SYNTHESIS AND CHARACTERIZATION OF A NOVEL DTPA-LIKE GADOLINIUM(III) COMPLEX - A POTENTIAL REAGENT FOR THE DETERMINATION OF GLYCATED PROTEINS BY WATER PROTON NMR RELAXATION MEASUREMENTS

The synthesis of a novel DTPA-like ligand 2 containing two boronic acid phenylamide substituents and its Gd(III) complex 3 is reported. The measurement of the proton relaxation rate over the proton Larmor frequency range from 0.01 to 50 MHz of an aqueous solution of this paramagnetic complex suggests that it contains only one water molecule in its inner coordination sphere, as was previously found for the parent DTPA complex. Competition trials in presence of variable amounts of [Gd-EDTA]- afford a K(f) value of 2.0 x 10(16). Since the boronic functionalities form stable linkages with sin-diol moieties, the interaction of complex 3 with glycated albumin leads to the formation of a ternary albumin-3 complex. The large size of this adduct is responsible for a lengthening of the molecular reorientational time tau(R), which in turn results in an increase of water proton relaxation rate (R1p). The observed R1p enhancement then provides a direct evaluation of the extent of glycation of the albumin specimen.