In this paper, we present 3D chemical shift anisotropy (CSA)/dipolar coupling correlation experiments, based on γ-encoded R-type symmetry sequences. The γ-encoded correlation spectra are exquisitely sensitive to the relative orientation of the CSA and dipolar tensors and can provide important structural and dynamic information in peptides and proteins. We show that the firstorder (m = ±1) and second-order (m = ±2) Hamiltonians in the R-symmetry recoupling sequences give rise to different

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... tion patterns due to their different dependencies on the crystallite orientation. The relative orientation between CSA and dipolar tensors can be determined by fitting the corresponding correlation patterns. The orientation of 15 N CSA tensor in the quasi-molecular frame is determined by the relative Euler angles, α NH and β NH , when the combined symmetry schemes are applied for orientational studies of 1 H-15 N dipolar and 15 N CSA tensors. The correlation experiments introduced here work at moderate magic angle spinning frequencies (10-20 kHz) and allow for simultaneous measurement of multiple sites of interest. We studied the orientational sensitivity of γ-encoded symmetry-based recoupling techniques numerically and experimentally. The results are demonstrated on [ 15 N]-N-acetyl-valine (NAV) and N-formyl-Met-Leu-Phe (MLF) tripeptide. Correspondence to: Tatyana Polenova. Supporting Information: The recoupled lineshapes for different crystallite orientations in the laboratory frame produced by γ-encoded R18 1 7 and R14 2 3/5 . The effect of the Euler angle α NH on the 2D DIP/CSA lineshapes for the simulated DIP/CSA correlation spectra acquired with the γ-encoded R18 1 7 and R14 2 3/5 pulse sequences. Simulated R18 1 7 /R14 2 5 DIP/CSA correlation spectra for different relative tensor orientations. NIH Public Access