Journal ArticleDOI
Heteronuclear decoupling in rotating solids
Andrew E. Bennett,Chad M. Rienstra,Michèle Auger,Michèle Auger,K. V. Lakshmi,K. V. Lakshmi,Robert G. Griffin +6 more
Reads0
Chats0
TLDR
In this article, a simple two pulse phase modulation (TPPM) scheme was proposed to reduce the residual linewidths arising from insufficient proton decoupling power in double resonance magic angle spinning (MAS) experiments.Abstract:
A simple two pulse phase modulation (TPPM) scheme greatly reduces the residual linewidths arising from insufficient proton decoupling power in double resonance magic angle spinning (MAS) experiments. Optimization of pulse lengths and phases in the sequence produces substantial improvements in both the resolution and sensitivity of dilute spins (e.g., 13C) over a broad range of spinning speeds at high magnetic field. The theoretical complications introduced by large homo‐ and heteronuclear interactions among the spins, as well as the amplitude modulation imposed by MAS, are explored analytically and numerically. To our knowledge, this method is the first phase‐switched sequence to exhibit improvement over continuous‐wave (cw) decoupling in a strongly coupled homogeneous spin system undergoing sample spinning.read more
Citations
More filters
Rigid Orthogonal Bis-TEMPO Biradicals with Improved Solubility for Dynamic Nuclear Polarization
Eric L. Dane,Björn Corzilius,Egon Rizzato,Pierre Stocker,Thorsten Maly,Albert A. Smith,Robert G. Griffin,Olivier Ouari,Paul Tordo,Timothy M. Swager +9 more
TL;DR: The results suggest that the orientation of the radicals is not dramatically affected by the oxidation state of the sulfur atoms in the biradicals, and it is concluded that a biradical polarizing agent containing a mixture of oxidation states can be used for improved solubility without a loss in performance.
Journal ArticleDOI
Correlation between 13C chemical shifts and the halogen bonding environment in a series of solid para-diiodotetrafluorobenzene complexes
TL;DR: In this article, the co-crystallization of para-diiodotetrafluorobenzene (p-DITFB) with ammonium and phosphonium halide (Cl− and Br−) salts afforded four new compounds that exhibit moderately strong halogen bonding interactions.
Journal ArticleDOI
Steric zipper of the amyloid fibrils formed by residues 109-122 of the Syrian hamster prion protein.
Shin-Wen Lee,Yun Mou,Shu-Yi Lin,Fang-Chieh Chou,Wei-Hsiang Tseng,Chun-hsien Chen,C.-Y. D. Lu,Steve S.-F. Yu,Jerry C. C. Chan +8 more
TL;DR: Solid-state NMR and MD simulation data indicate that a steric zipper can be formed in H1 fibrils near the region of the palindrome sequence.
Journal ArticleDOI
Inverse Detection and Heteronuclear Editing in 1H-15N Correlation and 1H-1H Double Quantum NMR Spectroscopy in the Solid State under Fast MAS
Ingo Schnell,B Langer,Shm Serge Söntjens,van Mhp Marcel Genderen,Rint P. Sijbesma,Hans-Wolfgang Spiess +5 more
TL;DR: Using recoupled polarization transfer (REPT), a heteronuclear 1H-15N single-quantum correlation (HSQC) experiment is presented whose symmetrical design allows the frequency dimensions to be easily interchanged and the sensitivity is experimentally found to be increased.
Journal ArticleDOI
Surfactant containing Si-MCM-41: An efficient basic catalyst for the Knoevenagel condensation
Leandro Martins,Tito José Bonagamba,Eduardo Ribeiro de Azevêdo,Pascal Bargiela,Dilson Cardoso +4 more
TL;DR: Si-MCM-41 molecular sieves, which are largely used in a number of acid and redox catalyzed reactions, as reported by the literature, were used as basic catalyst for the Knoevenagel condensation.
References
More filters
Journal ArticleDOI
Proton‐enhanced NMR of dilute spins in solids
TL;DR: In this article, the NMR signals of isotopically or chemically dilute nuclear spins S in solids can be enhanced by repeatedly transferring polarization from a more abundant species I of high abundance (usually protons) to which they are coupled.
