The Impact of Hydrogen Bonding on Amide 1H Chemical Shift Anisotropy Studied by Cross-Correlated Relaxation and Liquid Crystal NMR Spectroscopy

摘要: Site-specific H-1 chemical shift anisotropy (CSA) tensors have been derived for the well-ordered backbone amide moieties in B3 domain of protein G (GB3). Experimental input data include residual (RCSA), measured six mutants that align differently relative to static magnetic field when dissolved a liquid crystalline Pf1 suspension, and cross-correlated relaxation rates between H-1(N) CSA tensor either H-1-N-15, H-1-C-13', or H-1-C-13(alpha) dipolar interactions. Analyses with assumption is symmetric respect peptide plane (three-parameter fit) without this premise (five-parameter yield very similar results, confirming robustness experimental data, that, good approximation, one principal components orients orthogonal plane. are found deviate strongly from axial symmetry, most shielded component roughly parallel N-H vector, least DFT calculations on pairs N-methyl acetamide H-bonded geometries taken GB3 X-ray structure correlate indicate H-bonding effects dominate variations CSA. Using experimentally tensors, optimal interference effect needed narrowest TROSY line widths at 1200 MHz.