Determination of the relative orientation between 15N-1H dipolar coupling and 1H chemical shift anisotropy tensors under fast MAS solid-state NMR

In this work, we have proposed a proton-detected three-dimensional (3D) 15N -1H dipolar coupling (DIP)/1H chemical shift anisotropy (CSA)/1H chemical shift (CS) correlation experiment to measure the relative orientation between the 15N -1H dipolar coupling and the 1H CSA tensors under fast magic angle spinning (MAS) solid-state NMR. In the 3D correlation experiment, the 15N -1H dipolar coupling and 1H CSA tensors are recoupled using our recently developed windowless C-symmetry-based C313-ROCSA (re -coupling of chemical shift anisotropy) DIPSHIFT and C313-ROCSA pulse-based methods, respectively. The 2D 15N -1H DIP/1H CSA powder lineshapes extracted using the proposed 3D correlation method are shown to be sensitive to the sign and asymmetry of the 1H CSA tensor, a feature that allows the determination of the relative orientation between the two correlating tensors with improved accuracy. The experimental method developed in this study is demonstrated on a powdered U -15N L-Histidine.HCl center dot H2O sample. (c) 2023 Published by Elsevier Inc.

Automated summary

In this study, a proton-detected three-dimensional (3D) correlation experiment was proposed to measure the relative orientation between the 15N-1H dipolar coupling and the 1H CSA tensors under fast MAS solid-state NMR. The experiment utilized windowless C-symmetry-based C313-ROCSA DIPSHIFT and C313-ROCSA pulse-based methods to recouple the dipolar coupling and CSA tensors. The 2D 15N-1H DIP/1H CSA powder lineshapes extracted from the proposed 3D correlation method showed sensitivity to the sign and asymmetry of the 1H CSA tensor, allowing for improved accuracy in determining the relative orientation between the two tensors. The experimental method was demonstrated on a powdered U-15N L-Histidine.HCl·H2O sample.