Dipoles, relaxation mechanisms

Numerous studies of relaxation and molecular motion that measured Tj (and sometimes also T2) by conventional methods14 28 334-341 evaluated the contribution of the dipole-dipole relaxation mechanism from NOE measurements (Section IX) measurement of dynamic NOE (DNOE)71 yields both T and NOE factors in a single experiment342-344. DNOE appears to be the only conventional possibility to measure T in the cases when NOE nulls the signals [as in MeSi(OEt)3]335 345. 

NMR relaxation of protons in proteins is dominated by the dipole-dipole relaxation mechanism. For aromatic, geminal or methyl protons this involves protons separated by a fixed intemuclear distance, and for which the internal motion of the groups is simple and well understood (9-11). The NMR relaxation of protons relaxing via the intramolecular dipole-dipole mechanism [where the contributions of internal motion are not yet considered] is given by... 

It is well known that nuclear Overhauser effects arise from dipole-dipole relaxation mechanisms depending on r relationship (75). 

Nuclear Overhauser enhancements (NOEs) are a consequence of the dipole-dipole relaxation mechanism that operates through space (as opposed to the... 

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