A multinuclear NMR relaxometry study of ternary adducts formed between heptadentate Gd(III) chelates and L-lactate.
Dramatic relaxation enhancements of L-lactate resonances have been observed upon formation of ternary adducts with Gd(III) complexes of heptadentate DO3A and DO3A-like ligands (DO3A = 1,4,7,10-tetraazaciclododecane-1,4,7-triacetic acid). Detailed 1H and 17O NMR relaxometry investigations allow us to obtain structural, dynamic and thermodynamic information on the ternary complexes in which L-lactate acts as a bidentate ligand replacing two water molecules in the inner coordination sphere of the Gd(III) ion. It has been found that the exchange rate of the coordinated L-lactate is modulated by the structural and electronic properties of the parent Gd-heptacoordinated macrocyclic chelate. In addition to the characterisation of the relaxation behaviour of the 1H methyl resonance of L-lactate, this study has been extended to its 13C isomer (fully enriched at the three positions) and to the trifluoro-L-lactate. The obtained results may be relevant to the development of relaxation agents able to promote the relaxation enhancement of specific substrates detectable by in vivo magnetic resonance spectroscopy.
Terreno
Enzo
E
Dipartimento di Chimica I.F.M. Università degli Studi di Torino, Via P. Giuria 7, 10125 Torino, Italy.
Botta
Mauro
M
Boniforte
Patrizia
P
Bracco
Chiara
C
Milone
Luciano
L
Mondino
Bruna
B
Uggeri
Fulvio
F
Aime
Silvio
S
D002614:Chelating Agents / Q000737:chemistry*; D005682:Gadolinium / Q000737:chemistry*; D019344:Lactic Acid / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008958:Models, Molecular
D002614:Chelating Agents; D019344:Lactic Acid; D005682:Gadolinium