The effects of intramolecular H-bond formation on the stability constant and water exchange rate of the Gd(III)-diethylenetriamine-N'-(3-amino-1,1-propylenephosphonic)-N, N,N'',N''-tetraacetate complex.
The binding interaction of metal chelates to biological macromolecules, though driven by properly devoted recognition synthons, may cause dramatic changes in some property associated with the coordination cage such as the thermodynamic stability or the exchange rate of the metal coordinated water. Such changes are due to electrostatic and H-bonding interactions involving atoms of the coordination cage and atoms of the biological molecule at the binding site. To mimic this type of H-bonding interactions, lanthanide(III) complexes with a DTPA-monophosphonate ligand bearing a propylamino moiety (H6NP-DTPA) were synthesized. Their thermodynamic stabilities and the exchange lifetime of the coordinated water molecule (for the Gd-complex) were compared with those of the analog complexes with DTPA and the parent DTPA-monophosphonate derivative (H6P-DTPA). It was found that the intramolecular H-bond between the epsilon-amino group and the phosphonate moiety in NP-DTPA complexes causes displacements of electric charges in their coordination cage that are markedly pH dependent. In turn, this affects the characteristic properties of the coordination cage. In particular it results in a marked elongation of the exchange lifetime of the coordinated water molecule.
Baranyai
Zsolt
Z
Department of Chemistry IFM and Molecular Imaging Center, University of Torino, Via. P. Giuria 7 10125 Torino, Italy.
Gianolio
Eliana
E
Ramalingam
Kondareddiar
K
Swenson
Rolf
R
Ranganathan
Ramachandran
R
Brücher
E
E
Aime
Silvio
S
D000085:Acetates / Q000737:chemistry*; D002614:Chelating Agents / Q000737:chemistry; D003287:Contrast Media / Q000494:pharmacology*; D005682:Gadolinium / Q000737:chemistry*; D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D008024:Ligands; D008670:Metals / Q000737:chemistry*; D008956:Models, Chemical; D009942:Organometallic Compounds / Q000494:pharmacology*; D063065:Organophosphonates / Q000737:chemistry; D004369:Pentetic Acid / Q000031:analogs & derivatives* / Q000737:chemistry* / Q000494:pharmacology; D013816:Thermodynamics; D014867:Water / Q000737:chemistry
D000085:Acetates; D002614:Chelating Agents; D003287:Contrast Media; D008024:Ligands; D008670:Metals; D009942:Organometallic Compounds; D063065:Organophosphonates; C525551:gadolinium(III) diethylenetriamine-N'-(3-amino-1,1-propylenephosphonic)-N,N,N'',N''-tetraacetate; D014867:Water; D004369:Pentetic Acid; D005682:Gadolinium