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001-es BibID:	BIBFORM067453
Első szerző:	Baranyai Zsolt (vegyész)
Cím:	Equilibrium and NMR Relaxometric Studies on the s-Triazine-Based Heptadentate Ligand PTDITA Showing High Selectivity for Gd3+ Ions / Zsolt Baranyai, Lorenzo Tei, Giovanni B. Giovenzana, Ferenc K. Kálmán, Mauro Botta
Dátum:	2012
ISSN:	0020-1669
Megjegyzések:	A complete potentiometric and NMR relaxometric solution study on the heptadentate 2,2·,2ı,2·ı-[(6-piperidinyl-1,3,5-triazine-2,4-diyl)dihydrazin-2-yl-1-ylidene]tetraacetic acid (PTDITA) ligand has been carried out. This ligand is based on the 1,3,5-triazine ring with two hydrazine-N,N-diacetate groups in positions 2 and 4 and a piperidine moiety in position 6. The introduction of the triazine ring into the ligand backbone is expected to modify its flexibility and then to affect the stability of the corresponding complexes with transition-metal and lanthanide ions. Thermodynamic stabilities have been determined by pH potentiometry, UV spectrophotometry, and 1H NMR spectroscopy for formation of the complexes with Mg2+, Ca2+, Cu2+, Zn2+, La3+, Gd3+, and Lu3+ ions. PTDITA shows a good binding affinity for Gd3+ (logK = 18.49, pGd = 18.6) and an optimal selectivity for Gd3+ over the endogenous Ca2+, Zn2+, and Cu2+ (Ksel = 6.78 ? 107), which is 3 orders of magnitude higher that that reported for Gd(DTPA) (Ksel = 2.85 ? 104). This is mainly due to the lower stability of the CuII- and ZnII(PTDITA) complexes compared to the corresponding DTPA complexes, which suggests an important role of the triazine ring on the selectivity for the Gd3+ ion. The relaxometric properties of Gd(PTDITA) have been investigated in aqueous solution by measuring the 1H relaxivity as a function of the pH, temperature, and magnetic field strength (nuclear magnetic relaxation dispersion profile). Variable-temperature 17O NMR data have provided direct information on the kinetic parameters for exchange of the coordinated water molecules. A simultaneous fit of the data suggests that the high relaxivity value (r1 = 10.2 mM?1 s?1) is a result of the presence of two inner-sphere water molecules along with the occurrence of relatively slow rotation and electronic relaxation. The water residence lifetime, 298?M = 299 ns, is quite comparable to that of clinically approved magnetic resonance imaging contrast agents. The displacement of the inner-sphere water molecules by bidentate endogeneous anions (citrate, phosphate, and carbonate) has also been evaluated by 1H relaxometry. In general, the binding interaction is markedly weak, and only in the case of citrate, a ca. 35% decrease in relaxivity was observed in the presence of 60 equiv of the anion. Phosphate and carbonate also interact with the paramagnetic ion, likely as monodentate ligands, but formation of the ternary complex is accompanied by a modest increase of r1 due to the contribution of second-sphere water molecules.