Book
Principles of high-resolution NMR in solids
Abstract: 1 Introduction.- 2 Nuclear Spin Interactions in Solids.- 2.1 Basic Nuclear Spin Interactions in Solids.- 2.2 Spin Interactions in High Magnetic Fields.- 2.3 Transformation Properties of Spin Interactions in Real Space.- 2.4 Powder Spectrum Line Shape.- 2.5 The NMR Spectrum. Lineshapes and Moments.- 2.6 Magic Angle Spinning (MAS).- 2.7 Rapid Anisotropic Molecular Rotation.- 2.8 Line Shapes in the Presence of Molecular Reorientation.- 3 Multiple-Pulse NMR Experiments.- 3.1 Idealized Multiple-Pulse Sequences.- 3.2 The Four-Pulse Sequence (WHH-4).- 3.3 Coherent Averaging Theory.- 3.4 Application of Coherent Averaging Theory to Multiple-Pulse Sequences.- 3.5 Arbitrary Rotations and Finite Pulse Width in Multiple-Pulse Experiments.- 3.6 Second Averaging.- 3.7 The Influence of Pulse Imperfections on Multiple-Pulse Experiments.- 3.8 Resolution of Multiple-Pulse Experiments.- 3.9 Magic Angle Rotating Frame Line Narrowing Experiments.- 3.10 Modulation Induced Line Narrowing.- 3.11 Applications of Multiple-Pulse Experiments.- 4 Double Resonance Experiments.- 4.1 Basic Principles of Double Resonance Experiments.- 4.2 Cross-Polarization of Dilute Spins.- 4.3 Cross-Polarization Dynamics.- 4.4 Spin-Decoupling Dynamics.- 4.5 Application of Cross-Polarization Experiments.- 5 Two-Dimensional NMR Spectroscopy.- 5.1 Basic Principles of 2 D-Spectroscopy.- 5.2 2D-Spectroscopy of 13C-1H Interactions in Solids.- 5.3 Applications of 2D-Spectroscopy.- 6 Multiple-Quantum NMR Spectroscopy.- 6.1 Double-Quantum Decoupling.- 6.2 The Three-Level System Double Quantum Coherence.- 6.3 Multiple-Quantum Coherence.- 6.4 Selective Multiple-Quantum Coherence.- 6.5 Double-Quantum Cross-Polarization.- 7 Magnetic Shielding Tensor.- 7.1 Ramsey's Formula.- 7.2 Approximate Calculations of the Shielding Tensor.- 7.3 Proton Shielding Tensors.- 7.4 19F Shielding Tensors.- 7.5 13C Shielding Tensors.- 7.6 Other Shielding Tensors.- 8 Spin-Lattice Relaxation.- 8.1 Spin-Lattice Relaxation in the Weak Collision Limit.- 8.2 Spin-Lattice Relaxation in Multiple-Pulse Experiments.- 8.3 Application of Multiple-Pulse Experiments to the Investigation of Spin-Lattice Relaxation.- 8.4 Spin-Lattice Relaxation in Dilute Spin Systems.- 8.5 Selective Excitation and Spectral Diffusion.- 9 Appendix.- A Irreducible Tensor Representation of Spin Interactions.- B Rotations.- C General Line Shape Theory.- D Homogeneous, Inhomogeneous and Heterogeneous Lineshapes.- E Lineshape and Relaxation due to Fluctuating Chemical Shift Tensors.- F Time Evolution and Magnus Expansion.- G Coherent Versus Secular Averaging Theory.- H Applications of Average Hamiltonian Theory.- I Relaxation Theory.- 10 References.- 11 Subject Index.
Journal ArticleDOI
Nuclear Magnetic Resonance Spectra from a Crystal rotated at High Speed
TL;DR: In this article, it was shown that when these weak side-spectra are included the second moment does indeed remain invariant even though the second moments of the central portion, which is all that is observed experimentally, becomes smaller.
Journal ArticleDOI
Carbon-13 nuclear magnetic resonance of polymers spinning at the magic angle
Journal ArticleDOI
An improved sequence for broadband decoupling: WALTZ-16
TL;DR: In this paper, the effects of the proton irradiation sequence by means of a train of spin rotation operators, the overall effect at the end of the cycle being calculated by explicit matrix multiplication, the offset dependence of this proton response determined the residual splitting of the carbon-13 resonance and hence the effectiveness of the decoupling.