Studies on the kinetic stabilities of the Gd3+ complexes formed with the N-mono(methylamide), N′-mono(methylamide) and N,N″-bis(methylamide) derivatives of diethylenetriamine-N,N,N′,N″,N″-pentaacetic acid

Sarka, Lajos; Burai, László; Király, Róbert; Zékány, László; Brücher, Ernő

doi:10.1016/s0162-0134(02)00418-x

Cited by 46 publications

(57 citation statements)

References 17 publications

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“…The results of our kinetic studies, however, show that the importance of the metal-assisted dissociation for [GdA C H T U N G T R E N N U N G (AAZTA)] À is very low and, at the low Cu 2 + and Zn 2 + concentrations indicated above, their contribution is negligible (the importance of the Zn 2 + -assisted transmetalation is generally lower than the Cu 2 + assisted one [25,26] ). By taking into account these considerations, for the reaction of [GdA C H T U N G T R E N N U N G (AAZTA)] À , the terms k Table 3, and also for [GdA C H T U N G T R E N N U N G (DTPA)] 2À , with the use of Equation (15), are shown in Table 4.…”

Section: H T U N G T R E N N U N G (Aazta)]mentioning

confidence: 63%

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Equilibrium and Kinetic Properties of the Lanthanoids(III) and Various Divalent Metal Complexes of the Heptadentate Ligand AAZTA

Baranyai

Uggeri

Giovenzana

et al. 2009

Chemistry A European J

127

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The heptadentate ligand 1,4-bis(hydroxycarbonylmethyl)-6-[bis(hydroxycarbonylmethyl)]amino-6-methylperhydro-1,4-diazepine (AAZTA) and its derivatives were recently reported to give stable complexes with Gd(3+) with superior efficiency as MRI contrast agents. Nevertheless, only preliminary data are available on the coordination behavior of this interesting ligand. In this work, thermodynamic and kinetic stability data are determined for the formation of complexes with AAZTA and the lanthanoid metal ions, and other divalent metal ions of interest for this application. The AAZTA ligand binds the lanthanoid ions with log K(ML) values of 17.53-21.85 with its affinity steadily increasing from La(3+) to Lu(3+), suggesting that the seven-membered skeleton is better suited to accommodate smaller metal ions. Even though the denticity is lower, the stability of the heavier lanthanoid complexes is comparable to those of the classical ligand diethylenetriaminepentaacetic acid (DTPA). The transmetalation reactions of [Gd(AAZTA)](-) with Cu(2+) and Eu(3+) predominantly occur through proton-assisted dissociation of the complex. The role of the direct attack of Cu(2+) or Eu(3+) in the exchange reactions is limited, although the formation of dinuclear complexes decreases the proton-assisted dissociation. Near physiological conditions, [Gd(AAZTA)](-) is significantly more inert than [Gd(DTPA)](2-), allowing its potentially safe use as contrast agent in magnetic resonance imaging.

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Section: H T U N G T R E N N U N G (Aazta)]mentioning

confidence: 63%

“…The kinetic stabilities of complexes are characterized either by the rates of their dissociation measured in 0.1 m HCl or by the rates of the transmetalation reaction, occurring in solutions with Zn 2 + and Cu 2 + or Eu 3 + . [24][25][26] 2À . [25] The rates of the transmetalation reactions [Eq.…”

Section: Resultsmentioning

confidence: 99%

Equilibrium and Kinetic Properties of the Lanthanoids(III) and Various Divalent Metal Complexes of the Heptadentate Ligand AAZTA

Baranyai

Uggeri

Giovenzana

et al. 2009

Chemistry A European J

127

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“…In the case of [Gd(L 2 )] 2-, the lower basicity of the donor groups results in lower ability of binuclear complex formation (see also the values of stability constants of dinuclear species, For the H 5 dtpa and its various amide derivatives, all the gadolinium() complexes have similar kinetic stability comparing to each other. [26][27][28]] Surprisingly, we found that the gadolinium() complexes with H 5 dtpa-analogues derived on the central nitrogen atom by the phosphorus acid pendant arm are much less kinetically stable with the halflife times about two to three orders of magnitude shorter. This can probably be attributed to a steric strain in the new complexes, which coordination sphere is not so compact and which can be attacked by a proton or by an additional metal ion.…”

Section: Dissociation Kineticsmentioning

confidence: 92%

“…[27,28] Therefore, the kinetic data had to be acquired by a stopped-flow technique. Dissociation reactions were performed in high excess (10-70×) of the concurrent metal ion (Cu 2+ or Eu 3+ ), ensuring pseudofirst-order reaction conditions, and in buffered solutions (pH in range 3.5-5.7).…”

Section: Dissociation Kineticsmentioning

confidence: 99%

Study of Thermodynamic and Kinetic Stability of Transition Metal and Lanthanide Complexes of DTPA Analogues with a Phosphorus Acid Pendant Arm

et al. 2006

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The thermodynamic and kinetic stabilities of the complexes of phosphonate and phenylphosphinate analogues of H 5 dtpa with selected transition-and lanthanide-metal ions are presented. Both phosphorus-containing ligands form thermodynamically very stable complexes, with stability constants comparable with or even higher than those reported for the parent H 5 dtpa. However, the kinetic inertness of their gadolinium(III) complexes against acid-and metal-assisted decomplexations is surprisingly much lower. The half-life times of gadolinium(III) complexes of the new ligands in the pres-

