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Temperature and pH Dependence XAFS Study of Gd(DOTA)(-) and Gd(DTPA)(2)(-) Complexes: Solid State and Solution
Simone Bénazeth1, Juris Purans, Marie-Cécile Chalbot
1Laboratoire de Chimie Inorganique, UFR Pharmacie, Université Paris XI, 92296 Paris, France, LURE, Bat 209D, Université Paris XI, 91405 Orsay, France, Laboratoire de Chimie Bioorganique et Bioinorganique, Bat 420, Université Paris XI, 91405 Orsay, France, Laboratoire de Physique-biomathématiques, Faculté de pharmacie, Université Paris V, 75006 Paris, France, and Institute of Solid State Physics, University of Latvia, Kengaraga 8, 1063 Riga, Latvia.
This study used X-ray absorption spectroscopy to analyze gadolinium complexes Gd(DTPA)(2)(-) and Gd(DOTA)(-). Gd(DTPA)(2)(-) dissociates at low pH, while Gd(DOTA)(-) remains stable, revealing structural differences in solution.
Area of Science:
- Materials Science
- Inorganic Chemistry
- Biophysical Chemistry
Background:
- Gadolinium complexes are crucial in medical imaging and therapy.
- Understanding their structural stability in solution is vital for applications.
- Previous structural data primarily from crystalline states may not reflect solution behavior.
Purpose of the Study:
- To investigate the local structure and dynamics of Gd(DTPA)(2)(-) and Gd(DOTA)(-) complexes.
- To compare structural behavior in crystalline states versus aqueous solutions across varying pH and temperatures.
- To elucidate the impact of pH and temperature on the stability and coordination environment of gadolinium ions.
Main Methods:
- X-ray absorption spectroscopy (XAS) at the Gd L(3) edge.
- X-ray absorption fine structure (XAFS) analysis.
- Ab initio multiple scattering calculations for spectral interpretation.
Main Results:
- Local structures of Gd(DTPA)(2)(-) and Gd(DOTA)(-) were determined in crystalline and solution states.
- Gd(DTPA)(2)(-) showed progressive dissociation in acidic solutions (pH 0.15-1.5).
- Gd(DOTA)(-) exhibited remarkable stability across the studied pH range (1-1.5) and temperatures, with minor structural changes observed for both complexes with temperature.
Conclusions:
- Gd(DOTA)(-) demonstrates superior stability in acidic aqueous solutions compared to Gd(DTPA)(2)(-).
- The coordination environment of Gd(3+) ions in Gd(DOTA)(-) involves eight donor atoms (four O, four N) and one water molecule.
- The coordination environment of Gd(3+) ions in Gd(DTPA)(2)(-) involves eight donor atoms (five O, three N) and one water molecule, with observed dissociation at low pH.