The Experts below are selected from a list of 126 Experts worldwide ranked by ideXlab platform

Eduard Y. Chekmenev - One of the best experts on this subject based on the ideXlab platform.

  • Generalizing, Extending, and Maximizing Nitrogen-15 Hyperpolarization Induced by Parahydrogen in Reversible Exchange
    The journal of physical chemistry. C Nanomaterials and interfaces, 2017
    Co-Authors: Johannes F. P. Colell, Angus W. J. Logan, Zijian Zhou, Roman V. Shchepin, Danila A. Barskiy, Gerardo X. Ortiz, Qiu Wang, Steven J. Malcolmson, Eduard Y. Chekmenev, Warren S. Warren
    Abstract:

    Signal Amplification by Reversible Exchange (SABRE) is a fast and convenient NMR hyperpolarization method that uses cheap and readily available para-hydrogen as a hyperpolarization source. SABRE can hyperpolarize protons and heteronuclei. Here we focus on the heteronuclear variant introduced as SABRE-SHEATH (SABRE in SHield Enables Alignment Transfer to Heteronuclei) and Nitrogen-15 targets in particular. We show that 15N-SABRE works more efficiently and on a wider range of substrates than 1H-SABRE, greatly generalizing the SABRE approach. In addition, we show that Nitrogen-15 offers significantly extended T1 times of up to 12 minutes. Long T1 times enable higher hyperpolarization levels but also hold the promise of hyperpolarized molecular imaging for several tens of minutes. Detailed characterization and optimization are presented, leading to Nitrogen-15 polarization levels in excess of 10% on several compounds.

  • Microtesla SABRE Enables 10% Nitrogen-15 Nuclear Spin Polarization
    Journal of the American Chemical Society, 2015
    Co-Authors: Thomas Theis, Roman V. Shchepin, Warren S. Warren, Milton L. Truong, Aaron M. Coffey, Kevin W. Waddell, Fan Shi, Boyd M. Goodson, Eduard Y. Chekmenev
    Abstract:

    Parahydrogen is demonstrated to efficiently transfer its nuclear spin hyperpolarization to Nitrogen-15 in pyridine and nicotinamide (vitamin B3 amide) by conducting “signal amplification by reversible exchange” (SABRE) at microtesla fields within a magnetic shield. Following transfer of the sample from the magnetic shield chamber to a conventional NMR spectrometer, the 15N NMR signals for these molecules are enhanced by ∼30,000- and ∼20,000-fold at 9.4 T, corresponding to ∼10% and ∼7% nuclear spin polarization, respectively. This method, dubbed “SABRE in shield enables alignment transfer to heteronuclei” or “SABRE-SHEATH”, promises to be a simple, cost-effective way to hyperpolarize heteronuclei. It may be particularly useful for in vivo applications because of longer hyperpolarization lifetimes, lack of background signal, and facile chemical-shift discrimination of different species.

  • microtesla sabre enables 10 Nitrogen 15 nuclear spin polarization
    Journal of the American Chemical Society, 2015
    Co-Authors: Thomas Theis, Roman V. Shchepin, Warren S. Warren, Milton L. Truong, Aaron M. Coffey, Kevin W. Waddell, Fan Shi, Boyd M. Goodson, Eduard Y. Chekmenev
    Abstract:

    Parahydrogen is demonstrated to efficiently transfer its nuclear spin hyperpolarization to Nitrogen-15 in pyridine and nicotinamide (vitamin B3 amide) by conducting “signal amplification by reversible exchange” (SABRE) at microtesla fields within a magnetic shield. Following transfer of the sample from the magnetic shield chamber to a conventional NMR spectrometer, the 15N NMR signals for these molecules are enhanced by ∼30,000- and ∼20,000-fold at 9.4 T, corresponding to ∼10% and ∼7% nuclear spin polarization, respectively. This method, dubbed “SABRE in shield enables alignment transfer to heteronuclei” or “SABRE-SHEATH”, promises to be a simple, cost-effective way to hyperpolarize heteronuclei. It may be particularly useful for in vivo applications because of longer hyperpolarization lifetimes, lack of background signal, and facile chemical-shift discrimination of different species.

