The magnetic relaxation dispersion

The sensitivity of the NMR experiment is strongly dependent on the magnetic field used for the experiment, which precludes measurements at low field strengths with high sensitivity. A solution to this problem is to make the magnetic field time-dependent either by moving the sample from 

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Kimmich and coworkers have studied the magnetic relaxation dispersion of liquids adsorbed on or contained in microporous inorganic materials such as glasses and packed silica (34-43) and analyze the relaxation dispersion data using Levy walk statistics for surface diffusion to build... 

Fig. 19. The magnetic relaxation dispersion for water proton in a Sephadex G-25 sample swollen to equilibrium at different values of pH at 298 K. The open circles are the relaxation rates for the methyl protons of dimethyl sulfoxide. The solid lines were computed from a two-stage exchange model 100).

In this connection, attention should be paid to an unusual NMR technique called nuclear magnetic relaxation dispersion (NMRD). In contrast with NMR spectroscopy, the NMRD signal arises from the nuclei of the abundant solvent molecules and not from the dissolved substances. The relaxation properties of the solvent molecules are profoundly modified if the solvent contains paramagnetic particles (see a review by Desreux 2005). A solvent molecule sails in the vicinity of an ion-radical and finds itself in the local magnetic field of this paramagnetic particle. Then, induced magnetism of the solvent molecule dissipates in the solvent bulk. This kind of relaxation seems to be registered by NMR. NMRD is applicable to studies on ion-radical solvation/desolvation, ion-pair dynamics, kinetics of ion-radical accumulation/consumption, and so on. 

The dependence of T (B) on the field B was soon nicknamed as the Ti dispersion curve or, more recently, as the Nuclear Magnetic Relaxation Dispersion (NMRD) profile. The first experimental curve of this type (Pig. 1) was published in 1950 by Ramsey and Pound (15,16). 

One effect of this rapid rotational motion is the loss of relaxivity at clinical frequencies. Figure 1 shows a Nuclear Magnetic Relaxation Dispersion (NMRD)... 

Nuclear Magnetic Relaxation Dispersion (NMRD). The Koenig Relaxometer Relaxivity as a function of field/frequency through analysis by simulation models r, q, rR, tm, ts for inner sphere, second sphere, and outer sphere water interactions. Also equilibrium constants for BPCA-protein and BPCA-cell interactions. 

Relaxation Measurements. Measurements of the magnetic fieldz dependence of the solvent water proton relaxation rate (T] l), i.e., nuclear magnetic relaxation dispersion (NMRD), were made by the field cycling method previously described (9,10). 

The proton nuclear magnetic relaxation dispersion profiles as well as the l70 temperature dependency were analysed. Best-fit parameters are given in Tables 7.18 and 7.19. 

A methodology for structural studies of the first and second coordination shells in [Cr(OH2)6]3+ and related complexes in aqueous solutions, based on multiple-scattering modeling of XAFS spectra, has been developed by Munoz-Paez and co-workers.523-525 Another technique, recently applied to studying of inner- and outer-sphere H20 coordination in [Cr(OH2)6]3+, is H nuclear magnetic relaxation dispersion (NMRD).526 Applications of different instrumental methods led to consistent results, indicating the presence of 13 1 H20 molecules with an average Cr "0 distance of 4.02 A in the second coordination shell of [Cr(OH2)6]3+ in aqueous solutions.9... 

Figure 1. Dispersion of 7/T/, the magnetic relaxation rate of solvent water protons, for a 65 mg/mL solution of alcohol-dehydrogenase from yeast, 160,000...

The nuclear magnetic relaxation dispersion is discussed in Section VI. 

F.G., and Halle, B. (1999) Water molecules in the binding cavity of intestinal fatty acid binding protein Dynamic characterization by water 0-17 and H-2 magnetic relaxation dispersion. Journal of Molecular Biology, 286, 233-246. 

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