Tárgyszavak:	Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban Heptadentate Ligand Equilibrium NMR Relaxometry gadolinium Molekulatudomány
Megjelenés:	Inorganic Chemistry 51 : 4 (2012), p. 2597-2607. -
További szerzők:	Tei, Lorenzo Giovenzana, Giovanni Battista Kálmán Ferenc K. (1978-) (vegyész) Botta, Mauro
Pályázati támogatás:	OTKA-83253 OTKA EU FP6 European Imaging Laboratories Egyéb TÁMOP-4.2.1/B-09/1/KONV-2010-0007 TÁMOP Kémiai vizsgálatok az orvosi képalkotó diagnosztikában használt fémkomplexek fejlesztésére
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001-es BibID:	BIBFORM067302
035-os BibID:	(WoS)000388546800022 (Scopus)84993990174
Első szerző:	Garda Zoltán (vegyész)
Cím:	Physico-chemical properties of MnII complexes formed with cis- and trans-DO2A : thermodynamic, electrochemical and kinetic studies / Zoltán Garda, Attila Forgács, Quyen N. Do, Ferenc K. Kálmán, Sarolta Timári, Zsolt Baranyai, Lorenzo Tei, Imre Tóth, Zoltán Kovács, Gyula Tircsó
Dátum:	2016
ISSN:	0162-0134 1873-3344
Megjegyzések:	Manganese (MnII) is a promising alternative to gadolinium (GdIII) as a magnetic resonance imaging (MRI) agent. Unlike gadolinium, this biogenic metal might be better tolerated by the body, reducing the risk of toxicity associated with dissociation of the complex. Herein we report detailed equilibrium and kinetic studies performed with MnII complexes of 1,4,7,10-tetraazacyclododecane-1,4-diacetic acid (1,4-DO2A or cis-DO2A) and 1,4,7,10-tetraazacyclododecane-1,7-diacetic acid (1,7-DO2A or trans-DO2A). The protonation constants of the ligands as well as stability constants of their MnII complexes have been determined by pH-potentiometry. The stability constants of [Mn(cis-DO2A)] are slightly higher than those of [Mn(trans-DO2A)] (log KMnL = 15.68 and 15.22, respectively). Cyclic voltammetric (CV) experiments performed on [Mn(cis-DO2A)] and [Mn(trans-DO2A)] revealed quasireversible systems with a half-wave potential of + 636 and + 705 mV versus Ag/AgCl, respectively. These values indicate that the MnII ion in these complexes is more stabilized against the oxidation than in [Mn(EDTA)]2 ?. The kinetic inertness of the complexes has been studied in transmetallation reactions with CuII or ZnII ions. Kinetic measurements indicate that both MnII complexes primarily undergo acid catalyzed dissociation and positions of the acetate pendant arms do not influence kinetic inertness. The inertness of these complexes is comparable to that of [Mn(NOTA)]? (NOTA = 1,4,7-triazacyclononane-1,4,7-triacetic acid) and about twenty times lower than that of [Mn(DOTA)]2 ? (DOTA = 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid). In conclusion, [Mn(cis-DO2A)] displays some very interesting features (thermodynamic and redox stability as well as kinetic inertness) which makes this complex a promising platform for the development of more efficient MnII complexes as alternatives to Gd-based MRI agents.
Tárgyszavak:	Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban folyóiratcikk Magnetic resonance imaging Contrast agents (CAs) Manganese Thermodynamic stability Inertness Electrochemistry
Megjelenés:	Journal of Inorganic Biochemistry. - 163 (2016), p. 206-213. -
További szerzők:	Forgács Attila (1988-) (vegyész) Do, Quyen N. (1975-) (vegyész) Kálmán Ferenc K. (1978-) (vegyész) Timári Sarolta (1984-) (vegyész, kémia tanár) Baranyai Zsolt (1977-) (vegyész) Tei, Lorenzo Tóth Imre (1950-) (vegyész) Kovács Zoltán (1963-) (vegyész, angol szakfordító) Tircsó Gyula (1977-) (vegyész, kémia tanár)
Pályázati támogatás:	OTKA-84291 OTKA OTKA-109029 OTKA TÁMOP 4.2.4. A/2-11-1-2012-0001 TÁMOP COST TD1004 Action "Theragnostics Imaging and Therapy: An Action to Develop Novel Nanosized Systems for Imaging-Guided Drug Delivery" Egyéb Bólyai János Kutatási Ösztöndíj MTA
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001-es BibID:	BIBFORM067454
Első szerző:	Tei, Lorenzo
Cím:	Solution properties of the Ln(III) complexes of a novel octadentate chelator with rigidified iminodiacetate arms / Lorenzo Tei, Zsolt Baranyai, Claudio Cassino, Marianna Fekete, Ferenc K. Kálmán, Mauro Botta