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“…The stability of the medical Gd 3 + complexes has to match severe criteria, verified by competitive potentiometry. [4,5] The architecture of the ligands has a strong influence on the efficiency--that is, the relaxivity-of the complexes in solution. From theoretical considerations one knows that complexes that are inject- À ) complexes in aqueous solution (DOTA = 1,4,7,10-tetrakis(carboxymethyl)-1,4,7,10-tetraazacyclododecane, DO3A =1,4,6-tris(carboxymethyl)-1,4,7,10-tetraazacyclododecane, DTPA = 1,1,4,7,7-pentakis(carboxymethyl)-1,4,7-triazaheptane, EGTA = 1,1,10,10-tetrakis(carboxymethyl)-1,10-diaza-4,7-dioxadecane).…”

Section: Introductionmentioning

confidence: 99%

MD Simulations of Acyclic and Macrocyclic Gd³⁺‐Based MRI Contrast Agents: Influence of the Internal Mobility on Water Proton Relaxivity

Yerly

Borel

Helm

et al. 2003

Chemistry A European J

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Classical molecular dynamics simulations with a force field adapted to the family of Gd(3+) polyaminocarboxylate complexes have been successfully applied on two macrocyclic ([Gd(DOTA)(H(2)O)](-) and [Gd(DO3A)(H(2)O)(2)]) and two acyclic ([Gd(DTPA)(H(2)O)](2-) and [Gd(EGTA)(H(2)O)](-)) complexes in aqueous solution (DOTA=1,4,7,10-tetrakis(carboxymethyl)-1,4,7,10-tetraazacyclododecane, DO3A=1,4,6-tris(carboxymethyl)-1,4,7,10-tetraazacyclododecane, DTPA=1,1,4,7,7-pentakis(carboxymethyl)-1,4,7-triazaheptane, EGTA=1,1,10,10-tetrakis(carboxymethyl)-1,10-diaza-4,7-dioxadecane). In both macrocylic complexes the Gd(3+) coordination polyhedron remains close to a monocapped square antiprism (MSA) during the entire simulation time. For the stereolabile acyclic complexes different interconverting sets of geometries are observed: three sets close to tricapped trigonal prisms (TTP) for [Gd(EGTA)(H(2)O)](-) and three sets intermediate between MSA and TTP (distorted C(2v) symmetry) for [Gd(DTPA)(H(2)O)](2-). The fast conformational changes observed in the acyclic complexes might weaken the hydration of the second water shell and therefore disfavour the outer-sphere relaxivity. Moreover, the motions of the chelate observed in both acyclic complexes involve the reorientation of the symmetry elements over time. This reorientation, occurring on a picosecond timescale, can be associated with the correlation time for modulation of the zero field splitting and might participate in the electron spin relaxation mechanisms of the Gd(3+) ion. The internal motion of the inner-sphere water molecule can be quantified by the ratio tau(R)(GD-HW)/tau(R)(GD-OW) which increases slightly from 0.7 for the acyclic to 0.8 for the macrocyclic complexes. This increase for the macrocylic chelates is favourable for a higher relaxivity and can be related to their rigidity. The water exchange rate on the four complexes has been related to the steric constraint of the ligand on the inner-sphere water molecule(s), which is inversely proportional to a geometrical descriptor, the solid angle psi. A range of psi values is given (2<

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Studies on the kinetic stabilities of the Gd3+ complexes formed with the N-mono(methylamide), N′-mono(methylamide) and N,N″-bis(methylamide) derivatives of diethylenetriamine-N,N,N′,N″,N″-pentaacetic acid

Cited by 46 publications

References 17 publications

Equilibrium and Kinetic Properties of the Lanthanoids(III) and Various Divalent Metal Complexes of the Heptadentate Ligand AAZTA

Equilibrium and Kinetic Properties of the Lanthanoids(III) and Various Divalent Metal Complexes of the Heptadentate Ligand AAZTA

Study of Thermodynamic and Kinetic Stability of Transition Metal and Lanthanide Complexes of DTPA Analogues with a Phosphorus Acid Pendant Arm

MD Simulations of Acyclic and Macrocyclic Gd³⁺‐Based MRI Contrast Agents: Influence of the Internal Mobility on Water Proton Relaxivity

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Studies on the kinetic stabilities of the Gd3+ complexes formed with the N-mono(methylamide), N′-mono(methylamide) and N,N″-bis(methylamide) derivatives of diethylenetriamine-N,N,N′,N″,N″-pentaacetic acid

Cited by 46 publications

References 17 publications

Equilibrium and Kinetic Properties of the Lanthanoids(III) and Various Divalent Metal Complexes of the Heptadentate Ligand AAZTA

Equilibrium and Kinetic Properties of the Lanthanoids(III) and Various Divalent Metal Complexes of the Heptadentate Ligand AAZTA

Study of Thermodynamic and Kinetic Stability of Transition Metal and Lanthanide Complexes of DTPA Analogues with a Phosphorus Acid Pendant Arm

MD Simulations of Acyclic and Macrocyclic Gd3+‐Based MRI Contrast Agents: Influence of the Internal Mobility on Water Proton Relaxivity

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MD Simulations of Acyclic and Macrocyclic Gd³⁺‐Based MRI Contrast Agents: Influence of the Internal Mobility on Water Proton Relaxivity