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.