Sensing Biologically Relevant Anions

Both Eu(III) excitation spectroscopy and emission spectroscopy gave information about solution speciation as a function of anion concentration as well as the structure of the bound anions [8]. Carbonate and lactate bound the most weakly = 35 mM, 16 mM, respectively). The lactate and carbonate complexes participate in both innersphere and outersphere interactions as shown by the presence of both the original excitation peak of Eu(STHP)(OH2) and a new red-shifted peak for the innersphere complex (Fig. 8.13a). A non-integral q number of 0.56 for lactate and 0.64 for carbonate is also consistent with a mixture of inner and outersphere complexes. Similarly, acetate, phosphate and methyl phosphate formed a mixture of outersphere and innersphere complexes depending on the conditions of the titrations. Only citrate appeared to form a predominantly innersphere complex with a formation constant of 17 pM (Fig. 8.13b). 

Emission spectroscopy showed that carboxy anions bound to Eu(STHP) gave uniquely different emission peak ratios compared to phosphate anions bound to Eu(STHP). Thus, 

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Andolina CM, Morrow JR. Lmninescence resonance energy transfer in heterodinuclear Ln(III) complexes for sensing biologically relevant anions. Eur J Inorg Chem. 2011 2011 154—164. 

While the above examples have focused on the sensing of structurally simple and biologically relevant anions, several examples of lanthanide complexes have emerged in the literature in the past decade where the sensing of large biologically relevant anionic... 

Unlike the Pfeiffer-induced systems discussed in Section 3.4.1, this section details some of the successful recent examples demonstrating the design principles for targeting anions and/or proteins that are of biological relevance [direct coordination to the metal centre of the chiral Ln(III)-based probes], followed by a survey of similar studies for analyte sensing (i.e. cations and/or proteins) in which the coordination occurs between the analytes and some of the antenna/receptor groups of the chiral Ln(III)-based probes. 

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