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Nicolle, GM ; Toth, E ; Schmitt-Willich, H ; Raduchel, B ; Merbach, AE

The impact of rigidity and water exchange on the relaxivity of a dendritic MRI contrast agent

Chemistry-A European Journal 8 (5) 1040-1048

par Administrateur - publié le

Abstract :

Variable-temperature, multiple magnetic field O-17 NMR, EPR and variable-temperature H-1 nuclear magnetic relaxation dispersion (NMRD) measurement techniques have been applied to Gadomer 17, a new dendritic contrast agent for magnetic resonance imaging. The macromolecule bears 24 Gd(dota)-monoamide chelates (dota = N,N’,N",N"’,-tetracarboxymethyl-1,4,7,10-tetraazacyclododecane) attached to a lysine-based dendrimer. 170 NMR and H-1 NMRD data were analysed simultaneously by incorporating the Lipari-Szabo approach for the description of rotational dynamics. The water exchange rate k(ex)(298) was found to be (1.0 +/- 0. 1) x 10(6) s(-1), a value similar to ex those measured for other Gd(dota) monoamide complexes, and the activation parameters DeltaH = 24.7 +/- 1.3 kJ mol(-1) and DeltaS* = -47.4 +/- 0.2 JK(1) mol(-1).