Description
Streptavidin has been labeled with Terbium cryptate to be used as the donor fluorophore in HTRF immunoassays. Biotin binds to Streptavidin with high affinity (Ka=1015M-1). The binding is rapid and stable, making the reagent an ideal choice for use in a variety of assays such as enzyme assays, protein-protein binding assays and molecular biology assays. The reagent is compatible with assays prepared with homemade buffer or with ready-to-use catalog buffers such as the HTRF PPI Terbium detection buffer.
HTRF assays offer many advantages over other technologies:
Homogeneous add-and-read format
No wash steps
Low background
Straightforward miniaturization from 96- or 384-well microplates to high density assay formats such as 384-well low volume and 1536-well plates
Stable signal, providing flexibility in time of readout or size of assays
Assay principle
In an HTRF interaction assay, one partner is labeled (directly or indirectly) with the donor, and the other with the acceptor (again, directly or indirectly). The intensity of the signal is proportional to the binding of the 2 partners. In the example shown here: Streptavidin-Tb cryptate binds to the biotinylated tagged partner A while partner B* binds to a specific Ab labeled with an HTRF acceptor. *partner B can also be biotinylated, tagged, Fc fused. In these cases, use the corresponding HTRF reagent (anti-Tag, anti-species, protA, Streptavidin) labeled with acceptor for the detection.
Assay protocol
The example on the right describes the protocol using a 20 µL final assay volume for detecting an interaction between a biotinylated-tagged partner A and a non-tagged partner B*. Dispense the 2 partners (10 µL), incubate, add Streptavidin-Tb cryptate (5 µL) and anti-partner B labeled with acceptor (5 µL), incubate and read. *partner B can also be tagged, Fc fused or directly labeled. In these cases use for the detection, the corresponding HTRF reagent (anti-Tag, anti species, protA, Streptavidin), labeled with donor.
