The Experts below are selected from a list of 225 Experts worldwide ranked by ideXlab platform
Beat H. Meier - One of the best experts on this subject based on the ideXlab platform.
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PAIN with and without PAR: variants for third-spin assisted heteronuclear Polarization Transfer
Journal of Biomolecular NMR, 2013Co-Authors: Vipin Agarwal, Matthias Ernst, Mariana Sardo, Ingo Scholz, Anja Böckmann, Beat H. MeierAbstract:In this article, we describe third-spin assisted heteronuclear recoupling experiments, which play an increasingly important role in measuring long-range heteronuclear couplings, in particular ^15N–^13C, in proteins. In the proton-assisted insensitive nuclei cross Polarization (PAIN-CP) experiment (de Paëpe et al. in J Chem Phys 134:095101, 2011 ), heteronuclear Polarization Transfer is always accompanied by homonuclear Transfer of the proton-assisted recoupling (PAR) type. We present a phase-alternating experiment that promotes heteronuclear (e.g. ^15N → ^13C) Polarization Transfer while simultaneously minimizing homonuclear (e.g.^13C → ^13C) Transfer (PAIN without PAR). This minimization of homonuclear Polarization Transfer is based on the principle of the resonant second-order Transfer (RESORT) recoupling scheme where the passive proton spins are irradiated by a phase-alternating sequence and the modulation frequency is matched to an integer multiple of the spinning frequency. The similarities and differences between the PAIN-CP and this het-RESORT experiment are discussed here.
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PAIN with and without PAR: variants for third-spin assisted heteronuclear Polarization Transfer.
Journal of biomolecular NMR, 2013Co-Authors: Vipin Agarwal, Matthias Ernst, Mariana Sardo, Ingo Scholz, Anja Böckmann, Beat H. MeierAbstract:In this article, we describe third-spin assisted heteronuclear recoupling experiments, which play an increasingly important role in measuring long-range heteronuclear couplings, in particular (15)N-(13)C, in proteins. In the proton-assisted insensitive nuclei cross Polarization (PAIN-CP) experiment (de Paepe et al. in J Chem Phys 134:095101, 2011), heteronuclear Polarization Transfer is always accompanied by homonuclear Transfer of the proton-assisted recoupling (PAR) type. We present a phase-alternating experiment that promotes heteronuclear (e.g. (15)N → (13)C) Polarization Transfer while simultaneously minimizing homonuclear (e.g.(13)C → (13)C) Transfer (PAIN without PAR). This minimization of homonuclear Polarization Transfer is based on the principle of the resonant second-order Transfer (RESORT) recoupling scheme where the passive proton spins are irradiated by a phase-alternating sequence and the modulation frequency is matched to an integer multiple of the spinning frequency. The similarities and differences between the PAIN-CP and this het-RESORT experiment are discussed here.
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eMagRes - Adiabatic Polarization-Transfer Methods in MAS Spectroscopy
Encyclopedia of Magnetic Resonance, 2010Co-Authors: Matthias Ernst, Beat H. MeierAbstract:In an adiabatic implementation of Polarization-Transfer methods, the Hamiltonian is changed in a slow and adiabatic way such that the density operator follows the Hamiltonian and commutes with it at every point in time. Adiabatic Polarization Transfer relies on a sweep through a resonance condition and is less sensitive to experimental parameters and spin-system parameters than conventional “sudden” experiments where the density operator evolves under a static Hamiltonian. In powder samples adiabatic experiments result in higher Transfer efficiencies which can theoretically reach 100%. Keywords: MAS; homonuclear Polarization Transfer; adiabatic Polarization Transfer; rotational resonance; DREAM; cross Polarization; C7
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Adiabatic homonuclear Polarization Transfer in magic-angle-spinning solid-state NMR
Chemical Physics Letters, 1997Co-Authors: René Verel, Marc Baldus, M. Nijman, J. W. M. Van Os, Beat H. MeierAbstract:Abstract An adiabatic homonuclear Polarization-Transfer scheme is introduced. It involves an adiabatic passage through the rotational-resonance condition (APRR) experimentally realized by a ramp of the MAS speed. The APRR experiment is demonstrated to lead to a more complete Transfer and to be more broadbanded than the rotational-resonance experiment. APRR can be looked at as a prototype for a whole class of homonuclear adiabatic Polarization-Transfer schemes.
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Broadband Polarization-Transfer experiments for rotating solids
Chemical Physics Letters, 1994Co-Authors: Marc Baldus, Marco Tomaselli, Beat H. Meier, Richard R. ErnstAbstract:Abstract A new type of rotor-synchronized ‘R/L-driven’ Polarization-Transfer techniques is introduced and is shown to lead to efficient rare spin Polarization Transfer over a large range of chemical shifts. It is demonstrated that Polarization Transfer can proceed via a zero- or double-quantum mechanism depending on the design of the pulse sequence. It is shown experimentally that R/L-driven Polarization Transfer can be observed not only in isotopically enriched compounds but also in natural abundance (e.g. 13 C) samples.
