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001-es BibID:	BIBFORM018851
Első szerző:	Pálinkás Zoltán (vegyész)
Cím:	Kinetics of the Exchange Reactions between Gd(DTPA), Gd(BOPTA), and Gd(DTPA-BMA) Complexes, Used As MRI Contrast Agents, and the Triethylenetetraamine-Hexaacetate Ligand / Zoltán Pálinkás, Zsolt Baranyai, Ernő Brücher, Béla Rózsa
Dátum:	2011
ISSN:	0020-1669
Megjegyzések:	The kinetics of ligand exchange reactions occurring between the Gd(DTPA), Gd(BOPTA), and Gd(DTPA-BMA) complexes, used as contrast agents in MRI, and the ligand TTHA, have been studied in the pH range 6.5?11.0 by measuring the water proton relaxation rates at 25 ?C in 0.15 M NaCl. The rates of the reactions are directly proportional to the concentration of TTHA, indicating that the reactions take place with the direct attack of the HiTTHA(6?i)? (i = 0, 1, 2 and 3) species on the Gd3+ complexes, through the formation of ternary intermediates. The rates of the exchange reactions of the neutral Gd(DTPA-BMA) increase when the pH is increased from 6.5 to 9, because the less protonated HiTTHA(6?i)? species can more efficiently attack the Gd3+ complex. The rates of the exchange reactions of [Gd(DTPA)]2? and [Gd(BOPTA)]2? also increase from pH 8.5 to 11, but from 6.5 to 8.5 an unexpected decrease was observed in the reaction rates. The decrease has been interpreted by assuming the validity of general acid catalysis. The protons from the HiTTHA(6?i)? species (i = 2 and 3) can be transferred to the coordinated DTPA or BOPTA in the ternary intermediates when the dissociation of the Gd3+ complexes occurs faster. The kinetic inertness of Gd(DTPA), Gd(BOPTA), and Gd(DTPA-BMA) differs very considerably; the rates of the ligand exchange reactions of Gd(DTPA-BMA), thus the rates of its dissociation, are 2 to 3 orders of magnitude higher than those of Gd(DTPA) and Gd(BOPTA). The rates of the ligand exchange reactions increase with increasing concentration of the endogenous citrate, phosphate, or carbonate ions at a pH of 7.4, but the effect of citrate and phosphate is negligible at their physiological concentrations. The increase in the reaction rates at the physiological concentration of the carbonate ion is significant (20?60%), and the effect is the largest for the Gd(DTPA-BMA) complex.
Tárgyszavak:	Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:	Inorganic Chemistry. - 50 : 8 (2011), p. 3471-3478. -
További szerzők:	Baranyai Zsolt (1977-) (vegyész) Brücher Ernő (1935-) (vegyész) Rózsa Béla
Internet cím:	Szerző által megadott URL DOI Intézményi repozitóriumban (DEA) tárolt változat
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