract:

    The feasibility of using high-field proton NMR spectroscopy to analyze aqueous solutions of organic solutes at micromolar concentrations has been evaluated. N-Nitrosodimethylamine (NDMA) and benzene served as model compounds. The WATR (water attenuation by transverse relaxation) method of Solvent Suppression was optimized to permit detection of the protons of analytes in the submicromolar concentration regime. All data were collected in blocks to permit quantitative estimation of detection limits and experimental error