Steffen J. Glaser - One of the best experts on this subject based on the ideXlab platform.
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Optimization of Electron–Nuclear Polarization Transfer
Applied Magnetic Resonance, 2008Co-Authors: Nikolas Pomplun, Björn Heitmann, Navin Khaneja, Steffen J. GlaserAbstract:Optimal-control-based numerical algorithms make it possible to explore the physical limits of dynamic nuclear Polarization. Examples of time-optimal and relaxation-optimized electron–nuclear Polarization Transfer experiments are presented for simple model systems consisting of an isolated electron–nuclear spin pair in the absence and presence of relaxation. The optimized pulse sequences are compared with conventional Transfer schemes, such as electron–nuclear cross Polarization and selective population inversion.
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optimization of electron nuclear Polarization Transfer
Applied Magnetic Resonance, 2008Co-Authors: Nikolas Pomplun, Björn Heitmann, Navin Khaneja, Steffen J. GlaserAbstract:Optimal-control-based numerical algorithms make it possible to explore the physical limits of dynamic nuclear Polarization. Examples of time-optimal and relaxation-optimized electron–nuclear Polarization Transfer experiments are presented for simple model systems consisting of an isolated electron–nuclear spin pair in the absence and presence of relaxation. The optimized pulse sequences are compared with conventional Transfer schemes, such as electron–nuclear cross Polarization and selective population inversion.
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Exploring the limits of Polarization Transfer efficiency in homonuclear three spin systems.
Journal of magnetic resonance (San Diego Calif. : 1997), 2006Co-Authors: Jorge L. Neves, Björn Heitmann, Navin Khaneja, Timo O. Reiss, Heloiza H. R. Schor, Steffen J. GlaserAbstract:The limits of Polarization Transfer efficiency are explored for systems consisting of three isotropically coupled spins 1/2 in the absence of relaxation. An idealized free evolution and control Hamiltonian is studied, which provides an upper limit of Transfer efficiency (in terms of Transfer amplitude and Transfer time) for realistic homonuclear spin systems with arbitrary Heisenberg-type coupling constants J12, J13, and J23. It is shown that optimal control based pulse sequences have significantly improved Transfer efficiencies compared to conventional Transfer schemes. An experimental demonstration of optimal Polarization Transfer is given for the case of the carbon spin system of fully 13C labelled alanine at 62.5 MHz Larmor frequency.
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Negative Polarization Transfer between a spin 1/2 and a spin 1
Chemical Physics Letters, 2000Co-Authors: Burkhard Luy, Steffen J. GlaserAbstract:Abstract Analytical coherence Transfer functions are presented for spin systems consisting of a spin 1/2 and a spin 1 under isotropic mixing conditions. Negative Polarization Transfer is found in theoretical and experimental Transfer functions for this simple two-spin system. This is in contrast to isotropic mixing experiments in spin systems consisting entirely of spins 1/2 for which five or more coupled spins are necessary to give rise to negative Polarization Transfer.
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Coupling Topology Dependence of Polarization-Transfer Efficiency in TOCSY and TACSY Experiments
Journal of Magnetic Resonance Series A, 1993Co-Authors: Steffen J. GlaserAbstract:Abstract The efficiency of selective and nonselective cross Polarization in homo- and heteronuclear liquid-state nuclear magnetic resonance spectroscopy is investigated. A general classification scheme for TOCSY (total correlation spectroscopy) and TACSY (tailored correlation spectroscopy) experiments is introduced based on characteristic effective zero-quantum coupling tensors. The efficiency of Polarization Transfer with respect to Transfer amplitude and Transfer time is quantified and presented in the form of maps as a function of the relative coupling constants in systems consisting of three coupled spins. Characteristic differences in the Polarization-Transfer efficiency of TOCSY and TACSY variants are revealed and analyzed. Significant implications of these results are discussed for spin systems of practical interest.
Vipin Agarwal - One of the best experts on this subject based on the ideXlab platform.
