Phosphorus magnetic relaxation measurements

It should be realized, however, that chemical-shift anisotropy is not the sole mechanism that can cause relaxation for phosphoryl moieties or phos-phoproteins. Proton-phosphorus dipole-dipole relaxation mayplayarole, especially at lower magnetic field strength, and it is necessary to unravel the two contributions in order to be able to deduce motional characteristics from relaxation measurements. Under conditions of nonextreme narrowing ( Tc 1), where cu is the resonance frequency and the rotational correlation time, a condition that will generally hold for most phosphoproteins with immobilized phosphate residues, the following equations apply (Vogel et al, 1982). [For a more complete discussion, see Hull and Sykes (1975) Shindo (1980) and Chapter 13 Hart, Chapter 11 James, Chapter 12.)... 

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