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

  • The influence of Nitrogen-15 proton-driven spin diffusion on the measurement of Nitrogen-15 longitudinal relaxation times.
    J Magn Reson, 2007
    Co-Authors: N. Giraud, M. Blackledge, A. Bockmann, L. Emsley
    Abstract:

    The effect of Nitrogen-15 proton-driven spin diffusion on quantitative (15)N T(1) measurements in solid proteins is investigated, and the impact on the measurement of dynamic parameters is assessed. A simple model of exchange between neighboring Nitrogens is used to reproduce the evolution of (15)N spin systems whose longitudinal relaxation rates and exchange rates are compatible with experimental measurements. We show that the induced error in the measured T(1) and its effect on the determination of dynamics parameters is likely to be less than the current experimental error. The use of deuterated protein samples is shown to have a small but sometimes visible effect, and may also considerably slow down or even suppress the exchange of magnetization due to spin diffusion.The effect of Nitrogen-15 proton-driven spin diffusion on quantitative (15)N T(1) measurements in solid proteins is investigated, and the impact on the measurement of dynamic parameters is assessed. A simple model of exchange between neighboring Nitrogens is used to reproduce the evolution of (15)N spin systems whose longitudinal relaxation rates and exchange rates are compatible with experimental measurements. We show that the induced error in the measured T(1) and its effect on the determination of dynamics parameters is likely to be less than the current experimental error. The use of deuterated protein samples is shown to have a small but sometimes visible effect, and may also considerably slow down or even suppress the exchange of magnetization due to spin diffusion.

  • The influence of Nitrogen-15 proton-driven spin diffusion on the measurement of Nitrogen-15 longitudinal relaxation times
    Journal of magnetic resonance (San Diego Calif. : 1997), 2006
    Co-Authors: N. Giraud, M. Blackledge, A. Bockmann, L. Emsley
    Abstract:

    The effect of Nitrogen-15 proton-driven spin diffusion on quantitative (15)N T(1) measurements in solid proteins is investigated, and the impact on the measurement of dynamic parameters is assessed. A simple model of exchange between neighboring Nitrogens is used to reproduce the evolution of (15)N spin systems whose longitudinal relaxation rates and exchange rates are compatible with experimental measurements. We show that the induced error in the measured T(1) and its effect on the determination of dynamics parameters is likely to be less than the current experimental error. The use of deuterated protein samples is shown to have a small but sometimes visible effect, and may also considerably slow down or even suppress the exchange of magnetization due to spin diffusion.

  • Quantitative analysis of backbone dynamics in a crystalline protein from Nitrogen-15 spin-lattice relaxation.
    Journal of the American Chemical Society, 2005
    Co-Authors: N. Giraud, M. Blackledge, A. Bockmann, M. Goldman, A. Lesage, F. Penin, L. Emsley
    Abstract:

    A detailed analysis of Nitrogen-15 longitudinal relaxation times in microcrystalline proteins is presented. A theoretical model to quantitatively interpret relaxation times is developed in terms of motional amplitude and characteristic time scale. Different averaging schemes are examined in order to propose an analysis of relaxation curves that takes into account the specificity of MAS experiments. In particular, it is shown that magic angle spinning averages the relaxation rate experienced by a single spin over one rotor period, resulting in individual relaxation curves that are dependent on the orientation of their corresponding carousel with respect to the rotor axis. Powder averaging thus leads to a nonexponential behavior in the observed decay curves. We extract dynamic information from experimental decay curves, using a diffusion in a cone model. We apply this study to the analysis of spin-lattice relaxation rates of the microcrystalline protein Crh at two different fields and determine differential dynamic parameters for several residues in the protein.

