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Updated: May 10, 2026

Purification of Native Complexes for Structural Study Using a Tandem Affinity Tag Method
Published on: July 27, 2016
Bright mono-aqua europium complexes based on triazacyclononane that bind anions reversibly and permeate cells
Stephen J Butler1, Brian K McMahon, Robert Pal
1Department of Chemistry, Durham University, South Road, Durham, DH1 3LE, UK.
Abstract:
A series of five europium(III) complexes has been prepared from heptadentate N5O2 ligands that possess a brightness of more than 10 mM(-1) cm(-1) in water, following excitation over the range λ=330-355 nm. Binding of several oxy anions has been assessed by emission spectral titrimetric analysis, with the binding of simple carboxylates, lactate and citrate involving a common ligation mode following displacement of the coordinated water. Selectivity for bicarbonate allows the rapid determination of this anion in human serum, with K(d)=37 mM (295 K). The complexes are internalised quickly into mammalian cells and exhibit a mitochondrial localisation at early time points, migrating after a few hours to reveal a predominant lysosomal distribution. Herein, we report the synthesis and complexation behaviour of strongly emissive europium (III) complexes that bind oxy-anions in aqueous media with an affinity and selectivity profile that is distinctively different from previously studied systems.
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