Isolated from fermentation filtrates of Streptomyces avidinii, 1 mg of streptavidin binds approximately 10 µg of biotin. The preparations are supplied ready to use in 50 mmol/L Tris-HCl buffered saline solution. For assays that require a high EDTA concentration, a high temperature or a pH below 7, the W8044 series of Europium chelates is a better choice because of their greater stability.

Generic LANCE® reagents are intended for setting up homogeneous time-resolved fluorescence resonance energy transfer (TR-FRET) based assays using Eu-Chelate label as a donor and APC-labeled reagent as an acceptor. Generic reagents facilitate setting up LANCE® assays when there is a limited amount of specific reagents available or the assay reagents are relatively unstable. To enable optimization of both the signal or the noise ratio and signal stability, some of the generic reagents are labeled with two different chelates, W1024 or W8044.

LANCE® (Lanthanide chelate excite) and LANCE® Ultra are our TR-FRET (time-resolved fluorescence resonance energy transfer), homogeneous (no wash) technologies. One molecule of interest is labeled with a donor fluorophore (a LANCE Europium chelate) and the second molecule is labeled with an acceptor fluorophore [ULight™ dye, allophycocyanin (APC), etc.]. Upon excitation at 320 or 340 nm, energy can be transferred from the donor Europium chelate to the acceptor fluorophore if sufficiently close for FRET (~10 nm). This results in the emission of light at 665 nm (for ULight dye and APC).