Relaxation relaxant agents

Tweedle, M. F. Relaxation Agents in NMR Imaging. In Lanthanide Probes in Life, Chemical and Earth Sciences Theory and Practice Btinzli, J.-C. G., Choppin, G. R., Eds. Amsterdam Elsevier, 1989 p 127. 

Manganese(II)-A/, A/r -dipyridoxylethylenediamine-A/r, AT-diacetate 5,5 -bis(phosphate) 75 (DPDP) is clinically used for enhancing contrast in the liver (detection of hepatocellular carcinomas) (312). Some dissociation of Mn(II) appears to occur in the liver, and enhancement can also be obtained in functional adrenal tissues (313). Manganese(II)-tetrasulfonated phthalocyanine also shows tumor localization properties and is a more efficient relaxation agent than the analogous Gd(III) complexes (314). 

Lauffer RB (1987) Paramagnetic metal complexes as water proton relaxation agents for NMR imaging theory and design. Chem. Rev. 87 901-927. 

Fig. 9. Variable temperature 0 NMR results (Bq = 14.1 T) for solutions containing Tb(C104)3 (0,DX Mg(C104)2 and Tb(C104)3 ( , ), and Mg(C104)2 and Mn(C104)2 (relaxation agent) (A). Full lines result from non-linear fitting using Kubo-Sack formalism and short-dashed lines were calculated by an approximate 3-site Swift and Connick method [Ref. (40)].

Figure 3 presents the NMRD curves of Pu " " (5/ , Hs/2) and Np (5/, %/2)-These two ions have non-spherically symmetric distribution of their unpaired electronic spins. Also included is the NMRD curve of Pr which is the lanthanide analog of Pu " " (12). All the ions are very poor relaxation agents... 

To reduce the nuclei s Tx relaxation time, relaxation agents are used. Relaxation agents are usually transition metal complexes, primarily ferric ethylenediaminetetraacetate or chromium acetylacetonate. Transfer of en-... 

The T relaxation agent increased the sensitivity of the NMR instrument by decreasing several of the mono- and diester phosphate relaxation times by factors of 2-5. In this way the delay time between scans was decreased (43). This change permits an increase in the number of scans observed per unit time. Although the presence of ferric ions creates the potential for precipitation of phosphorus-iron complexes, the addition of a large molar excess of ethylenediaminetetraacetate (EDTA) relative to ferric ions prevented precipitation, even over a large pH region (44). 

Matrix Effects. pH. Numerous factors such as sample pH, ionic strength, humic substances, and relaxation agents can modify the NMR spectrum. For example, monoester phosphate chemical shifts are pH-de-pendent (44-46), and we showed (44) for several monoester phosphates that as the sample pH is increased, their chemical shifts also increase (Figure 3). This behavior is caused by the ability of monoester phosphates to undergo protonation-deprotonation. Because the monoester phosphate chemical shift is pH-dependent, the curves resulting from plotting pH versus chemical shift are analogous to a titration curve. Thus, monoester phosphate pKa values can be measured from these pH-chemical shift curves (44-46). 

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