DELFIA^® Eu-DTPA Amino Chelate is optimized for the europium labeling of proteins and peptides for use in dissociation-enhanced time resolved fluorometric assays, where especially high chelate stability is required. It is recommended for assays where chelate has to be stable in in vivo conditions (e.g. pharmacokinetics) or assays where high concentrations of competing chelating agents may be present. The amino group reacts with free carboxyl groups on the proteins and peptides, forming stable, covalent bond.

The DTPA-chelates can be used in DELFIA^® separation assays where the concentration of chelating agents is <10 mM, pH>6.5, and the assay temperature is <70°C. They can stand 2 to 3 mmol EDTA when pH is 7.5 or higher. The enhancement time using a DELFIA^® shaker is 25 minutes. Iodoacetamido activated chelates, react primarily with free cysteines on the compound to be labeled.

DELFIA® (dissociation-enhanced lanthanide fluorescence immunoassay) is a time-resolved fluorescence (TRF) intensity technology. Assays are designed to detect the presence of a compound or biomolecule using lanthanide chelate labeled reagents, separating unbound reagent using wash steps. DELFIA assays are flexible, compatible with a variety of plate readers, and, as this is a wash-based technology, compatible with most sample types. The technology is based on fluorescence of lanthanide chelates (Europium, Samarium, and Terbium). The fluorescence decay time of these lanthanide chelate labels is much longer than traditional fluorophores, allowing efficient use of temporal resolution for reduction of autofluorescent background. The large Stokes’ shift (difference between excitation and emission wavelengths) and the narrow emission peaks contribute to increasing signal-to-noise ratio. Sensitivity is further increased because of the dissociation-enhancement principle: the lanthanide chelate is dissociated and a new highly fluorescent chelate is formed into a protective micellar solution. DELFIA lanthanide chelates require this dissociation/enhancement step for fluorescence (induced by addition of DELFIA Enhancement solution, DELFIA Inducer, and DELFIA Enhancer as appropriate to the particular lanthanide chelate).