Dátum:	2012
ISSN:	1477-9226
Megjegyzések:	A novel octadentate ligand derived from the core structure of EGTA (ethyleneglycol-bis(2-aminoethylether)-N,N,N·,N·-tetraacetic acid) with two piperidine-cis-dicarboxylic acid moieties spaced by a triethylenedioxy chain (L1) has been synthesised with the aim to assess the effect of the structural rigidity on the thermodynamic and kinetic stabilities of its LnIII complexes. The stability constants of [Ln(L1)]? complexes show a weaker binding affinity for Ln3+ ions of L1 than EGTA. On the other hand, the selectivity of L1 for Ca2+ over Mg2+ is one of the highest ever reported. The kinetic inertness has been also investigated and faster rates of both acid catalysed and metal assisted decomplexation have been measured for [Gd(L1)]? as compared to [Gd(EGTA)]?. The 1H- and 13C NMR spectra of the diamagnetic La3+, Y3+ and Lu3+ complexes in aqueous media show pronounced stereochemical rigidity and the occurrence of a structural change across the lanthanide series. Finally, a complete 1H and 17O NMR relaxometric study indicates that [Gd(L1)]? possesses a nine-coordinate ground state with one inner coordination sphere water molecule characterized by a fast rate of exchange (298kex = 59 ? 106 s?1).
Tárgyszavak:	Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban lanthanide octadentate chelator rigidified iminodiacetate arms thermodynamic stability relaxometry
Megjelenés:	Dalton Transactions 41 (2012), p. 12797-12806. -
További szerzők:	Baranyai Zsolt (1977-) (vegyész) Cassino, Claudio Fekete Marianna Kálmán Ferenc K. (1978-) (vegyész) Botta, Mauro
Pályázati támogatás:	COST Action D38 Egyéb HU11MO2-TET_10-1-2011-0202 Egyéb
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001-es BibID:	BIBFORM018852
Első szerző:	Tei, Lorenzo
Cím:	Mn(ii) complexes of novel hexadentate AAZTA-like chelators : a solution thermodynamics and relaxometric study / Lorenzo Tei, Giuseppe Gugliotta, Marianna Fekete, Ferenc K. Kálmán, Mauro Botta
Dátum:	2011
ISSN:	1477-9226
Megjegyzések:	Three novel chelators based on the 6-amino-6-methylperhydro-1,4-diazepine scaffold and possessing three pendant N-acetic or N-?-methylacetic acid have been synthesised. The ligands contain six donor atoms for complexation of MnII ions and thus potentially leave an additional site for coordination of a water molecule. The protonation constants of the ligands and the stability constants of their complexes formed with MnII ion were determined by pH-potentiometric titrations in 0.15 M NaCl solution at 25 ?C and compared to those of the parent AAZTA ligand (AAZTA = 6-amino-6-methylperhydro-1,4-diazepine tetraacetic acid). In spite of the similar value of the total basicity (?log K), the values of the stability constants of the MnIIAAZTA-like complexes are more than three orders of magnitude lower than that of MnAAZTA (log KMnL = 14.19). A detailed 1H and 17O NMR relaxometric study was carried out on the MnII complexes in aqueous solution as a function of pH, temperature and magnetic field strength. The 1H NMRD profiles of all the complexes show a similar shape, typical of low-molecular weight systems, but amplitudes that markedly differ to indicate a different degree of hydration. A similar behaviour is shown by the 17O NMR transverse relaxation rates and chemical shift data as a function of temperature. The experimental data can be rationalised by considering the presence in solution of a mixture of two isomeric species differing in coordination number (7 and 6) and in the number (1 and 0) of bound water molecules. Whereas this type of coordination equilibrium has been previously reported for lanthanide(III) complexes, it is observed for the first time on MnII chelates.
Tárgyszavak:	Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:	Dalton Transactions. - 40 : 9 (2011), p. 2025-2032. -
További szerzők:	Gugliotta, Giuseppe Fekete Marianna Kálmán Ferenc K. (1978-) (vegyész) Botta, Mauro
Pályázati támogatás:	ESF COST Action D38 Egyéb
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