NMR Relaxation in Multipolar AMX Systems under Spin-Locking Conditions

13C NMR Relaxation Analysis of Protein GB3 for the Assessment of Side Chain Dynamics Predictions by Current AMBER and CHARMM Force Fields

“…It may be noted that there was no evidence for elevated R 2 values at these well-ordered methylene positions. That observation is consistent with the relaxation interference effects that occur between the 2 H quadrupole and the 2 H– 13 C dipole interactions , having been efficiently suppressed by the simultaneous application of 2 H and 13 C spin lock fields during the transverse relaxation pulse experiments. , …”

“…Interference due to the 2 H− 13 C interactions can be suppressed by the application of spin lock fields. 53,54 In part, the selection of the GB3 protein for the experimental substantiation of the proposed analysis was based on the fact that near room temperature the NMR spectra of GB3 do not exhibit evidence of slow conformational transitions that would give rise to either resonance doubling or conformational exchange line broadening. It may be noted that NMR relaxation measurements in supercooled solution do indicate conformational exchange line broadening in the first β-turn of GB3 (Gly 9 to Lys 13) that when extrapolated to 25 °C predicts a transition time of ∼1 μs which is too rapid to alter the observed R 2 rates via this line broadening mechanism.…”

“…That observation is consistent with the relaxation interference effects that occur between the 2 H quadrupole and the 2 H− 13 C dipole interactions 69,70 having been efficiently suppressed by the simultaneous application of 2 H and 13 C spin lock fields during the transverse relaxation pulse experiments. 53,54 Optimization of NMR relaxation predictions at methylene positions was carried out in two steps. Initially for each methylene bond vector, the geminal 1 H− 13 C and 2 H− 13 C relaxation effects were modeled using a single set of (S f ) values and the bond vector-specific rotational diffusion decay constant for the 1 H− 13 C vector.…”

“…Using spectral selection against the 1 H 2 - 13 C spin systems, only signals from the 1 H– 13 C– 2 H isotopomers are observed. Interference due to the 2 H– 13 C interactions can be suppressed by the application of spin lock fields. , …”

Nuclear magnetic relaxation of spinI=1/2 scalar coupled to a quadrupolar nucleus in the presence of cross-correlation effects

“…As a rule, the spin systems with spin I = 1/2 are studied. However, the NMR study of the relaxation of large biomolecules having low mobility is problematic because the line width broadening induced by the dipolar interaction results in the resonance overlap [1][2][3]. The possibilities of NMR spectroscopy are confined by the molecular size of about 30 kDa.…”