  • Quantitative analysis of backbone dynamics in a crystalline protein from Nitrogen-15 spin-lattice relaxation.
    Journal of the American Chemical Society, 2005
    Co-Authors: N. Giraud, M. Blackledge, A. Bockmann, M. Goldman, A. Lesage, F. Penin, L. Emsley
    Abstract:

    A detailed analysis of Nitrogen-15 longitudinal relaxation times in microcrystalline proteins is presented. A theoretical model to quantitatively interpret relaxation times is developed in terms of motional amplitude and characteristic time scale. Different averaging schemes are examined in order to propose an analysis of relaxation curves that takes into account the specificity of MAS experiments. In particular, it is shown that magic angle spinning averages the relaxation rate experienced by a single spin over one rotor period, resulting in individual relaxation curves that are dependent on the orientation of their corresponding carousel with respect to the rotor axis. Powder averaging thus leads to a nonexponential behavior in the observed decay curves. We extract dynamic information from experimental decay curves, using a diffusion in a cone model. We apply this study to the analysis of spin-lattice relaxation rates of the microcrystalline protein Crh at two different fields and determine differential dynamic parameters for several residues in the protein.A detailed analysis of Nitrogen-15 longitudinal relaxation times in microcrystalline proteins is presented. A theoretical model to quantitatively interpret relaxation times is developed in terms of motional amplitude and characteristic time scale. Different averaging schemes are examined in order to propose an analysis of relaxation curves that takes into account the specificity of MAS experiments. In particular, it is shown that magic angle spinning averages the relaxation rate experienced by a single spin over one rotor period, resulting in individual relaxation curves that are dependent on the orientation of their corresponding carousel with respect to the rotor axis. Powder averaging thus leads to a nonexponential behavior in the observed decay curves. We extract dynamic information from experimental decay curves, using a diffusion in a cone model. We apply this study to the analysis of spin-lattice relaxation rates of the microcrystalline protein Crh at two different fields and determine differential dynamic parameters for several residues in the protein.

N. Giraud - One of the best experts on this subject based on the ideXlab platform.

  • The influence of Nitrogen-15 proton-driven spin diffusion on the measurement of Nitrogen-15 longitudinal relaxation times.
    J Magn Reson, 2007
    Co-Authors: N. Giraud, M. Blackledge, A. Bockmann, L. Emsley
    Abstract:

    The effect of Nitrogen-15 proton-driven spin diffusion on quantitative (15)N T(1) measurements in solid proteins is investigated, and the impact on the measurement of dynamic parameters is assessed. A simple model of exchange between neighboring Nitrogens is used to reproduce the evolution of (15)N spin systems whose longitudinal relaxation rates and exchange rates are compatible with experimental measurements. We show that the induced error in the measured T(1) and its effect on the determination of dynamics parameters is likely to be less than the current experimental error. The use of deuterated protein samples is shown to have a small but sometimes visible effect, and may also considerably slow down or even suppress the exchange of magnetization due to spin diffusion.The effect of Nitrogen-15 proton-driven spin diffusion on quantitative (15)N T(1) measurements in solid proteins is investigated, and the impact on the measurement of dynamic parameters is assessed. A simple model of exchange between neighboring Nitrogens is used to reproduce the evolution of (15)N spin systems whose longitudinal relaxation rates and exchange rates are compatible with experimental measurements. We show that the induced error in the measured T(1) and its effect on the determination of dynamics parameters is likely to be less than the current experimental error. The use of deuterated protein samples is shown to have a small but sometimes visible effect, and may also considerably slow down or even suppress the exchange of magnetization due to spin diffusion.

