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    Simple multidimensional NMR experiments to obtain different types of one-bond dipolar couplings simultaneously.
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    Keywords:
    Residual dipolar coupling
    Pulse sequence
    Magnetic dipole–dipole interaction
    Measurement of distances from dipolar couplings is essential for structural characterization, refinement and validation using the solid-state nuclear magnetic resonance (ssNMR) spectroscopy. Particularly, knowledge about NH dipolar interactions in biological solids is important for understanding the hydrogen (H)-bonding interactions, molecular geometry and spin dynamics. In this regard, we have proposed a proton-detected two-dimensional (2D) 15N-1H dipolar coupling/1H chemical shift correlation experiment using the C-symmetry based windowless recoupling of chemical shift anisotropy (ROCSA) in combination with the DIPSHIFT pulse-based method for the measurement of short NH distances in the isotopically labeled and naturally abundant biological solids at fast magic angle spinning (MAS) rates (40–70 kHz). Our proposed method results in undistorted recoupled 15N-1H dipolar coupling powder lineshapes that are free from the recoupled 1H CSA contributions under the 15N evolution, a feature that is essential for the measurement of NH distances with improved accuracy (± 500 Hz in terms of the NH dipolar couplings). The pulse sequence developed in the present study is also insensitive to the 1H–1H homonuclear dipolar interactions, relaxation effects owing to its constant-time implementation, and t1-noise from the fluctuations in the MAS.
    Magnetic dipole–dipole interaction
    Homonuclear molecule
    Residual dipolar coupling
    Chemical shift
    Pulse sequence
    Magic angle spinning
    Magic angle
    Coupling constant
    Homonuclear molecule
    Residual dipolar coupling
    Pulse sequence
    Magnetic dipole–dipole interaction
    Decoupling (probability)
    Magic angle
    Magic angle spinning
    Sequence (biology)
    Proton NMR
    Homonuclear molecule
    Magnetic dipole–dipole interaction
    Heteronuclear molecule
    Residual dipolar coupling
    Magic angle spinning
    Magic angle
    Pulse sequence
    A rapid spin–lattice 14N relaxation caused by an N–H proton transfer reaction in the solid state is likely to affect the 13C, 14N residual dipolar coupling generally observed in 13C CPMAS spectroscopy. A simple analysis is presented for studying the conditions under which the carbon resonances will be self-decoupled from the influence of 14N nuclei. The implications of the results as to the nature of the proton potential energy profile are also discussed.
    Residual dipolar coupling
    Magnetic dipole–dipole interaction
    Carbon-13
    Lattice (music)
    Citations (9)
    Heteronuclear molecule
    Dephasing
    Pulse sequence
    Pulsed field gradient
    Magnetic dipole–dipole interaction
    Residual dipolar coupling
    Decoupling (probability)
    Self-diffusion
    Molecular diffusion
    Citations (33)
    We show that 13C–1H dipolar couplings in fully protonated organic solids can be measured by applying a Symmetry-based Resonance-Echo DOuble-Resonance (S-REDOR) experiment at ultra-fast Magic-Angle Spinning (MAS). The 13C–1H dipolar couplings are recovered by using the R1253 recoupling scheme, while the interference of 1H–1H dipolar couplings are suppressed by the symmetry properties of this sequence and the use of high MAS frequency (65 kHz). The R1253 method is especially advantageous for large 13C–1H dipolar interactions, since the dipolar recoupling time can be incremented by steps as short as one rotor period. This allows a fine sampling for the rising part of the dipolar dephasing curve. We demonstrate experimentally that one-bond 13C–1H dipolar coupling in the order of 22 kHz can be accurately determined. Furthermore, the proposed method allows a rapid evaluation of the dipolar coupling by fitting the S-REDOR dipolar dephasing curve with an analytical expression.
    Magnetic dipole–dipole interaction
    Residual dipolar coupling
    Dephasing
    Heteronuclear molecule
    Magic angle spinning
    Magic angle
    Citations (26)