17O-NMR, EPR and NMRD Characterization of [Gd(DTPA-BMEA)(H2O)]: A Neutral MRI Contrast Agent

Abstract

A study including variable‐temperature and ‐pressure, multiple‐field 17O NMR, EPR and NMRD has been performed on the MRI contrast agent, [Gd(DTPA‐BMEA)(H2O)]. The water exchange rate [kex298 = (0.39 ± 0.02) × 106 s−1] and the activation volume (ΔV≠ = +7.4 ± 0.4 cm3 mol−1), hence the mechanism, are identical to those for [Gd(DTPA‐BMA)(H2O)]. The longer rotational correlation time of [Gd(DTPA‐BMEA)(H2O)], as obtained from a global analysis of 17O‐NMR, EPR and NMRD data, and compared to that of [Gd(DTPA‐BMA)(H2O)], can be explained by water molecules hydrogen‐bonded to the ether oxygen atoms of the ligand side chain.

High-field pulsed EPR and ENDOR of Gd3+ complexes in glassy solutions

“…We have assumed, however, that the HFI distribution was mostly related to the anisotropic HFI. On the basis of this assumption and on the Gd-O distance determined by 170 ENDOR at W-band [22], a model of Gd-water coordination was devel- 9. Solid trace, the difference ENDOR spectrum of MS-325 obtained in the same way as the difference spectrum of Gd aquo complex shown in Fig.…”

“…As a result of the importance of these compounds in medicine and because of the complexity of the factors that define relaxivity, there have been numerous investigations into the magnetic and structural characteristics of Gd 3" complexes [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. Usually these investigations were performed in liquid solutions (e.g., nuclear magnetic resonance, neutron diffraction) [5][6][7] or in single crystals (X-ray crystallography) [8,9]. Both types of studies provide useful information about the structural and magnetic properties of the Gd 3+ complexes, but there is a substantial difference between these two approaches.…”

Joint analysis of ESR lineshapes and 1H NMRD profiles of DOTA-Gd derivatives by means of the slow motion theory

“…Powell et al 48 were the first to apply the SBM theory to the combined data sets for a number of Gd(III) complexes, with moderate success. Similar approaches were also adopted for other Gd(III) chelates by Toth et al 49 and, more recently ZithaBovens et al 50 The improved perturbation theory for electron spin relaxation 19,20 turned out to be more successful for the aqueous Gd(III) ion 21,22,51,52 and other small Gd(III) complexes. 53 Larger complexes, with electron spin relaxation outside of the Redfield limit, can be expected to be more difficult.…”

Optimising the design of paramagnetic MRI contrast agents: influence of backbone substitution on the water exchange rate of Gd-DTPA derivatives

“…Efforts are thus devoted to optimise the water residence time, s M , and therefore to alleviate the limitation of the complex's relaxivity. Amide linkages have to be avoided since they are known to prolong the water residence time [6][7][8][9][10][11][12][13][14]. On the contrary, a C4-substitution of the ethylenic bridge of DTPA by an ethoxybenzyl group, a benzyl, or a MAGMA (2004) Optimising the design of paramagnetic MRI contrast agents: influence of backbone substitution on the water exchange rate of Gd-DTPA derivatives (4,4-diphenylcyclohexyl)phosphanooxymethyl substituent has been shown to decrease the water exchange by 25-42% [15][16][17].…”

“…Efforts are thus devoted to optimise the water residence time, s M , and therefore to alleviate the limitation of the complex's relaxivity. Amide linkages have to be avoided since they are known to prolong the water residence time [6][7][8][9][10][11][12][13][14]. On the contrary, a C4-substitution of the ethylenic bridge of DTPA by an ethoxybenzyl group, a benzyl, or a MAGMA (2004) 16: 235-245 Abstract Among other factors influencing the residence time of the coordinated water (s M…”