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Magnetic field dependence of solvent proton relaxation rates induced by Gd 3+ and Mn 2+ complexes of various polyaza macrocyclic ligands: Implications for NMR imaging
Author(s) -
Geraldes C. F. G. C.,
Sherry A. D.,
Brown R. D.,
Koenig S. H.
Publication year - 1986
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.1910030207
Subject(s) - chemistry , ethylenediaminetetraacetic acid , chelation , ligand (biochemistry) , proton , dota , solvent , relaxation (psychology) , ion , rotational correlation time , proton nmr , nuclear magnetic resonance , coordination sphere , chemical shift , crystallography , inorganic chemistry , stereochemistry , molecule , organic chemistry , social psychology , psychology , biochemistry , physics , receptor , quantum mechanics
The magnetic field dependence of the solvent water proton longitudinal relaxation rate 1/ T 1 (the NMRD profile) has been measured for solutions of chelates of Gd 3+ and Mn 2+ ions with two different polyaza macrocyclic ligands: 1, 4, 7‐triazacyclononane‐ N , N ′, N ″,‐triacetic acid (NOTA) and 1, 4, 7, 10‐tetraazacyclododecane‐ N , N ′, N ″, N ‴,‐tetraacetic acid (DOTA). Studies were carried out mainly near physiological pH, but the pH dependence was also examined in some cases. The results are compared with published data for complexes of Gd 3+ and Mn 2+ ions with ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetie acid (DTPA). Competition experiments for the NOTA and DOTA chelates with EDTA and DTPA were also performed. It is found that, over the field range in which NMR imaging is currently being done, different symmetries of otherwise similar chemical ligands can alter 1/ T 1 of solvent protons by factors of up to three. The ligand environment can influence the relaxation times of the electronic spin moments of the ions, as well as their coordination number, thereby changing both the inner and outer sphere contributions to the relaxivities of the complexes. The relevance of these results to questions of efficiency and toxicity of these chelates as agents for enhancement of contrast in NMR images is discussed. © 1986 Academic Press, Inc.