Determination of the rotation-diffusion tensor orientation from NMR¹³C-¹H cross-relaxation rates

Rotational Diffusion of Proteins in Nanochannels

“…It is to be noted that diffusion coefficients calculated based on rotations about individual principal axes of inertia may not represent the actual diffusion coefficients based on anisotropic tumbling since the protein’s principal axes of inertia may not be colinear with the principal axes of rotational diffusion. , The coefficients obtained from rotations of and about individual principal axes of inertia by isotropic rotation approach are thus unknown functions of actual diffusion coefficients from fully anisotropic rotational diffusion tensor . For assessing the anisotropic diffusion coefficients and checking the accuracy of isotropic diffusion coefficient, we calculated the fully anisotropic diffusion tensor based on the approach specified by Hummer et al Primarily, the reorientations of protein (considered as a rigid body) are obtained using the description of rotation matrices with respect to the starting structure of the protein for the entire trajectory.…”

Scalar Relaxation of the Second Kind: A Potential Source of Information on the Dynamics of Molecular Movements. 1. Investigation of Solution Reorientation of N-Methylpyridone and 1,3-Dimethyluracil Using Measurements of Longitudinal Relaxation Rates in the Rotating Frame

“…Such relaxation effects are, however, relatively weak and the results based on such data have to be treated with caution. Moreover, in the investigated molecules all C–H vectors lie in the molecular symmetry plane and all elementary dipolar relaxation mechanisms depend on the same combination of D z and D ⊥ diffusion coefficients . This feature in practice precludes application of the symmetrical top model, as separation of these two parameters and determination of their values is impossible.…”

“…Moreover, in the investigated molecules all C−H vectors lie in the molecular symmetry plane and all elementary dipolar relaxation mechanisms depend on the same combination of D z and D ⊥ diffusion coefficients. 36 This feature in practice precludes application of the symmetrical top model, as separation of these two parameters and determination of their values is impossible. Thus, it is apparent that inclusion of R 1,Q data for 14 N nuclei into the analysis is highly desirable for a complete description of the solution reorientation of our objects.…”

Heteronuclear Overhauser experiments for symmetric molecules

“…Moreover, this methodology was used successfully to extract structural and dynamical information from medium-sized molecules. 17,18 However, due to 13 C detection, this kind of experiment suffers from low sensitivity and requires (i) a highly concentrated sample or/and (ii) a substantial number of scans to ensure that some interactions are indeed accurately detected. (˛ x and (2˛ y are long radio-frequency pulses at high power level (1.5 ms and 3 ms respectively) which are placed at the beginning of the mixing time to saturate all 13 C magnetization.…”