cellular localisation of europium ( III ) coordination complexes †

Europium(III) complexes have been used extensively as stains for live cell uorescence microscopy. The development of responsive probes has allowed emissive europium(III) complexes to be used to measure the intracellular concentrations of a number of biologically relevant molecules, in addition to pH and pO2. Of critical importance for intracellular stains and probes, is the mechanism of uptake. In order for a complex to be used in cellulo, a comprehensive understanding of cell uptake and sub-cellular localisation is required to aid in the design of new probes to target particular organelles. Whilst the cell uptake mechanism of a wide range of 12-N4 based systems has been studied, a thorough investigation of the mechanism of internalisation of the EuroTrackerTM 9-N3 based systems with pyridylarylalkynyl chromophores has not been undertaken. A preliminary investigation suggested that macropinocytosis was involved in the uptake of these complexes, but the presence of other competing mechanisms was not ruled out. Here we report on the effect of probe chirality on the uptake process. Detailed studies of enantioselective behaviour in living cells have not been reported before. Since recognition in biological systems generally involves chiral proteins and glycoconjugates, the uptake of chiral probe species is expected to display chiral discrimination, due to differential diastereoisomeric interactions. Indeed, chiral discrimination of such complexes by sugars has been demonstrated in the resolution of the enantiomers by chiral HPLC with polysaccharide chiral stationary phases. Similarly, if the sub-cellular transport of the complexes is regulated by proteins, then variation in the