  • The influence of Nitrogen-15 proton-driven spin diffusion on the measurement of Nitrogen-15 longitudinal relaxation times
    Journal of magnetic resonance (San Diego Calif. : 1997), 2006
    Co-Authors: N. Giraud, M. Blackledge, A. Bockmann, L. Emsley
    Abstract:

    The effect of Nitrogen-15 proton-driven spin diffusion on quantitative (15)N T(1) measurements in solid proteins is investigated, and the impact on the measurement of dynamic parameters is assessed. A simple model of exchange between neighboring Nitrogens is used to reproduce the evolution of (15)N spin systems whose longitudinal relaxation rates and exchange rates are compatible with experimental measurements. We show that the induced error in the measured T(1) and its effect on the determination of dynamics parameters is likely to be less than the current experimental error. The use of deuterated protein samples is shown to have a small but sometimes visible effect, and may also considerably slow down or even suppress the exchange of magnetization due to spin diffusion.

  • Quantitative analysis of backbone dynamics in a crystalline protein from Nitrogen-15 spin-lattice relaxation.
    Journal of the American Chemical Society, 2005
    Co-Authors: N. Giraud, M. Blackledge, A. Bockmann, M. Goldman, A. Lesage, F. Penin, L. Emsley
    Abstract:

    A detailed analysis of Nitrogen-15 longitudinal relaxation times in microcrystalline proteins is presented. A theoretical model to quantitatively interpret relaxation times is developed in terms of motional amplitude and characteristic time scale. Different averaging schemes are examined in order to propose an analysis of relaxation curves that takes into account the specificity of MAS experiments. In particular, it is shown that magic angle spinning averages the relaxation rate experienced by a single spin over one rotor period, resulting in individual relaxation curves that are dependent on the orientation of their corresponding carousel with respect to the rotor axis. Powder averaging thus leads to a nonexponential behavior in the observed decay curves. We extract dynamic information from experimental decay curves, using a diffusion in a cone model. We apply this study to the analysis of spin-lattice relaxation rates of the microcrystalline protein Crh at two different fields and determine differential dynamic parameters for several residues in the protein.

  • Quantitative analysis of backbone dynamics in a crystalline protein from Nitrogen-15 spin-lattice relaxation.
    Journal of the American Chemical Society, 2005
    Co-Authors: N. Giraud, M. Blackledge, A. Bockmann, M. Goldman, A. Lesage, F. Penin, L. Emsley
    Abstract:

    A detailed analysis of Nitrogen-15 longitudinal relaxation times in microcrystalline proteins is presented. A theoretical model to quantitatively interpret relaxation times is developed in terms of motional amplitude and characteristic time scale. Different averaging schemes are examined in order to propose an analysis of relaxation curves that takes into account the specificity of MAS experiments. In particular, it is shown that magic angle spinning averages the relaxation rate experienced by a single spin over one rotor period, resulting in individual relaxation curves that are dependent on the orientation of their corresponding carousel with respect to the rotor axis. Powder averaging thus leads to a nonexponential behavior in the observed decay curves. We extract dynamic information from experimental decay curves, using a diffusion in a cone model. We apply this study to the analysis of spin-lattice relaxation rates of the microcrystalline protein Crh at two different fields and determine differential dynamic parameters for several residues in the protein.A detailed analysis of Nitrogen-15 longitudinal relaxation times in microcrystalline proteins is presented. A theoretical model to quantitatively interpret relaxation times is developed in terms of motional amplitude and characteristic time scale. Different averaging schemes are examined in order to propose an analysis of relaxation curves that takes into account the specificity of MAS experiments. In particular, it is shown that magic angle spinning averages the relaxation rate experienced by a single spin over one rotor period, resulting in individual relaxation curves that are dependent on the orientation of their corresponding carousel with respect to the rotor axis. Powder averaging thus leads to a nonexponential behavior in the observed decay curves. We extract dynamic information from experimental decay curves, using a diffusion in a cone model. We apply this study to the analysis of spin-lattice relaxation rates of the microcrystalline protein Crh at two different fields and determine differential dynamic parameters for several residues in the protein.

Thomas Theis - One of the best experts on this subject based on the ideXlab platform.

