Paramagnetic shift reagents

Figure 3. Monitoring the uptake of Li+ into human erythrocytes after incubation in media containing 2 mM Li+ using 7Li NMR spectroscopy. The signals corresponding to the intra-, and extracellular Li+ are separated by the presence of the paramagnetic shift reagent, Dy(P30io)2, the extracellular medium [34].

In addition to line broadening due to accelerated relaxation, paramagnetic salts and chelates give rise to isotropic shifts when added to samples containing molecules with groups susceptible to coordination with metal ions, e.g. —OH, —NH2, — SH, — COOH, -C = 0. The isotropic shift A of a nucleus i in a sample S is the difference between chemical shifts measured before and after addition of the paramagnetic shift reagent SR [103] ... 

Pro-R, configuration of an atom about a prochiral center Pro-5, configuration of an atom about a prochiral center PSR, paramagnetic shift reagent kx, B pulse causing a 180° rotation around the x axis (n/2)x, pulse causing a 90° rotation around the x axis... 

Stable metal complexes can be favorably formed when a bidentate metal-binding site is available, such as a- and -diketone moieties which are the tautomeric forms of a- and /3-ketoenols. Some /S-diketonate complexes of paramagnetic lanthanides such as Pr(III), Eu(III) and Yb(III) have been extensively utilized as paramagnetic shift reagents for structural assignment of molecules with complicated stereochemistry prior to 2D techniques in NMR spectroscopy. Their syntheses and application are discussed in separate chapters in this volume. The examples below provide some dynamic and structural basis for better understanding of metal enolates in biomolecules and biochemical processes. 

Paramagnetic shift reagents simplify complex spectra. 

Typical 13C spectra of 102-reacted CB before and after reduction are shown in Figure 5, with the following assignments of peaks based on paramagnetic shift reagent experiments and supported by analogies in the literature ... 

A combination of H-NMR and the paramagnetic shift reagent PrCls has been used to study the permeation of glycolic acid through LUVs of phosphatidylcholine at various... 

The enantiomer shift differences, AA5, are predominately induced by the differing equilibrium constants between the enantiomers and the paramagnetic shift reagent (45), (46). 

In principle, transport of any ion for which NMR-active isotopes and a suitable shift reagent exist can be investigated and in fact the use of NMR to observe transport of Na+, Cl , or Br has been suggested early on. Nonetheless, its routine use was mainly limited to Na NMR spectroscopy, in which external dysprosium triphosphate is used as a paramagnetic shift reagent to separate the chemical... 

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