Találati lista | Tudóstér

001-es BibID:	BIBFORM016454
Első szerző:	Baranyai Zsolt (vegyész)
Cím:	Equilibrium Studies on the Gd3+, Cu2+ and Zn2+ Complexes of BOPTA, DTPA and DTPA-BMA Ligands: Kinetics of Metal-Exchange Reactions of Gd(BOPTA) (2-) / Zsolt Baranyai, Zoltán Pálinkás, Fulvio Uggeri, Ernő Brücher
Dátum:	2010
ISSN:	1434-1948
Megjegyzések:	The stability and protonation constants of the complexes formed between the ligand BOPTA [H(5)BOPTA: 4-carboxy-5,8,11-tris(carboxymethyl)-1-phenyl-2-oxa-5,8,11-triazatrideca n-13-oic acid] and Gd3+, Cu2+, and Zn2+ have been determined by pH potentiometry (Gd3+, Zn2+) and spectrophotometry (Cu2+) at 25 degrees C and at constant ionic strength maintained by 0.15 M NaCl. For comparison, the stability and protonation constants of the complexes of Gd3+, Cu2+, and Zn2+ formed with DTPA and DTPA-BMA {H(5)DTPA: diethylenetriamine-N,N,N',N '',N ''-pentaacetic acid, H(3)DTPA-BMA: 2,2'-[(carboxymethyl)imino]bis[ethylenebis(methylcarbamoyl-methyl)imino] diacetic acid} have also been determined under similar conditions. The stability constants (log K-ML) of the complexes of BOPTA and DTPA are very similar, but in 0.15 m NaCl the protonation constants of the ligands (log K-j(H)) and the log K-ML values are lower than those obtained in 0.1 M KCl or Me4NCl by 0.3-0.9 log K units. The order of selectivity of the ligands for Gd3+ over Zn2+ is BOPTA > DTPA > DTPA-BMA. The complex [Cu(DTPA-BMA)](-) deprotonates in the pH range 7-10 with the dissociation of an amide NH group and the coordination of the amide N atom. The kinetics of the exchange/transmetallation reactions between the complex [Gd(BOPTA)](2-) and the metal ions Cu2+, Zn2+, and Eu3+ have been studied by spectrophotometry (Cu2+, Eu3+) and relaxometry (Zn2+) in the pH range 3.3-6 at 25 degrees C in 0.15 m NaCl. The reactions with Cu2+ and Zn2+ occur predominantly with direct attack of the metal ions on the [Gd(BOPTA)](2-) complex. The kinetic activity of Eu3+ is lower, and in the exchange reactions with Eu3+ the proton-assisted dissociation of [Gd(BOPTA)](2-) (which is followed by fast reaction between the free ligand and Eu3+) could be also investigated. The rate constants, characterizing the proton-assisted dissociation of [Gd(BOPTA)](2-) and the exchange reactions occurring with the direct attack of Cu2+, Zn2+, and Eu3+ on the complex, are lower by about 30-90% than the rate constants obtained earlier for similar transmetallation reactions of [Gd(DTPA)](2-). The half-time for the dissociation of [Gd(BOPTA)](2-) at pH 7.4 and at 25 degrees C in the presence of 1 x 10(-5) m Zn2+ and 1 x 10(-5) M Cu2+ is 169 h.
Tárgyszavak:	Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban Lanthanides Thermodynamics Kinetics Reaction mechanisms mri contrast agents diethylenetriaminepentaacetic acid stability ions dissociation dimeglumine constants biodistribution thermodynamics gadopentetate
Megjelenés:	European Journal of Inorganic Chemistry. - 13 (2010), p. 1948-1956. -
További szerzők:	Pálinkás Zoltán (1984-) (vegyész) Uggeri, Fulvio Brücher Ernő (1935-) (vegyész)
Internet cím:	DOI Intézményi repozitóriumban (DEA) tárolt változat
Borító:
Saját polcon:

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
Borító:
Saját polcon: