1H line width dependence on MAS speed in solid state NMR – Comparison of experiment and simulation

Abstract

b s t r a c tRecent developments in magic angle spinning (MAS) technology permit spinning frequencies of !100 kHz. We examine the effect of such fast MAS rates upon nuclear magnetic resonance proton line widths in the multi-spin system of b-Asp-Ala crystal. We perform powder pattern simulations employing Fokker-Plank approach with periodic boundary conditions and 1 H-chemical shift tensors calculated using the bond polarization theory. The theoretical predictions mirror well the experimental results. Both approaches demonstrate that homogeneous broadening has a linear-quadratic dependency on the inverse of the MAS spinning frequency and that, at the faster end of the spinning frequencies, the residual spectral line broadening becomes dominated by chemical shift distributions and susceptibility effects even for crystalline systems.

Protein NMR Spectroscopy at 150 kHz Magic‐Angle Spinning Continues To Improve Resolution and Mass Sensitivity

“…Lastly, the polarization-and coherence-transfer processes during the NMR experiment have efficiencies that depend on the relaxation-rate constants R 2 ' and R 11 , which both are known to become smaller with faster spinning. [38,39] It has been demonstrated that the polarization-transfer efficiency at 90 kHz MAS is roughly between 0.20 and 0.90 for each transfer step [28] resulting, for experiments showing multiple transfers, in low overall efficiencies, often below 0.10, for example, 0.03 for an hcocaCBcacoNH 3D experiment [28] including seven polarizationtransfer steps. Improved polarization transfer at faster MAS thus has immense potential to enhance global sensitivity, notably in high-dimensional spectra, [40] which contain multiple transfer steps and will profit correspondingly stronger.…”

Quantifying proton NMR coherent linewidth in proteins under fast MAS conditions: a second moment approach

“…30 Such approaches may open up the possibility to approximately simulate also very large spin systems. 35,36 In this work, we present an alternative approach, which computes analytically or semi-analytically the linewidth using a moment expansion. This approach goes back to the moment expansion formulas derived by van Vleck.…”

Solid-state NMR spectroscopy: an advancing tool to analyse the structure and properties of metal–organic frameworks

“…18 Ultrafast spinning is particularly important for systems with strong homo-nuclear dipole couplings between more than two spins 19 like 1 H-rich solids. 20 Combination of MAS with cross-polarization (CP) 21 enables sensitive detection of well-resolved CP MAS NMR spectra 22 of intrinsically insensitive nuclei like 13 C, 15 N, or others. Cross-polarization is oen used in two-dimensional (2D) hetero-nuclear correlation (HETCOR) spectroscopy.…”