  • Microtesla SABRE Enables 10% Nitrogen-15 Nuclear Spin Polarization
    Journal of the American Chemical Society, 2015
    Co-Authors: Thomas Theis, Roman V. Shchepin, Warren S. Warren, Milton L. Truong, Aaron M. Coffey, Kevin W. Waddell, Fan Shi, Boyd M. Goodson, Eduard Y. Chekmenev
    Abstract:

    Parahydrogen is demonstrated to efficiently transfer its nuclear spin hyperpolarization to Nitrogen-15 in pyridine and nicotinamide (vitamin B3 amide) by conducting “signal amplification by reversible exchange” (SABRE) at microtesla fields within a magnetic shield. Following transfer of the sample from the magnetic shield chamber to a conventional NMR spectrometer, the 15N NMR signals for these molecules are enhanced by ∼30,000- and ∼20,000-fold at 9.4 T, corresponding to ∼10% and ∼7% nuclear spin polarization, respectively. This method, dubbed “SABRE in shield enables alignment transfer to heteronuclei” or “SABRE-SHEATH”, promises to be a simple, cost-effective way to hyperpolarize heteronuclei. It may be particularly useful for in vivo applications because of longer hyperpolarization lifetimes, lack of background signal, and facile chemical-shift discrimination of different species.

  • microtesla sabre enables 10 Nitrogen 15 nuclear spin polarization
    Journal of the American Chemical Society, 2015
    Co-Authors: Thomas Theis, Roman V. Shchepin, Warren S. Warren, Milton L. Truong, Aaron M. Coffey, Kevin W. Waddell, Fan Shi, Boyd M. Goodson, Eduard Y. Chekmenev
    Abstract:

    Parahydrogen is demonstrated to efficiently transfer its nuclear spin hyperpolarization to Nitrogen-15 in pyridine and nicotinamide (vitamin B3 amide) by conducting “signal amplification by reversible exchange” (SABRE) at microtesla fields within a magnetic shield. Following transfer of the sample from the magnetic shield chamber to a conventional NMR spectrometer, the 15N NMR signals for these molecules are enhanced by ∼30,000- and ∼20,000-fold at 9.4 T, corresponding to ∼10% and ∼7% nuclear spin polarization, respectively. This method, dubbed “SABRE in shield enables alignment transfer to heteronuclei” or “SABRE-SHEATH”, promises to be a simple, cost-effective way to hyperpolarize heteronuclei. It may be particularly useful for in vivo applications because of longer hyperpolarization lifetimes, lack of background signal, and facile chemical-shift discrimination of different species.

Roman V. Shchepin - One of the best experts on this subject based on the ideXlab platform.

  • Direct Hyperpolarization of Nitrogen-15 in Aqueous Media with Parahydrogen in Reversible Exchange
    Journal of the American Chemical Society, 2017
    Co-Authors: Johannes F. P. Colell, Angus W. J. Logan, Roman V. Shchepin, Gerardo X. Ortiz, Qiu Wang, Meike Emondts, Kun Shen, Junu Bae, Peter Spannring, Steven J. Malcolmson
    Abstract:

    Signal amplification by reversible exchange (SABRE) is an inexpensive, fast, and even continuous hyperpolarization technique that uses para-hydrogen as hyperpolarization source. However, current SABRE faces a number of stumbling blocks for translation to biochemical and clinical settings. Difficulties include inefficient polarization in water, relatively short-lived 1H-polarization, and relatively limited substrate scope. Here we use a water-soluble polarization transfer catalyst to hyperpolarize Nitrogen-15 in a variety of molecules with SABRE-SHEATH (SABRE in shield enables alignment transfer to heteronuclei). This strategy works in pure H2O or D2O solutions, on substrates that could not be hyperpolarized in traditional 1H-SABRE experiments, and we record 15N T1 relaxation times of up to 2 min.