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PAIN with and without PAR: variants for third-spin assisted heteronuclear Polarization Transfer
Journal of Biomolecular NMR, 2013Co-Authors: Vipin Agarwal, Matthias Ernst, Mariana Sardo, Ingo Scholz, Anja Böckmann, Beat H. MeierAbstract:In this article, we describe third-spin assisted heteronuclear recoupling experiments, which play an increasingly important role in measuring long-range heteronuclear couplings, in particular ^15N–^13C, in proteins. In the proton-assisted insensitive nuclei cross Polarization (PAIN-CP) experiment (de Paëpe et al. in J Chem Phys 134:095101, 2011 ), heteronuclear Polarization Transfer is always accompanied by homonuclear Transfer of the proton-assisted recoupling (PAR) type. We present a phase-alternating experiment that promotes heteronuclear (e.g. ^15N → ^13C) Polarization Transfer while simultaneously minimizing homonuclear (e.g.^13C → ^13C) Transfer (PAIN without PAR). This minimization of homonuclear Polarization Transfer is based on the principle of the resonant second-order Transfer (RESORT) recoupling scheme where the passive proton spins are irradiated by a phase-alternating sequence and the modulation frequency is matched to an integer multiple of the spinning frequency. The similarities and differences between the PAIN-CP and this het-RESORT experiment are discussed here.
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PAIN with and without PAR: variants for third-spin assisted heteronuclear Polarization Transfer.
Journal of biomolecular NMR, 2013Co-Authors: Vipin Agarwal, Matthias Ernst, Mariana Sardo, Ingo Scholz, Anja Böckmann, Beat H. MeierAbstract:In this article, we describe third-spin assisted heteronuclear recoupling experiments, which play an increasingly important role in measuring long-range heteronuclear couplings, in particular (15)N-(13)C, in proteins. In the proton-assisted insensitive nuclei cross Polarization (PAIN-CP) experiment (de Paepe et al. in J Chem Phys 134:095101, 2011), heteronuclear Polarization Transfer is always accompanied by homonuclear Transfer of the proton-assisted recoupling (PAR) type. We present a phase-alternating experiment that promotes heteronuclear (e.g. (15)N → (13)C) Polarization Transfer while simultaneously minimizing homonuclear (e.g.(13)C → (13)C) Transfer (PAIN without PAR). This minimization of homonuclear Polarization Transfer is based on the principle of the resonant second-order Transfer (RESORT) recoupling scheme where the passive proton spins are irradiated by a phase-alternating sequence and the modulation frequency is matched to an integer multiple of the spinning frequency. The similarities and differences between the PAIN-CP and this het-RESORT experiment are discussed here.
Shanmin Zhang - One of the best experts on this subject based on the ideXlab platform.
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Absence of conservation laws and the reciprocity relation in Polarization‐Transfer experiments
Concepts in Magnetic Resonance, 1994Co-Authors: Shanmin Zhang, Ole W Sorensen, Richard R. ErnstAbstract:Conservation, creation, and destruction of Polarization in nuclear magnetic Polarization-Transfer experiments are discussed. In general, Polarization is not conserved during NMR pulse experiments, although a useful reciprocity relation is formulated. The features of Polarization-Transfer experiments are illustrated by liquid- and solid-state NMR.
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Quasi-Adiabatic Polarization Transfer in Solid-State NMR
Journal of Magnetic Resonance Series A, 1994Co-Authors: Shanmin ZhangAbstract:Abstract A modified Hartmann-Hahn type of cross-Polarization experiment is performed with varying amplitudes of the radiofrequency field in a descending or ascending order. The initial spin state evolves quasi-adiabatically in a zero-quantum space to a final state with a larger Polarization Transfer than that under the matched Hartmann-Hahn condition, which is predicted by a spin flip-flop model to have the most efficient Polarization Transfer. Experimental results recorded for a sample of ferrocene powder agree qualitatively with the theoretical prediction.
Richard R. Ernst - One of the best experts on this subject based on the ideXlab platform.
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Broadband Polarization-Transfer experiments for rotating solids
Chemical Physics Letters, 1994Co-Authors: Marc Baldus, Marco Tomaselli, Beat H. Meier, Richard R. ErnstAbstract:Abstract A new type of rotor-synchronized ‘R/L-driven’ Polarization-Transfer techniques is introduced and is shown to lead to efficient rare spin Polarization Transfer over a large range of chemical shifts. It is demonstrated that Polarization Transfer can proceed via a zero- or double-quantum mechanism depending on the design of the pulse sequence. It is shown experimentally that R/L-driven Polarization Transfer can be observed not only in isotopically enriched compounds but also in natural abundance (e.g. 13 C) samples.
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Absence of conservation laws and the reciprocity relation in Polarization‐Transfer experiments
Concepts in Magnetic Resonance, 1994Co-Authors: Shanmin Zhang, Ole W Sorensen, Richard R. ErnstAbstract:Conservation, creation, and destruction of Polarization in nuclear magnetic Polarization-Transfer experiments are discussed. In general, Polarization is not conserved during NMR pulse experiments, although a useful reciprocity relation is formulated. The features of Polarization-Transfer experiments are illustrated by liquid- and solid-state NMR.
