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trFluor™ Bioconjugates for Developing No Wash ELISA Assays

Time-Resolved Fluorescent Probes

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.

Key Features of trFluor™ Dyes

  • No fluoride addition is required
  • No enhancing solution is required
  • Available in a variety of reactive forms
  • Much easier to be conjugated to biomolecules
  • Much higher conjugation yield than other TRF dyes
  • Maximally excited by the common light sources at ~350 nm
  • trFluor™ Eu dye is optimized to pair with APC, iFluor® 647, TF5, Cy5®, DyLight™ 650 and Alexa Fluor® 647
  • trFluor™ Tb dye is optimized to pair with FITC, iFluor® 488, TF2, DyLight™ 488 and Alexa Fluor® 488


Table 1. trFluor™ Labeling Dyes

Cat No.
Product Name
Ex (nm)
Em (nm)
Unit Size
1433trFluor™ Eu succinimidyl ester 3466171 mg$547
1434trFluor™ Eu maleimide 346617100 ug$295
1443trFluor™ Tb succinimidyl ester 3305441 mgDiscontinued
1444trFluor™ Tb maleimide 330544100 ugDiscontinued


trFluor™ Dye-Labeled Secondary Detection 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.

trFluor™ Eu Goat Anti-Rabbit IgG conjugate
trFluor™ Tb Goat Anti-Rabbit IgG conjugate

Left: The excitation and emission spectra of trFluor™ Eu Goat Anti-Rabbit IgG conjugate in PBS buffer (pH 7.2). Right: The excitation and emission spectra of trFluor™ Tb Goat Anti-Rabbit IgG conjugate in PBS buffer (pH 7.2).


Table 2. trFluor™ Dye-Labeled Bioconjugates

Cat No.
Product Name
Ex (nm)
Em (nm)
Unit Size
16518trFluor™ Eu goat anti-mouse IgG (H+L) 346617100 ug$327
16668trFluor™ Eu goat anti-rabbit IgG (H+L) 346617100 ug$327
16725trFluor™ Eu goat anti-rabbit IgG (H+L) *Cross Adsorbed* 346617100 ug$437
16925trFluor™ Eu-streptavidin conjugate 346617100 ug$327
16519trFluor™ Tb goat anti-mouse IgG (H+L) 330544100 ug$327
16599trFluor™ Tb goat anti-mouse IgG (H+L) *Cross Adsorbed* 330544100 ug$437
16669trFluor™ Tb goat anti-rabbit IgG (H+L) 330544100 ug$327
16726trFluor™ Tb goat anti-rabbit IgG (H+L) *Cross Adsorbed* 330544100 ug$437
16926trFluor™ Tb-streptavidin conjugate 330544100 ugDiscontinued