Many biological compounds present in cells, serum or other biological fluids are naturally fluorescent, and thus the use of conventional, prompt fluorophores leads to serious limitations in assay sensitivity due to the high background caused by the autofluorescence of the biological molecules to be assayed. The use of long-lived fluorophores combined with time-resolved detection (a delay between excitation and emission detection) minimizes prompt fluorescence interferences. Our trFluor™ probes enable time-resolved fluorometry (TRF) for the assays that require high sensitivity. trFluor™ probes have large Stokes shifts and extremely long emission half-lives when compared to more traditional fluorophores such as Alexa Fluor^® or cyanine dyes. Compared to the other TRF compounds, our trFluor™ probes have relatively high stability, high emission yield and the ability to be linked to biomolecules. In particular, our trFluor™ labeled streptavidin and anti-IgG (H+L) conjugates are increasingly used as second step reagents.

trFluor™ bioconjugates comprise proteins (streptavidin or anti-IgGs) with trFluor™ dye covalently attached as the time-resolved fluorescent tag. They are commonly used as second step reagents for indirect immunofluorescent staining, when used in conjunction with primary antibodies. They are very valuable tools for biotin developing biological assays and tests using TR-FRET platform. A variety of the complementary biotinylated reagents and primary antibodies are available from numerous commercial vendors.