  • Generalizing, Extending, and Maximizing Nitrogen-15 Hyperpolarization Induced by Parahydrogen in Reversible Exchange
    The journal of physical chemistry. C Nanomaterials and interfaces, 2017
    Co-Authors: Johannes F. P. Colell, Angus W. J. Logan, Zijian Zhou, Roman V. Shchepin, Danila A. Barskiy, Gerardo X. Ortiz, Qiu Wang, Steven J. Malcolmson, Eduard Y. Chekmenev, Warren S. Warren
    Abstract:

    Signal Amplification by Reversible Exchange (SABRE) is a fast and convenient NMR hyperpolarization method that uses cheap and readily available para-hydrogen as a hyperpolarization source. SABRE can hyperpolarize protons and heteronuclei. Here we focus on the heteronuclear variant introduced as SABRE-SHEATH (SABRE in SHield Enables Alignment Transfer to Heteronuclei) and Nitrogen-15 targets in particular. We show that 15N-SABRE works more efficiently and on a wider range of substrates than 1H-SABRE, greatly generalizing the SABRE approach. In addition, we show that Nitrogen-15 offers significantly extended T1 times of up to 12 minutes. Long T1 times enable higher hyperpolarization levels but also hold the promise of hyperpolarized molecular imaging for several tens of minutes. Detailed characterization and optimization are presented, leading to Nitrogen-15 polarization levels in excess of 10% on several compounds.

  • Microtesla SABRE Enables 10% Nitrogen-15 Nuclear Spin Polarization
    Journal of the American Chemical Society, 2015
    Co-Authors: Thomas Theis, Roman V. Shchepin, Warren S. Warren, Milton L. Truong, Aaron M. Coffey, Kevin W. Waddell, Fan Shi, Boyd M. Goodson, Eduard Y. Chekmenev
    Abstract:

    Parahydrogen is demonstrated to efficiently transfer its nuclear spin hyperpolarization to Nitrogen-15 in pyridine and nicotinamide (vitamin B3 amide) by conducting “signal amplification by reversible exchange” (SABRE) at microtesla fields within a magnetic shield. Following transfer of the sample from the magnetic shield chamber to a conventional NMR spectrometer, the 15N NMR signals for these molecules are enhanced by ∼30,000- and ∼20,000-fold at 9.4 T, corresponding to ∼10% and ∼7% nuclear spin polarization, respectively. This method, dubbed “SABRE in shield enables alignment transfer to heteronuclei” or “SABRE-SHEATH”, promises to be a simple, cost-effective way to hyperpolarize heteronuclei. It may be particularly useful for in vivo applications because of longer hyperpolarization lifetimes, lack of background signal, and facile chemical-shift discrimination of different species.

  • microtesla sabre enables 10 Nitrogen 15 nuclear spin polarization
    Journal of the American Chemical Society, 2015
    Co-Authors: Thomas Theis, Roman V. Shchepin, Warren S. Warren, Milton L. Truong, Aaron M. Coffey, Kevin W. Waddell, Fan Shi, Boyd M. Goodson, Eduard Y. Chekmenev
    Abstract:

    Parahydrogen is demonstrated to efficiently transfer its nuclear spin hyperpolarization to Nitrogen-15 in pyridine and nicotinamide (vitamin B3 amide) by conducting “signal amplification by reversible exchange” (SABRE) at microtesla fields within a magnetic shield. Following transfer of the sample from the magnetic shield chamber to a conventional NMR spectrometer, the 15N NMR signals for these molecules are enhanced by ∼30,000- and ∼20,000-fold at 9.4 T, corresponding to ∼10% and ∼7% nuclear spin polarization, respectively. This method, dubbed “SABRE in shield enables alignment transfer to heteronuclei” or “SABRE-SHEATH”, promises to be a simple, cost-effective way to hyperpolarize heteronuclei. It may be particularly useful for in vivo applications because of longer hyperpolarization lifetimes, lack of background signal, and facile chemical-shift discrimination of different species.