8S paramagnetic centres in molecular assemblies: possible effect of their proximity on the water proton relaxivity
✍ Scribed by Gaëlle M. Nicolle; Lothar Helm; André E. Merbach
- Publisher
- John Wiley and Sons
- Year
- 2003
- Tongue
- English
- Weight
- 216 KB
- Volume
- 41
- Category
- Article
- ISSN
- 0749-1581
- DOI
- 10.1002/mrc.1257
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✦ Synopsis
Abstract
EPR spectra of gadolinium chelates were recorded showing electron spin relaxation enhancement due to intramolecular Gd(III)–Gd(III) interaction. This enhancement was separated from other relaxation processes by replacing successively Gd(III) by the very similar Y(III). X‐band EPR line widths of the binuclear complex Gd~2~(OHEC)^2−^ increase by a factor of 1.2 to 1.8 with respect to YGd(OHEC)^2−^. Electron spin relaxation of Gd(III) bound on the surface of micelles formed by gadofluorine 8 increases linearly with the mole fraction of Gd(III) versus Y(III). It has been shown that the increase in electron spin relaxation due to Gd–Gd interactions decreases ^1^H relaxivity measured on surrounding water protons. In the case of gadolinium‐based magnetic resonance imaging contrast agents this effect can limit maximum relaxivity achieved by optimizing rotational tumbling and water exchange process. Copyright © 2003 John Wiley & Sons, Ltd.