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Gd Complexes (gd + complex)

Distribution by Scientific Domains

Chemistry	80%

Selected Abstracts

How to determine free Gd and free ligand in solution of Gd chelates.

CONTRAST MEDIA & MOLECULAR IMAGING, Issue 5 2006
A technical note
Abstract Gd(III) chelates are often used as reporting probes in magnetic resonance imaging applications. Their use relies on the assumption that their high stability ensures against the release of free ligand and free Gd3+ ions, which are both highly toxic to living systems. The presence of free Gd3+ ions may have a profound effect on the contrast in the MR image as they may form highly hydrated, macromolecular complexes endowed with very high relaxivity thus providing erroneous information on the extent of the contrast effect induced by the given reporting probe. Although the stability of a given complex may be high enough, the complexation step could not have been completed. Therefore any Gd complex preparation has to be carefully checked for the content of free ligand and free metal ions. Herein the currently used procedures that allow an assessment of the amounts of free metal ions and free ligand in a solution of a given Gd complex are described in detail. Copyright © 2006 John Wiley & Sons Ltd. [source]

Lanthanide-Based Conjugates as Polyvalent Probes for Biological Labeling

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 18 2008
Stéphanie Claudel-Gillet
Abstract A series of lanthanide complexes of [LnL(H2O)] composition, suitable for biological labeling has been studied, in which L is a strongly chelating ligand containing chromophoric bipyridylcarboxylate units and Ln = Sm, Eu, Gd, Tb, and Dy. For the Gd complex, a combined 17O NMR and 1H NMRD study has been performed. The water exchange rate obtained, kex298 = (5.2,±,0.6),×,106 s,1, is slightly higher than those for [Gd(dota)(H2O)], or [Gd(dtpa)(H2O)]2,. Transformation of the uncoordinated carboxylate function of the ligand into an activated ester ensures covalent linking of the complex to bovine serum albumine (BSA). The relaxivity properties of the Gd complex labeled on BSA revealed a limited increase of both longitudinal and transversal relaxivities. This can be related to the partial replacement of the inner-sphere water molecules by coordinating functions of the protein. Additionally, the Sm and Dy complexes are described and chemically characterized. Their photophysical properties were investigated by means of absorption, steady-state and time-resolved spectroscopy, evidencing efficient photosensitization of the lanthanide emission by ligand excitation (antenna effect). Luminescence lifetime measurements confirmed the presence of a water molecule in the first coordination sphere that partly explained the relatively poor luminescence properties of the Dy and Sm complexes in aqueous solutions. The spectroscopic properties of the series of complexes are questioned in terms of time-resolved acquisition techniques. Finally, their availability for use in time-resolved luminescence microscopy is demonstrated by staining experiments of rat brain slices, where the complex showed enhanced localization in some hydrophilic regions of the blood,brain barrier (BBB).(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

Characterization of gadolinium complexes for SAD phasing in macromolecular crystallography: application to CbpF

ACTA CRYSTALLOGRAPHICA SECTION D, Issue 8 2009
Rafael Molina
Seven Gd complexes were used in the preparation of heavy-atom derivatives for solving the structure of choline-binding protein F (CbpF), a 36,kDa surface protein from Streptococcus pneumoniae, by the SAD method. CbpF was used as a model system to analyse the phasing capability of each of the derivatives. Three different aspects have been systematically characterized: the efficacy of cocrystallization versus soaking in the binding of the different Gd complexes, their mode of interaction and a comparative study of SAD phasing using synchrotron radiation and using a rotating-anode generator. This study reveals the striking potential of these complexes for SAD phasing using a laboratory source and further reinforces their relevance for high-throughput macromolecular crystallography. [source]

Heavy-atom derivatives in lipidic cubic phases: results on hen egg-white lysozyme tetragonal derivative crystals with Gd-HPDO3A complex

ACTA CRYSTALLOGRAPHICA SECTION D, Issue 8 2004
Éric Girard
Gd-HPDO3A, a neutral gadolinium complex, is a good candidate for obtaining heavy-atom-derivative crystals by the lipidic cubic phase crystallization method known to be effective for membrane proteins. Gadolinium-derivative crystals of hen egg-white lysozyme were obtained by co-crystallizing the protein with 100,mM Gd-HPDO3A in a monoolein cubic phase. Diffraction data were collected to a resolution of 1.7 Å using Cu,K, radiation from a rotating-anode generator. Two binding sites of the gadolinium complex were located from the strong gadolinium anomalous signal. The Gd-atom positions and their refined occupancies were found to be identical to those found in derivative crystals of hen egg-white lysozyme obtained by co-crystallizing the protein with 100,mM Gd-HPDO3A using the hanging-drop technique. Moreover, the refined structures are isomorphous. The lipidic cubic phase is not disturbed by the high concentration of Gd-HPDO3A. This experiment demonstrates that a gadolinium complex, Gd-HPDO3A, can be used to obtain derivative crystals by the lipidic cubic phase crystallization method. Further studies with membrane proteins that are known to crystallize in lipidic cubic phases will be undertaken with Gd-HPDO3A and other Gd complexes to test whether derivative crystals with high Gd-site occupancies can be obtained. [source]