Nuclear Overhauser effect steady-state

Under continuous uv irradiation, the observed steady-state polarization (whether by cw or by FT spectrometers) may be substantially modified by various nuclear relaxation processes. For example, Closs and Czeropski (35,36) have demonstrated that CIDNP can be transferred from a group of polarized nuclei to another group not originally polarized. Both the dipolar and the scalar relaxation mechanisms (of the nuclear Overhauser effects) can be operative. The extremely interesting case of intramolecular dipolar nuclear cross relaxation reported by Closs and Czeropski (35) involves the thermal reaction of... 

Before moving forward, the chemical biology reader should appreciate that Mz(f) polarisation and recovery towards steady state bulk magnetisation Mby spin-lattice relaxation are primarily indicative of changes in the levels of spin state occupancy. By contrast, My(f) coherence and evolution by spin-spin relaxation are both primarily indicative of transitions between spin state energy levels. In this context, the nuclear Overhauser effect (NOE) is a very important through-space effect in NMR spectroscopy that results directly from dipolar coupling-mediated spin-lattice relaxation. 

Ferrage F, Cowbum D, Ghose R (2009) Accurate sampling of high-frequency motions in proteins by steady-state (15)N- (1)H nuclear Overhauser effect measurements in the presence of cross-correlated relaxation. J Am Chem Soc 131 6048-6049... 

The second type of bistability is intrinsic to the conduction electron spins. Under saturation conditions, Overhauser effect is the primary condition for the observation of bistability. Under such a condition, the effective magnetic field, and hence the nuclear field takes two stable steady-state values for a given value of the external magnetic... 

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