Lanthanides binding affinities

Fig. 6. Plot of association constants for Ln " " and [Ln(D02A)]" to DPA against lanthanide ionic radius, 0.2 M NaOAc, pH 7.5. The addition of D02A enhances dipicolinate binding affinity by an order of magnitude for most lanthanides investigated and by nearly two orders of magnitude for terbium (light gray).

Change in tbe analyte binding affinity (A o%K= ogK - ogK due to tbe ligand in comparison to tbe lanthanide alone. 

We plan to take advantage of ligand-induced enhancement of dipicolinate binding affinity to improve current bacterial spore detection technologies in two ways. The first involves appending terbium(macrocycle) complexes to solid polymer substrates to improve microscopy-based endospore assays. In a second method, we will bind lanthanide complexes to silica to concentrate dipicolinate from very dilute samples on colmnns. 

We have summarized the common attributes of ancillary ligands in improving detection techniques based on sensitized lanthanide luminescence and also introduced a new model for enhanced binding affinity. We suggest that binding affinities can be increased by an order of magnitude or more by ligand-induced anisotropy in... 

Since the mid 1970 s many different structures and classes of lanthanide chelates have been synthesised (Rgure 5). For high sensitivity assays the dissociation enhanced system is currently the best approach, however for screening assays where the sensitivity or detection limitation is not an issue the fluorescent chelates can be used to simplify the assay. Some of these chelates can be even used to develop homogeneous and non-separation assays. This assay format is essential for the measurement of a reaction where the components have only a weak binding affinity thus cannot withstand a wash or separation step. 

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